The presence of pesticide residues in pears is a serious health concern. This study presents the results from a 2-year investigation (2013-2014) that used gas chromatography, GS/MS and UPLC/MS-MS to measure the leve...The presence of pesticide residues in pears is a serious health concern. This study presents the results from a 2-year investigation (2013-2014) that used gas chromatography, GS/MS and UPLC/MS-MS to measure the levels of 104 pesti- cides in 310 pear samples. In 93.2% of the samples, 43 pesticides were detected, of which the maximum residue levels (MRLs) were exceeded in 2.6% of the samples. Multiple residues (two to eight compounds) were present in 69.7% of the samples; one sample contained nine pesticides and one sample contained 10. Only 6.8% of the samples did not contain residues. To assess the health risks, the pesticide residue data have been combined with daily pear consumption data for children and adult populations. A deterministic model was used to assess the chronic and acute exposures based on the Joint Meeting on Pesticide Residues (JMPR) method. A potential acute risk was demonstrated for children in the case of bifenthrin, which was found to be present at 105.36% of the acute reference dose (ARfD) value. The long- term exposure of the Chinese consumer to pesticide residues through the consumption of raw pears was far below the acceptable daily intake (ADI) criterion. Additionally, the matrix ranking scheme was used to classify risk subgroups of pesticides and pear samples. In general, 95.5% of samples were deemed to be safe and nine pesticides were classified as being of a relatively high risk. The findings indicated that the occurrence of pesticide residues in pears should not be considered a serious public health problem. Nevertheless, a more detailed study is required for vulnerable consumer groups, especially children. Continuous monitoring of pesticides in pears and tighter regulation of pesticide residue standards are recommended.展开更多
The Yali pear(Pyrus bretschneideri Rehd.) is susceptible to superficial scald during prolonged cold storage and at shelf life. This study investigated the effects of 1-methylcyclopropene(1-MCP) and modified atmosp...The Yali pear(Pyrus bretschneideri Rehd.) is susceptible to superficial scald during prolonged cold storage and at shelf life. This study investigated the effects of 1-methylcyclopropene(1-MCP) and modified atmosphere packaging(MAP) on changes of fruit quality and superficial scald during cold storage and at shelf life in Yali pear. Compared with MAP, the combination of MAP and 1-MCP(MAP+1-MCP) treatment reduced the carbon dioxide and ethylene content inside the packaging bag. The 1-MCP, MAP, and MAP+1-MCP treatments reduced the superficial scald index, malondialdehyde content, O2^-· production rate and relative conductivity and inhibited the accumulation of α-farnesene and conjugated trienes in the peel. 1-MCP and MAP+1-MCP treatments maintained a higher phenolic content and enhanced the catalase and superoxide dismutase activities in the fruit, while reduced activities of lipoxygenase and polyphenol oxidase in the peel preceding the onset of superficial scald. Comprehensive analysis indicated that the MAP+1-MCP treatment is the most effective method tested for improving the quality of Yali pears during cold storage and at shelf life.展开更多
Maintenance of green color is the primary indicator of quality in the market evaluation of Korla Xiang pears at present and can generally be achieved through early harvesting and decreasing the storage temperature, bu...Maintenance of green color is the primary indicator of quality in the market evaluation of Korla Xiang pears at present and can generally be achieved through early harvesting and decreasing the storage temperature, but the fruit quality was reduced by early harvesting, and the decreasing storage temperature increased the risk of chilling injury. The objectives of this study were to determine the optimal storage parameters for different storage times and to find ways to preserve the green skin color of pears. Specifically, we analyzed the effects of the ethylene inhibitor, 1-methylcyclopropene (1-MCP), combined with low temperature on quality and maintenance of the green color of Korla Xiang pears during storage. We found that 1-MCP and/or low temperature reduced the loss of green color at 20℃ after being removed from cold storage. In addition, 1-MCP significantly inhibited the decline of titratable acid and ascorbic acid but had no significant effect on fruit firmness and total soluble solids. Low temperature with or without 1-MCP inhibited the release of ethylene, inhibited the decline in the stalk preservation index, inhibited the increase in decay rate and weight loss rate during storage, and inhibited the increase in the core browning index after 225 days of storage. Different storage temperatures had different effects on the quality of Korla Xiang pears. Despite inhibiting ethylene release, a storage temperature of-1.5℃ increased the respiration rate. Storage at -1.5℃ caused core browning eady during storage due to chilling injury, whereas at 2℃ core browning occurred late during storage due to senescence. In late storage, 1-MCP had no significant effect on the maintenance of Korla Xiang pear quality at 2℃. Based on these results, we determined the optimal combinations of low temperature and 1-MCP treatment to maintain pear quality while avoiding chilling injury. For different marketing times, the optimal conditions for storage until New Year's Day (a storage duration of 90 days) are 2℃ or 1-MCP combined with 2℃. For storage until the Spring Festival (a storage duration of 150 days), the optimal conditions are 0℃ or 1-MCP combined with 0℃, and for storage until May (a storage duration of 225 days), the best conditions are 1-MCP combined with -1.5℃.展开更多
The danger of mycotoxin contamination entering the food supply through post-harvest infection is of perennial concern to food safety experts. To explore the distribution of Penicillium expansum and diffusion of its my...The danger of mycotoxin contamination entering the food supply through post-harvest infection is of perennial concern to food safety experts. To explore the distribution of Penicillium expansum and diffusion of its mycotoxin, patulin, in blue mold-damaged pears, Pyrus bretschneideri Rehd. cv. Yali obtained from markets and orchards in China were artificially inoculated with P. expansum and assayed for patulin accumulation and degree of fungal colonization. The inoculated pears were incubated until the lesions were 5, 10, 20, or 30 mm in diameter. We sampled tissue at a range of distances from the lesion, measured the spread of Penicillium by plate colony-counting methods, and used UHPLC-MS/MS to detect and quantify the patulin concentration. More P. expansum colony-forming units were isolated from pears with a higher degree of decay. Farther from the lesion, the fewer P. expansum colonies were observed, and the lower the patulin content detected. We found a significant difference in the patulin content between samples due to lesion size, and also in tissue sampled 10 mm away from the lesion. In consideration of this finding, to ensure food safety, we recommend that when a blue mold rot lesion on pear is 5, 10, or 20 mm in diameter, 20, 30, and 40 mm beyond the lesion should be removed, respectively. If a lesion surpasses 30 mm in diameter, the whole pear should be thrown away.展开更多
