Rhodomyrtus tomentosa is an important f leshy-fruited tree and a well-known medicinal plant of the Myrtaceae family that is widely cultivated in tropical and subtropical areas of the world.However,studies on the evolu...Rhodomyrtus tomentosa is an important f leshy-fruited tree and a well-known medicinal plant of the Myrtaceae family that is widely cultivated in tropical and subtropical areas of the world.However,studies on the evolution and genomic breeding of R.tomentosa were hindered by the lack of a reference genome.Here,we presented a chromosome-level gap-free T2T genome assembly of R.tomentosa using PacBio and ONT long read sequencing.We assembled the genome with size of 470.35 Mb and contig N50 of∼43.80 Mb with 11 pseudochromosomes.A total of 33382 genes and 239.31 Mb of repetitive sequences were annotated in this genome.Phylogenetic analysis elucidated the independent evolution of R.tomentosa starting from 14.37MYA and shared a recent WGD event with other Myrtaceae species.We identified four major compounds of anthocyanins and their synthetic pathways in R.tomentosa.Comparative genomic and gene expression analysis suggested the coloring and high anthocyanin accumulation in R.tomentosa tends to be determined by the activation of anthocyanin synthesis pathway.The positive selection and up-regulation of MYB transcription factors were the implicit factors in this process.The copy number increase of downstream anthocyanin transport-related OMT and GST gene were also detected in R.tomentosa.Expression analysis and pathway identification enriched the importance of starch degradation,response to stimuli,effect of hormones,and cell wall metabolism during the f leshy fruit development in Myrtaceae.Our genome assembly provided a foundation for investigating the origins and differentiation of Myrtaceae species and accelerated the genetic improvement of R.tomentosa.展开更多
Cadmium(Cd)accumulation in rice grain is of health concern.Identifying genes involved in grain Cd accumulation and performing molecular breeding may reduce it.In this study,knockout of OsNRAMP2,a member of the NRAMP f...Cadmium(Cd)accumulation in rice grain is of health concern.Identifying genes involved in grain Cd accumulation and performing molecular breeding may reduce it.In this study,knockout of OsNRAMP2,a member of the NRAMP family,reduced grain Cd concentrations by more than 38%,and overexpressing OsNRAMP2 increased grain Cd concentrations by more than 50%.Physiological experiments showed that OsNRAMP2 facilitated Cd translocation from root to shoot by positively regulating Cd efflux from the vacuoles.At filling stage,OsNRAMP2 was highly expressed in all tissues except for husk,suggesting its role in Cd remobilization.Changes in OsNRAMP2 expression affected the concentrations of Fe,Mn,Zn,and Cu in grain and also affected rice growth.Phylogenetic analysis showed that the distribution of OsNRAMP2 haplotypes between japonica and indica was different.Among the four haplotypes of OsNRAMP2,Hap 1,with a 6-bp nucleotide insertion in exon 1,had grain Cd concentration at least 45.3%lower than any of the other three haplotypes.Almost all(99.3%)japonica accessions but rare indica accessions(4.44%)from the 3K sequenced rice genomes carry Hap 1 of OsNRAMP2.Our study sheds light on the molecular mechanism of grain Cd accumulation and provides a promising target for low-Cd rice breeding.展开更多
Leaf rolling and discoloration are two chilling-injury symptoms that are widely used as indicators for the evaluation of cold tolerance at the seedling stage in rice. However, the difference in cold-response mechanism...Leaf rolling and discoloration are two chilling-injury symptoms that are widely used as indicators for the evaluation of cold tolerance at the seedling stage in rice. However, the difference in cold-response mechanisms underlying these two traits remains unknown. In the present study, a cold-tolerant rice cultivar, Lijiangxintuanheigu, and a cold-sensitive cultivar, Sanhuangzhan-2, were subjected to low-temperature treatments and physiolog-ical and genome-wide gene expression analyses were conducted. Leaf rolling occurred at temperatures lower than 11℃, whereas discoloration appeared at moderately low temperatures such as 13℃. Chlorophyll contents in both cultivars were significantly decreased at 13℃, but not altered at 11℃. In contrast, the relative water content and relative electrolyte leakage of both cultivars decreased significantly at 11℃, but did not change at 13℃. Expression of genes associated with calcium signaling and abscisic acid (ABA) degradation was significantly altered at 11℃ in comparison with 25℃ and 13℃. Numerous genes in the DREB, MYB, bZIP, NAC, Zinc finger, bHLH, and WRKY gene families were differentially expressed. Many aquaporin genes and the key genes in trehalose and starch synthesis were down regulated at 11℃ in comparison with 25℃ and 13℃. These results suggest that the two chilling injury symptoms are temperature-specific and are controlled by different mechanisms. Cold-induced leaf rolling is associated with calcium and ABA signaling pathways and is regulated by multiple transcriptional regulators. The suppression of aquaporin genes and reduced accumulation of soluble sugars under cold stress results in a reduction in cellular water potential and consequently leaf rolling.展开更多
The inessential heavy metal/loids cadmium(Cd)and arsenic(As),which often co-occur in polluted paddy soils,are toxic to rice.Silicon(Si)treatment is known to reduce Cd and As toxicity in rice plants.To better understan...The inessential heavy metal/loids cadmium(Cd)and arsenic(As),which often co-occur in polluted paddy soils,are toxic to rice.Silicon(Si)treatment is known to reduce Cd and As toxicity in rice plants.To better understand the shared mechanisms by which Si alleviates Cd and As stress,rice seedlings were hydroponically exposed to Cd or As,then treated with Si.The addition of Si significantly ameliorated the inhibitory effects of Cd and As on rice seedling growth.Si supplementation decreased Cd and As translocation from roots to shoots,and significantly reduced Cd-and As-induced reactive oxygen species generation in rice seedlings.Transcriptomics analyses were conducted to elucidate molecular mechanisms underlying the Si-mediated response to Cd or