The effect of fumigation with 10, 20, and 30 μL L-1 nitric oxide (NO) was investigated to study the effects of NO on the quality of Yali pears during cold storage. The ethylene production, composition of cell walls...The effect of fumigation with 10, 20, and 30 μL L-1 nitric oxide (NO) was investigated to study the effects of NO on the quality of Yali pears during cold storage. The ethylene production, composition of cell walls, and cell-wall-modifying enzyme activities were measured on fruits which were fumigated with NO (20 μL L-1). The results showed that NO not only reduced the peak value of ethylene production rate, the soluble sugar, soluble solid content, maintained higher firmness, starch, and NO content, but also retarded the degradation of covalent soluble pectin, accumulation of ionic soluble pectin and water soluble pectin. Moreover, NO fumigation decreased the activities of polygalacturonase (PG) and b-galactosidase(b-Gal) and delayed the peak of PG activity of fruits. Therefore, it indicated that NO fumigation could delay the softening and ripening of Yali pears.展开更多
Studies were conducted over the effects of 1-methylcycolpropene (1-MCP) treatment on postharvest life of Suli pears (Pyrus bretschneideri Rehd.) stored at room and cold temperatures on nitric oxide (NO),nitric o...Studies were conducted over the effects of 1-methylcycolpropene (1-MCP) treatment on postharvest life of Suli pears (Pyrus bretschneideri Rehd.) stored at room and cold temperatures on nitric oxide (NO),nitric oxide synthase (NOS) activity,and hydrogen dioxide (H2O2).Results showed that the 1-MCP treatment had little effect on total soluble solids (TSS) at both room and cold temperatures.1-MCP delayed softening of Suli pear fruits,decreased respiratory rate and H2O2 accumulation,and increased NO and NOS activity at room temperature storage,while the effect of cold temperature storage was relatively inferior.There was a significant positive correlation between NOS activity and NO content.It is concluded that 1-MCP had effects on endogenous NO content and accumulation of H2O2.Similarly,H2O2 acting as a signaling molecule via regulating NO level affects the ripening and senescence of Suli pears.展开更多
Bleeding canker,a devastating disease of pear trees(Pyrus pyrifolia L.),was first reported in the 1970 s in Jiangsu,China and more recently in other provinces in China.Trees infected with bleeding canker pathogen,Dick...Bleeding canker,a devastating disease of pear trees(Pyrus pyrifolia L.),was first reported in the 1970 s in Jiangsu,China and more recently in other provinces in China.Trees infected with bleeding canker pathogen,Dickeya fangzhongdai,develop cankers on the trunks and branches,and a rust-colored mixture of bacterial ooze and tree sap could be seen all over the trunks and branches.In this study,we provided detail descriptions of the symptoms and epidemiology of bleeding canker disease.Based on pathogenic and phenotypic characterizations,we identified the causal agent of bleeding canker of pear as D.fangzhongdai.Dickeya fangzhongdai strains isolated from pear were also pathogenic on Solanum tuberosum,Brassica pekinensis,Lycopersicon esculentum,and Phalaenopsis aphrodite based on artificial inoculation,and the pathogen were more virulent on potato than that of D.solani strain.This study provides new information about this disease and bleeding canker disease of pear.展开更多
In order to better design, fabricate and control pear handling machine, we should take into account mechanical and rheological properties of pear fruits as related to handling process. The changes in rheological prope...In order to better design, fabricate and control pear handling machine, we should take into account mechanical and rheological properties of pear fruits as related to handling process. The changes in rheological properties of pears stored at 5, 15, 25 ℃ and variable (fluctuating) temperature for 12 days were evaluated in terms of elasticity and viscosity parameters using creep tests. The elasticity and viscosity parameters in creep tests in general decreased with increase in storage time both under constant and variable storage conditions. For the variable storage condition, a bulk mean temperature calculated to account for a series combination of storage time and temperature to which the pears subjected. The changes in rheological properties due to variable storage temperature were described as a function of storage time. The result indicated that except the viscosity parameter of the Maxwell component of the four-element model, it was possible to describe the changes in rheological properties as a function of storage time, which are better physical parameters to estimate the quality of pears.展开更多
Fruitlet calyx shedding in pear plants is apparently regulated via numerous pathways that involve both environmental triggers and phytohormones cues such as auxin. In this study, we found at 10 days after full bloom (...Fruitlet calyx shedding in pear plants is apparently regulated via numerous pathways that involve both environmental triggers and phytohormones cues such as auxin. In this study, we found at 10 days after full bloom (DAFB) higher levels of indoleacetic acid (IAA) and tryptophan (Trp) in calyx persistence fruitlet (CPF) than calyx shedding fruitlet (CSF) ofDanshan Suli’ pear (Pyrus bretschneideri Rhed.). Consisting with this, the activity of indolealdehyde oxidase (IAAIdO), which promotes IAA synthesis, was remarkably increased, and that of peroxidase(POD), which degrades IAA, dropped markedly in CPF but not in CSF. Further, qRT-PCR results revealed that most of 31 PbrARFs (encoding auxin response factors) in Pyrus bretschneideri were highly expressed in CPF, whereas PbrARF4, PbrARF24 and PbrARF26 were significantly downregulated in CPF vis-a-vis CSF. Phylogenetic analysis revealed that 6 PbrARFs clustered in the group III, where PbrARF4 showed the closest affinity with AtARF1 that promotes organ abscission, indicating a putative role of PbrARF4 in mediating the process of calyx shedding in pear. In fact, the ectopic overexpression of PbrARF4 in Solanum lycopersicum resulted in an earlier-formed and deeper abscission layer (AL) in the transgenic plants, whose calyxes were more prone to wilt at the mature red stage (MR) compared with the control plants (wild-type). More importantly, expression levels of the abscission genes SILS and Sl Cel2 in transgenic plants overexpressing PbrARF4 were significantly upregulated in comparation with the WT, whereas those of Sl BI and Sl TAPG2 were considerably inhibited. Further, PbrJOINTLESS and PbrIDA,the two genes related to calyx shedding in pear, were up-regulated more in CSF than CPF. The findings contribute to a better understanding of PbrARFs involved in fruitlet calyx shedding of pear, which could prove beneficial to improving the quality of pear fruit.展开更多
The Arabidopsis Toxicos en Levadura(ATL)protein is a subfamily of the E3 ubiquitin ligases,which exists widely in plants and is extensively involved in plant growth and development.Although the ATL family has been ide...The Arabidopsis Toxicos en Levadura(ATL)protein is a subfamily of the E3 ubiquitin ligases,which exists widely in plants and is extensively involved in plant growth and development.Although the ATL family has been identified in other species,such as Arabidopsis,Oryza sativa,and grapevine,few reports on pear ATL gene families have been reported.In this study,92 PbrATL genes were identified and analyzed from the Pyrus breschneideri genome.Motif analysis and phylogenetic tree generation divided them into nine subgroups,and chromosome localization analysis showed that the 92 PbrATL genes were distributed in 16 of 17 pear chromosomes.Transcriptome data and quantitative real-time polymerase chain reaction(qRT-PCR)experiments demonstrated that PbrATL18,PbrATL41,and PbrATL88 were involved in both pear drought resistance and Colletotrichum fructicola infection.In addition,Arabidopsis thaliana overexpressing PbrATL18 showed greater resistance to drought stress than the wild type(WT),and PbrATL18-silenced pear seedlings showed greater sensitivity to drought and C.fructicola infection than the controls.PbrATL18 regulated plant resistance by regulating chitinase(CHI),phenylalanine ammonia-lyase(PAL),polyphenol oxidase(PPO),catalase(CAT),peroxidase(POD),and superoxide dismutase(SOD)activities.This study provided a reference for further exploring the functions of the PbrATL gene in drought resistance and C.fructicola infection.展开更多
The red coloring of pear fruits is mainly caused by anthocyanin accumulation. Red sport, represented by the green pear cultivar ‘Bartlett’(BL) and the red-skinned derivative ‘Max Red Bartlett’(MRB), is an ideal ma...The red coloring of pear fruits is mainly caused by anthocyanin accumulation. Red sport, represented by the green pear cultivar ‘Bartlett’(BL) and the red-skinned derivative ‘Max Red Bartlett’(MRB), is an ideal material for studying the molecular mechanism of anthocyanin accumulation in pear. Genetic analysis has previously revealed a quantitative trait locus(QTL) associated with red skin color in MRB. However, the key gene in the QTL and the associated regulatory mechanism remain unknown. In the present study, transcriptomic and methylomic analyses were performed using pear skin for comparisons between BL and MRB. These analyses revealed differential PcHY5 DNA methylation levels between the two cultivars;MRB had lower PcHY5 methylation than BL during fruit development, and PcHY5 was more highly expressed in MRB than in BL. These results indicated that PcHY5 is involved in the variations in skin color between BL and MRB. We further used dual luciferase assays to verify that PcHY5 activates the promoters of the anthocyanin biosynthesis and transport genes PcUFGT, PcGST, PcMYB10 and PcMYB114, confirming that PcHY5 not only regulates anthocyanin biosynthesis but also anthocyanin transport. Furthermore, we analyzed a key differentially methylated site between MRB and BL, and found that it was located in an intronic region of PcHY5. The lower methylation levels in this PcHY5 intron in MRB were associated with red fruit color during development, whereas the higher methylation levels at the same site in BL were associated with green fruit color. Based on the differential expression and methylation patterns in PcHY5 and gene functional verification, we hypothesize that PcHY5, which is regulated by methylation levels, affects anthocyanin biosynthesis and transport to cause the variations in skin color between BL and MRB.展开更多
Early defoliation,which usually occurs during summer in pear trees,is gradually becoming a major problem that poses a serious threat to the pear industry in southern China.However,there is no system for evaluating the...Early defoliation,which usually occurs during summer in pear trees,is gradually becoming a major problem that poses a serious threat to the pear industry in southern China.However,there is no system for evaluating the responses of different cultivars to early defoliation,and our knowledge of the potential molecular regulation of the genes underlying this phenomenon is still limited.In this study,we conducted field investigations of 155 pear accessions to assess their resistance or susceptibility to early defoliation.A total of 126 accessions were found to be susceptible to early defoliation,and only 29 accessions were resistant.Among them,19 resistant accessions belong to the sand pear species(Pyrus pyrifolia).To identify the resistance genes related to early defoliation,the healthy and diseased samples of two sand pear accessions,namely,the resistant early defoliation accession‘Whasan’and the susceptible early defoliation accession‘Cuiguan’,were used to perform RNA sequencing.Compared with‘Cuiguan’,a total of 444 genes were uniquely differentially expressed in‘Whasan’.Combined with GO and KEGG enrichment analyses,we found that early defoliation was closely related to the stress response.Furthermore,a weighted gene co-expression network analysis revealed a high correlation of WRKY and ethylene responsive factor(ERF)transcription factors with early defoliation resistance.This study provides useful resistant germplasm resources and new insights into potentially essential genes that respond to early defoliation in pears,which may facilitate a better understanding of the resistance mechanism and molecular breeding of resistant pear cultivars.展开更多
The pear(Pyrus spp.)is well known for diverse flavors,textures,and global horticultural importance.However,the genetic diversity responsible for its extensive phenotypic variations remains largely unexplored.Here,we d...The pear(Pyrus spp.)is well known for diverse flavors,textures,and global horticultural importance.However,the genetic diversity responsible for its extensive phenotypic variations remains largely unexplored.Here,we de novo assembled and annotated the genomes of the maternal(PsbM)and paternal(PsbF)lines of the hybrid‘Yuluxiang'pear and constructed the pear pangenome of 1.15 Gb by combining these two genomes with five previously published pear genomes representing cultivated and wild germplasm.Using the constructed pangenome,we identified 21224 gene PAVs(Presence-absence variation)and 1158812 SNPs(Single Nucleotide Polymorphism)in the non-reference genome that were absent in the PsbM reference genome.Compared with SNP markers,PAV-based analysis provides additional insights into the pear population structure.In addition,some genes associated with pear fruit quality traits have differential occurrence frequencies and differential gene expression between Asian and European populations.Moreover,our analysis of the pear pangenome revealed a mutated SNP and an insertion in the promoter region of the gene PsbMGH3.1 potentially enhance sepal shedding in‘Xuehuali'which is vital for pear quality.PsbMGH3.1 may play a role in the IAA pathway,contributing to a distinct low-auxin phenotype observed in plants by heterologously overexpressing this gene.This research helps capture the genetic diversity of pear populations and provides genomic resources for accelerating breeding.展开更多
Genomic selection (GS) has the potential to improve selection efficiency and shorten the breeding cycle in fruit tree breeding. In this study,we evaluated the effect of prediction methods, marker density and the train...Genomic selection (GS) has the potential to improve selection efficiency and shorten the breeding cycle in fruit tree breeding. In this study,we evaluated the effect of prediction methods, marker density and the training population (TP) size on pear GS for improving its performance and reducing cost. We evaluated GS under two scenarios:(1) five-fold cross-validation in an interspecific pear family;(2) independent validation. Based on the cross-validation scheme, the prediction accuracy (PA) of eight fruit traits varied between 0.33 (fruit core vertical diameter)and 0.65 (stone cell content). Except for single fruit weight, a slightly better prediction accuracy (PA) was observed for the five parametrical methods compared with the two non-parametrical methods. In our TP of 310 individuals, 2 000 single nucleotide polymorphism (SNP) markers were sufficient to make reasonably accurate predictions. PAs for different traits increased by 18.21%-46.98%when the TP size increased from 50to 100, but the increment was smaller (-4.13%-33.91%) when the TP size increased from 200 to 250. For independent validation, the PAs ranged from 0.11 to 0.45 using rrBLUP method. In summary, our results showed that the TP size and SNP numbers had a greater impact on the PA than prediction methods. Furthermore, relatedness among the training and validation sets, and the complexity of traits should be considered when designing a TP to predict the test panel.展开更多
During storage at 20℃,specific pear cultivars may exhibit a greasy texture and decline in quality due to fruit senescence.Among these varieties,‘Yuluxiang’is particularly susceptible to peel greasiness,resulting in...During storage at 20℃,specific pear cultivars may exhibit a greasy texture and decline in quality due to fruit senescence.Among these varieties,‘Yuluxiang’is particularly susceptible to peel greasiness,resulting in significant economic losses.Therefore,there is an urgent need for a preservative that can effectively inhibit the development of greasiness.Previous studies have demonstrated the efficacy of 1-methylcyclopropene(1-MCP)in extending the storage period of fruits.We hypothesize that it may also influence the occurrence of postharvest peel greasiness in the‘Yuluxiang’pears.In this study,we treated‘Yuluxiang’pears with 1-MCP.We stored them at 20℃while analyzing the composition and morphology of the surface waxes,recording enzyme activities related to wax synthesis,and measuring indicators associated with fruit storage quality and physiological characteristics.The results demonstrate that prolonged storage at 20℃leads to a rapid increase in skin greasiness,consistent with the observed elevations in L^(*),greasiness score,and the content of total wax and greasy wax components.Moreover,there were indications that cuticular waxes underwent melting,resulting in the formation of an amorphous structure.In comparison to controls,the application of 1-MCP significantly inhibited increments in L^(*) values as well as grease scores while also reducing accumulation rates for oily waxes throughout most stages over its shelf period,additionally delaying transitions from flaky-wax structures towards their amorphous counterparts.During the initial 7 d of storage,several enzymes involved in the biosynthesis and metabolism of greasy wax components,including lipoxygenase(LOX),phospholipase D(PLD),andβ-ketoacyl-CoA synthase(KCS),exhibited an increase followed by a subsequent decline.The activity of LOX during early shelf life(0–7 d)and the KCS activity during middle to late shelf life(14–21 d)were significantly suppressed by 1-MCP.Additionally,1-MCP effectively maintained firmness,total soluble solid(TSS)and titratable acid(TA)contents,peroxidase(POD),and phenylalanine ammonia-lyase(PAL)activities while inhibiting vitamin C degradation and weight loss.Furthermore,it restrained polyphenol oxidase(PPO)activity,ethylene production,and respiration rate increase.These findings demonstrate that 1-MCP not only delays the onset of peel greasiness but also preserves the overall storage quality of‘Yuluxiang’pear at a temperature of 20℃.This study presents a novel approach for developing new preservatives to inhibit pear fruit peel greasiness and provides a theoretical foundation for further research on pear fruit preservation.展开更多
As a cell proliferation regulator involved in wide biological processes in plants,GRF-INTERACTING FACTOR(GIF)controls different tissues development.However,whether GIF participates in fruit development remains unclear...As a cell proliferation regulator involved in wide biological processes in plants,GRF-INTERACTING FACTOR(GIF)controls different tissues development.However,whether GIF participates in fruit development remains unclear.According to transcriptome data,we identified PbGIF1was highly expressed during fruit development in cytokinins induced parthenocarpy pear.In the present study,the biofunction of PbGIF1 was initially verified.Overexpression of PbGIF1 promoted fruit size of transgenic tomato.The size of flesh fruit was not affected by cell expansion but the cell proliferation was promoted by overexpressing Pb GIF1.The accelerated cell proliferation process was also observed in PbGIF1-overexpressed transgenic pear fruit calli.The transcriptional regulation of cytokinins on PbGIF1 was further confirmed by exogenous CPPU treatments in pear fruitlets.To investigate the underlying mechanism,the cytokinins-responded factor,PbRR1,was further focused on.The results of Yeast-one-hybrid assay suggested that PbRR1 can bind to the promoter sequence of PbGIF1.The transcriptional activation of PbRR1 on PbGIF1 was also confirmed by Dual-Luciferase assays.Taken together,the results showed that cytokinins control pear fruit development via the transcriptional activation of PbGIF1 by PbRR1.展开更多
Drought stress is a devastating natural disaster driven by the continuing intensification of global warming,which seriously threatens the productivity and quality of several horticultural crops,including pear.Gibberel...Drought stress is a devastating natural disaster driven by the continuing intensification of global warming,which seriously threatens the productivity and quality of several horticultural crops,including pear.Gibberellins(GAs)play crucial roles in plant growth,development,and responses to drought stress.Previous studies have shown significant reductions of GA levels in plants under drought stress;however,our understanding of the intrinsic regulation mechanisms of GA-mediated drought stress in pear remains very limited.Here,we show that drought stress can impair the accumulation of bioactive GAs(BGAs),and subsequently identified PbrGA2ox1 as a chloroplast-localized GA deactivation gene.This gene was significantly induced by drought stress and abscisic acid(ABA)treatment,but was suppressed by GA_(3)treatment.PbrGA2ox1-overexpressing transgenic tobacco plants(Nicotiana benthamiana)exhibited enhanced tolerance to dehydration and drought stresses,whereas knock-down of PbrGA2ox1 in pear(Pyrus betulaefolia)by virus-induced gene silencing led to elevated drought sensitivity.Transgenic plants were hypersensitive to ABA,and had a lower BGAs content,enhanced reactive oxygen species(ROS)scavenging ability,and augmented ABA accumulation and signaling under drought stress compared to wild-type plants.However,the opposite effects were observed with PbrGA2ox1 silencing in pear.Moreover,exogenous GA_(3)treatment aggravated the ROS toxic effect and restrained ABA synthesis and signaling,resulting in the compromised drought tolerance of pear.In summary,our results shed light on the mechanism by which BGAs are eliminated in pear leaves under drought stress,providing further insights into the mechanism regulating the effects of GA on the drought tolerance of plants.展开更多
基金financially supported by the National Program for Quality and Safety Risk Assessment of Agricultural Products of China (GJFP2014002, GJFP2015002)the Core Research Budget of the Non-Profit Governmental Research Institution of China (0032014013)
文摘The presence of pesticide residues in pears is a serious health concern. This study presents the results from a 2-year investigation (2013-2014) that used gas chromatography, GS/MS and UPLC/MS-MS to measure the levels of 104 pesti- cides in 310 pear samples. In 93.2% of the samples, 43 pesticides were detected, of which the maximum residue levels (MRLs) were exceeded in 2.6% of the samples. Multiple residues (two to eight compounds) were present in 69.7% of the samples; one sample contained nine pesticides and one sample contained 10. Only 6.8% of the samples did not contain residues. To assess the health risks, the pesticide residue data have been combined with daily pear consumption data for children and adult populations. A deterministic model was used to assess the chronic and acute exposures based on the Joint Meeting on Pesticide Residues (JMPR) method. A potential acute risk was demonstrated for children in the case of bifenthrin, which was found to be present at 105.36% of the acute reference dose (ARfD) value. The long- term exposure of the Chinese consumer to pesticide residues through the consumption of raw pears was far below the acceptable daily intake (ADI) criterion. Additionally, the matrix ranking scheme was used to classify risk subgroups of pesticides and pear samples. In general, 95.5% of samples were deemed to be safe and nine pesticides were classified as being of a relatively high risk. The findings indicated that the occurrence of pesticide residues in pears should not be considered a serious public health problem. Nevertheless, a more detailed study is required for vulnerable consumer groups, especially children. Continuous monitoring of pesticides in pears and tighter regulation of pesticide residue standards are recommended.
基金supported by the emarked fund for the China Agriculture Research System for National Technology System for Pear Industry(CARS-28-22)the Innovation Project of Modern Agricultural Sciences and Technology of Hebei Province,China(494-0402-YSN-C8RA)+1 种基金the Youth Fund of Hebei Academy of Agriculture and Forestry Sciences,China(A2015110106)the Finance Special Foundation of Hebei Province,China(494-0402-YBN-0G4L)
文摘The Yali pear(Pyrus bretschneideri Rehd.) is susceptible to superficial scald during prolonged cold storage and at shelf life. This study investigated the effects of 1-methylcyclopropene(1-MCP) and modified atmosphere packaging(MAP) on changes of fruit quality and superficial scald during cold storage and at shelf life in Yali pear. Compared with MAP, the combination of MAP and 1-MCP(MAP+1-MCP) treatment reduced the carbon dioxide and ethylene content inside the packaging bag. The 1-MCP, MAP, and MAP+1-MCP treatments reduced the superficial scald index, malondialdehyde content, O2^-· production rate and relative conductivity and inhibited the accumulation of α-farnesene and conjugated trienes in the peel. 1-MCP and MAP+1-MCP treatments maintained a higher phenolic content and enhanced the catalase and superoxide dismutase activities in the fruit, while reduced activities of lipoxygenase and polyphenol oxidase in the peel preceding the onset of superficial scald. Comprehensive analysis indicated that the MAP+1-MCP treatment is the most effective method tested for improving the quality of Yali pears during cold storage and at shelf life.
基金supported by a grant from the National Key R&D Program of China (2016YFD0400903-06)the emarked fund for China Agriculture Research System (CARS-29-19)the Agricultural Science and Technology Innovation Program of the Chinese Academy of Agricultural Sciences (CAAS-ASTIP-2016-RIP-06)
文摘Maintenance of green color is the primary indicator of quality in the market evaluation of Korla Xiang pears at present and can generally be achieved through early harvesting and decreasing the storage temperature, but the fruit quality was reduced by early harvesting, and the decreasing storage temperature increased the risk of chilling injury. The objectives of this study were to determine the optimal storage parameters for different storage times and to find ways to preserve the green skin color of pears. Specifically, we analyzed the effects of the ethylene inhibitor, 1-methylcyclopropene (1-MCP), combined with low temperature on quality and maintenance of the green color of Korla Xiang pears during storage. We found that 1-MCP and/or low temperature reduced the loss of green color at 20℃ after being removed from cold storage. In addition, 1-MCP significantly inhibited the decline of titratable acid and ascorbic acid but had no significant effect on fruit firmness and total soluble solids. Low temperature with or without 1-MCP inhibited the release of ethylene, inhibited the decline in the stalk preservation index, inhibited the increase in decay rate and weight loss rate during storage, and inhibited the increase in the core browning index after 225 days of storage. Different storage temperatures had different effects on the quality of Korla Xiang pears. Despite inhibiting ethylene release, a storage temperature of-1.5℃ increased the respiration rate. Storage at -1.5℃ caused core browning eady during storage due to chilling injury, whereas at 2℃ core browning occurred late during storage due to senescence. In late storage, 1-MCP had no significant effect on the maintenance of Korla Xiang pear quality at 2℃. Based on these results, we determined the optimal combinations of low temperature and 1-MCP treatment to maintain pear quality while avoiding chilling injury. For different marketing times, the optimal conditions for storage until New Year's Day (a storage duration of 90 days) are 2℃ or 1-MCP combined with 2℃. For storage until the Spring Festival (a storage duration of 150 days), the optimal conditions are 0℃ or 1-MCP combined with 0℃, and for storage until May (a storage duration of 225 days), the best conditions are 1-MCP combined with -1.5℃.
基金supported by the Quality and Safety Risk Assessment for Agro-products of China (GJFP 2015014)
文摘The danger of mycotoxin contamination entering the food supply through post-harvest infection is of perennial concern to food safety experts. To explore the distribution of Penicillium expansum and diffusion of its mycotoxin, patulin, in blue mold-damaged pears, Pyrus bretschneideri Rehd. cv. Yali obtained from markets and orchards in China were artificially inoculated with P. expansum and assayed for patulin accumulation and degree of fungal colonization. The inoculated pears were incubated until the lesions were 5, 10, 20, or 30 mm in diameter. We sampled tissue at a range of distances from the lesion, measured the spread of Penicillium by plate colony-counting methods, and used UHPLC-MS/MS to detect and quantify the patulin concentration. More P. expansum colony-forming units were isolated from pears with a higher degree of decay. Farther from the lesion, the fewer P. expansum colonies were observed, and the lower the patulin content detected. We found a significant difference in the patulin content between samples due to lesion size, and also in tissue sampled 10 mm away from the lesion. In consideration of this finding, to ensure food safety, we recommend that when a blue mold rot lesion on pear is 5, 10, or 20 mm in diameter, 20, 30, and 40 mm beyond the lesion should be removed, respectively. If a lesion surpasses 30 mm in diameter, the whole pear should be thrown away.
基金supported by the Earmarked Found for Modern Pear-Industry Technology Research System (nycytx-29-19)
文摘The effect of fumigation with 10, 20, and 30 μL L-1 nitric oxide (NO) was investigated to study the effects of NO on the quality of Yali pears during cold storage. The ethylene production, composition of cell walls, and cell-wall-modifying enzyme activities were measured on fruits which were fumigated with NO (20 μL L-1). The results showed that NO not only reduced the peak value of ethylene production rate, the soluble sugar, soluble solid content, maintained higher firmness, starch, and NO content, but also retarded the degradation of covalent soluble pectin, accumulation of ionic soluble pectin and water soluble pectin. Moreover, NO fumigation decreased the activities of polygalacturonase (PG) and b-galactosidase(b-Gal) and delayed the peak of PG activity of fruits. Therefore, it indicated that NO fumigation could delay the softening and ripening of Yali pears.
基金supported by the Earmarked Fund for Modern Pear-Industry Technology Research System of China (nycytx-29-19)
文摘Studies were conducted over the effects of 1-methylcycolpropene (1-MCP) treatment on postharvest life of Suli pears (Pyrus bretschneideri Rehd.) stored at room and cold temperatures on nitric oxide (NO),nitric oxide synthase (NOS) activity,and hydrogen dioxide (H2O2).Results showed that the 1-MCP treatment had little effect on total soluble solids (TSS) at both room and cold temperatures.1-MCP delayed softening of Suli pear fruits,decreased respiratory rate and H2O2 accumulation,and increased NO and NOS activity at room temperature storage,while the effect of cold temperature storage was relatively inferior.There was a significant positive correlation between NOS activity and NO content.It is concluded that 1-MCP had effects on endogenous NO content and accumulation of H2O2.Similarly,H2O2 acting as a signaling molecule via regulating NO level affects the ripening and senescence of Suli pears.
基金supported by the 111 International Cooperation Grant 2.0(BP0719029)to Nanjing Agricultural University,China,from the Chinese government and Canadian Interdepartmental funding of Genomics Research and Development Initiatives(GRDI)。
文摘Bleeding canker,a devastating disease of pear trees(Pyrus pyrifolia L.),was first reported in the 1970 s in Jiangsu,China and more recently in other provinces in China.Trees infected with bleeding canker pathogen,Dickeya fangzhongdai,develop cankers on the trunks and branches,and a rust-colored mixture of bacterial ooze and tree sap could be seen all over the trunks and branches.In this study,we provided detail descriptions of the symptoms and epidemiology of bleeding canker disease.Based on pathogenic and phenotypic characterizations,we identified the causal agent of bleeding canker of pear as D.fangzhongdai.Dickeya fangzhongdai strains isolated from pear were also pathogenic on Solanum tuberosum,Brassica pekinensis,Lycopersicon esculentum,and Phalaenopsis aphrodite based on artificial inoculation,and the pathogen were more virulent on potato than that of D.solani strain.This study provides new information about this disease and bleeding canker disease of pear.
文摘In order to better design, fabricate and control pear handling machine, we should take into account mechanical and rheological properties of pear fruits as related to handling process. The changes in rheological properties of pears stored at 5, 15, 25 ℃ and variable (fluctuating) temperature for 12 days were evaluated in terms of elasticity and viscosity parameters using creep tests. The elasticity and viscosity parameters in creep tests in general decreased with increase in storage time both under constant and variable storage conditions. For the variable storage condition, a bulk mean temperature calculated to account for a series combination of storage time and temperature to which the pears subjected. The changes in rheological properties due to variable storage temperature were described as a function of storage time. The result indicated that except the viscosity parameter of the Maxwell component of the four-element model, it was possible to describe the changes in rheological properties as a function of storage time, which are better physical parameters to estimate the quality of pears.
基金supported by the China Agriculture Research System (Grant No.CARS-28-14)。
文摘Fruitlet calyx shedding in pear plants is apparently regulated via numerous pathways that involve both environmental triggers and phytohormones cues such as auxin. In this study, we found at 10 days after full bloom (DAFB) higher levels of indoleacetic acid (IAA) and tryptophan (Trp) in calyx persistence fruitlet (CPF) than calyx shedding fruitlet (CSF) ofDanshan Suli’ pear (Pyrus bretschneideri Rhed.). Consisting with this, the activity of indolealdehyde oxidase (IAAIdO), which promotes IAA synthesis, was remarkably increased, and that of peroxidase(POD), which degrades IAA, dropped markedly in CPF but not in CSF. Further, qRT-PCR results revealed that most of 31 PbrARFs (encoding auxin response factors) in Pyrus bretschneideri were highly expressed in CPF, whereas PbrARF4, PbrARF24 and PbrARF26 were significantly downregulated in CPF vis-a-vis CSF. Phylogenetic analysis revealed that 6 PbrARFs clustered in the group III, where PbrARF4 showed the closest affinity with AtARF1 that promotes organ abscission, indicating a putative role of PbrARF4 in mediating the process of calyx shedding in pear. In fact, the ectopic overexpression of PbrARF4 in Solanum lycopersicum resulted in an earlier-formed and deeper abscission layer (AL) in the transgenic plants, whose calyxes were more prone to wilt at the mature red stage (MR) compared with the control plants (wild-type). More importantly, expression levels of the abscission genes SILS and Sl Cel2 in transgenic plants overexpressing PbrARF4 were significantly upregulated in comparation with the WT, whereas those of Sl BI and Sl TAPG2 were considerably inhibited. Further, PbrJOINTLESS and PbrIDA,the two genes related to calyx shedding in pear, were up-regulated more in CSF than CPF. The findings contribute to a better understanding of PbrARFs involved in fruitlet calyx shedding of pear, which could prove beneficial to improving the quality of pear fruit.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFD1200503)Jiangsu Agriculture Science and Technology Innovation Fund[Grant No.CX(22)3046]+2 种基金the National Science Foundation of China(Grant No.32072538)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Earmarked Fund for China Agriculture Research System(Grant No.CARS-28).
文摘The Arabidopsis Toxicos en Levadura(ATL)protein is a subfamily of the E3 ubiquitin ligases,which exists widely in plants and is extensively involved in plant growth and development.Although the ATL family has been identified in other species,such as Arabidopsis,Oryza sativa,and grapevine,few reports on pear ATL gene families have been reported.In this study,92 PbrATL genes were identified and analyzed from the Pyrus breschneideri genome.Motif analysis and phylogenetic tree generation divided them into nine subgroups,and chromosome localization analysis showed that the 92 PbrATL genes were distributed in 16 of 17 pear chromosomes.Transcriptome data and quantitative real-time polymerase chain reaction(qRT-PCR)experiments demonstrated that PbrATL18,PbrATL41,and PbrATL88 were involved in both pear drought resistance and Colletotrichum fructicola infection.In addition,Arabidopsis thaliana overexpressing PbrATL18 showed greater resistance to drought stress than the wild type(WT),and PbrATL18-silenced pear seedlings showed greater sensitivity to drought and C.fructicola infection than the controls.PbrATL18 regulated plant resistance by regulating chitinase(CHI),phenylalanine ammonia-lyase(PAL),polyphenol oxidase(PPO),catalase(CAT),peroxidase(POD),and superoxide dismutase(SOD)activities.This study provided a reference for further exploring the functions of the PbrATL gene in drought resistance and C.fructicola infection.
基金supported by the National Natural Science Foundation of China (31820103012)the earmarked fund for China Agriculture Research System (CARS-28)the earmarked fund for Jiangsu Agricultural Industry Technology System,China (JATS[2022]454)。
文摘The red coloring of pear fruits is mainly caused by anthocyanin accumulation. Red sport, represented by the green pear cultivar ‘Bartlett’(BL) and the red-skinned derivative ‘Max Red Bartlett’(MRB), is an ideal material for studying the molecular mechanism of anthocyanin accumulation in pear. Genetic analysis has previously revealed a quantitative trait locus(QTL) associated with red skin color in MRB. However, the key gene in the QTL and the associated regulatory mechanism remain unknown. In the present study, transcriptomic and methylomic analyses were performed using pear skin for comparisons between BL and MRB. These analyses revealed differential PcHY5 DNA methylation levels between the two cultivars;MRB had lower PcHY5 methylation than BL during fruit development, and PcHY5 was more highly expressed in MRB than in BL. These results indicated that PcHY5 is involved in the variations in skin color between BL and MRB. We further used dual luciferase assays to verify that PcHY5 activates the promoters of the anthocyanin biosynthesis and transport genes PcUFGT, PcGST, PcMYB10 and PcMYB114, confirming that PcHY5 not only regulates anthocyanin biosynthesis but also anthocyanin transport. Furthermore, we analyzed a key differentially methylated site between MRB and BL, and found that it was located in an intronic region of PcHY5. The lower methylation levels in this PcHY5 intron in MRB were associated with red fruit color during development, whereas the higher methylation levels at the same site in BL were associated with green fruit color. Based on the differential expression and methylation patterns in PcHY5 and gene functional verification, we hypothesize that PcHY5, which is regulated by methylation levels, affects anthocyanin biosynthesis and transport to cause the variations in skin color between BL and MRB.
基金supported by the earmarked fund for Jiangsu Agricultural Industry Technology System,China(JATS[2021]453)the National Key Research and Development Program of China(2021YFD1200200)the earmarked fund for China Agriculture Research System(CARS-28).
文摘Early defoliation,which usually occurs during summer in pear trees,is gradually becoming a major problem that poses a serious threat to the pear industry in southern China.However,there is no system for evaluating the responses of different cultivars to early defoliation,and our knowledge of the potential molecular regulation of the genes underlying this phenomenon is still limited.In this study,we conducted field investigations of 155 pear accessions to assess their resistance or susceptibility to early defoliation.A total of 126 accessions were found to be susceptible to early defoliation,and only 29 accessions were resistant.Among them,19 resistant accessions belong to the sand pear species(Pyrus pyrifolia).To identify the resistance genes related to early defoliation,the healthy and diseased samples of two sand pear accessions,namely,the resistant early defoliation accession‘Whasan’and the susceptible early defoliation accession‘Cuiguan’,were used to perform RNA sequencing.Compared with‘Cuiguan’,a total of 444 genes were uniquely differentially expressed in‘Whasan’.Combined with GO and KEGG enrichment analyses,we found that early defoliation was closely related to the stress response.Furthermore,a weighted gene co-expression network analysis revealed a high correlation of WRKY and ethylene responsive factor(ERF)transcription factors with early defoliation resistance.This study provides useful resistant germplasm resources and new insights into potentially essential genes that respond to early defoliation in pears,which may facilitate a better understanding of the resistance mechanism and molecular breeding of resistant pear cultivars.
基金supported by the National Natural Science Foundation of China(Grant No.32102364)the General Program of Shandong Natural Science Foundation(Grant No.ZR2022MC064)+3 种基金the Shanxi Province Postdoctoral Research Activity Fund(Grant No.K462101001)the Doctoral Research Initiation Fund of Shanxi Datong University(Grant No.2023-B-15)the Earmarked Fund for Modern Agro-industry Technology Research System(Grant No.2023CYJSTX07)the Shanxi Province Excellent Doctoral Work Award Project(Grant No.606-02010609)。
文摘The pear(Pyrus spp.)is well known for diverse flavors,textures,and global horticultural importance.However,the genetic diversity responsible for its extensive phenotypic variations remains largely unexplored.Here,we de novo assembled and annotated the genomes of the maternal(PsbM)and paternal(PsbF)lines of the hybrid‘Yuluxiang'pear and constructed the pear pangenome of 1.15 Gb by combining these two genomes with five previously published pear genomes representing cultivated and wild germplasm.Using the constructed pangenome,we identified 21224 gene PAVs(Presence-absence variation)and 1158812 SNPs(Single Nucleotide Polymorphism)in the non-reference genome that were absent in the PsbM reference genome.Compared with SNP markers,PAV-based analysis provides additional insights into the pear population structure.In addition,some genes associated with pear fruit quality traits have differential occurrence frequencies and differential gene expression between Asian and European populations.Moreover,our analysis of the pear pangenome revealed a mutated SNP and an insertion in the promoter region of the gene PsbMGH3.1 potentially enhance sepal shedding in‘Xuehuali'which is vital for pear quality.PsbMGH3.1 may play a role in the IAA pathway,contributing to a distinct low-auxin phenotype observed in plants by heterologously overexpressing this gene.This research helps capture the genetic diversity of pear populations and provides genomic resources for accelerating breeding.
基金supported by the National Key Research and Development Program (Grant No.2022YFD1200503)Jiangsu Agricultural Science and Technology Innovation Fund [Grant No.CX(22)3043]+1 种基金the Earmarked Fund for China Agriculture Research System (Grant No.CARS-28)the Earmarked Fund for Jiangsu Agricultural Industry Technology System (Grant No.JATS [2022]454)。
文摘Genomic selection (GS) has the potential to improve selection efficiency and shorten the breeding cycle in fruit tree breeding. In this study,we evaluated the effect of prediction methods, marker density and the training population (TP) size on pear GS for improving its performance and reducing cost. We evaluated GS under two scenarios:(1) five-fold cross-validation in an interspecific pear family;(2) independent validation. Based on the cross-validation scheme, the prediction accuracy (PA) of eight fruit traits varied between 0.33 (fruit core vertical diameter)and 0.65 (stone cell content). Except for single fruit weight, a slightly better prediction accuracy (PA) was observed for the five parametrical methods compared with the two non-parametrical methods. In our TP of 310 individuals, 2 000 single nucleotide polymorphism (SNP) markers were sufficient to make reasonably accurate predictions. PAs for different traits increased by 18.21%-46.98%when the TP size increased from 50to 100, but the increment was smaller (-4.13%-33.91%) when the TP size increased from 200 to 250. For independent validation, the PAs ranged from 0.11 to 0.45 using rrBLUP method. In summary, our results showed that the TP size and SNP numbers had a greater impact on the PA than prediction methods. Furthermore, relatedness among the training and validation sets, and the complexity of traits should be considered when designing a TP to predict the test panel.
基金supported by the Agricultural Science and Technology Innovation Program of Chinese Academy of Agricultural Sciences(CAAS-ASTIP-RIP)the earmarked fund for the China Agriculture Research System(CARS-28)the Natural Science Foundation of Liaoning Province,China(2021-MS-036)。
文摘During storage at 20℃,specific pear cultivars may exhibit a greasy texture and decline in quality due to fruit senescence.Among these varieties,‘Yuluxiang’is particularly susceptible to peel greasiness,resulting in significant economic losses.Therefore,there is an urgent need for a preservative that can effectively inhibit the development of greasiness.Previous studies have demonstrated the efficacy of 1-methylcyclopropene(1-MCP)in extending the storage period of fruits.We hypothesize that it may also influence the occurrence of postharvest peel greasiness in the‘Yuluxiang’pears.In this study,we treated‘Yuluxiang’pears with 1-MCP.We stored them at 20℃while analyzing the composition and morphology of the surface waxes,recording enzyme activities related to wax synthesis,and measuring indicators associated with fruit storage quality and physiological characteristics.The results demonstrate that prolonged storage at 20℃leads to a rapid increase in skin greasiness,consistent with the observed elevations in L^(*),greasiness score,and the content of total wax and greasy wax components.Moreover,there were indications that cuticular waxes underwent melting,resulting in the formation of an amorphous structure.In comparison to controls,the application of 1-MCP significantly inhibited increments in L^(*) values as well as grease scores while also reducing accumulation rates for oily waxes throughout most stages over its shelf period,additionally delaying transitions from flaky-wax structures towards their amorphous counterparts.During the initial 7 d of storage,several enzymes involved in the biosynthesis and metabolism of greasy wax components,including lipoxygenase(LOX),phospholipase D(PLD),andβ-ketoacyl-CoA synthase(KCS),exhibited an increase followed by a subsequent decline.The activity of LOX during early shelf life(0–7 d)and the KCS activity during middle to late shelf life(14–21 d)were significantly suppressed by 1-MCP.Additionally,1-MCP effectively maintained firmness,total soluble solid(TSS)and titratable acid(TA)contents,peroxidase(POD),and phenylalanine ammonia-lyase(PAL)activities while inhibiting vitamin C degradation and weight loss.Furthermore,it restrained polyphenol oxidase(PPO)activity,ethylene production,and respiration rate increase.These findings demonstrate that 1-MCP not only delays the onset of peel greasiness but also preserves the overall storage quality of‘Yuluxiang’pear at a temperature of 20℃.This study presents a novel approach for developing new preservatives to inhibit pear fruit peel greasiness and provides a theoretical foundation for further research on pear fruit preservation.
基金supported by the China Agriculture Research System of MOF and MARA。
文摘As a cell proliferation regulator involved in wide biological processes in plants,GRF-INTERACTING FACTOR(GIF)controls different tissues development.However,whether GIF participates in fruit development remains unclear.According to transcriptome data,we identified PbGIF1was highly expressed during fruit development in cytokinins induced parthenocarpy pear.In the present study,the biofunction of PbGIF1 was initially verified.Overexpression of PbGIF1 promoted fruit size of transgenic tomato.The size of flesh fruit was not affected by cell expansion but the cell proliferation was promoted by overexpressing Pb GIF1.The accelerated cell proliferation process was also observed in PbGIF1-overexpressed transgenic pear fruit calli.The transcriptional regulation of cytokinins on PbGIF1 was further confirmed by exogenous CPPU treatments in pear fruitlets.To investigate the underlying mechanism,the cytokinins-responded factor,PbRR1,was further focused on.The results of Yeast-one-hybrid assay suggested that PbRR1 can bind to the promoter sequence of PbGIF1.The transcriptional activation of PbRR1 on PbGIF1 was also confirmed by Dual-Luciferase assays.Taken together,the results showed that cytokinins control pear fruit development via the transcriptional activation of PbGIF1 by PbRR1.
基金supported by grants from the China Agriculture Research System(CARS-28-14)the Technical System of Fruit Industry in Anhui Province,China(AHCYTX-10)the Scientific Research Projects for Postgraduates of Anhui Universities,China(YJS20210207).
文摘Drought stress is a devastating natural disaster driven by the continuing intensification of global warming,which seriously threatens the productivity and quality of several horticultural crops,including pear.Gibberellins(GAs)play crucial roles in plant growth,development,and responses to drought stress.Previous studies have shown significant reductions of GA levels in plants under drought stress;however,our understanding of the intrinsic regulation mechanisms of GA-mediated drought stress in pear remains very limited.Here,we show that drought stress can impair the accumulation of bioactive GAs(BGAs),and subsequently identified PbrGA2ox1 as a chloroplast-localized GA deactivation gene.This gene was significantly induced by drought stress and abscisic acid(ABA)treatment,but was suppressed by GA_(3)treatment.PbrGA2ox1-overexpressing transgenic tobacco plants(Nicotiana benthamiana)exhibited enhanced tolerance to dehydration and drought stresses,whereas knock-down of PbrGA2ox1 in pear(Pyrus betulaefolia)by virus-induced gene silencing led to elevated drought sensitivity.Transgenic plants were hypersensitive to ABA,and had a lower BGAs content,enhanced reactive oxygen species(ROS)scavenging ability,and augmented ABA accumulation and signaling under drought stress compared to wild-type plants.However,the opposite effects were observed with PbrGA2ox1 silencing in pear.Moreover,exogenous GA_(3)treatment aggravated the ROS toxic effect and restrained ABA synthesis and signaling,resulting in the compromised drought tolerance of pear.In summary,our results shed light on the mechanism by which BGAs are eliminated in pear leaves under drought stress,providing further insights into the mechanism regulating the effects of GA on the drought tolerance of plants.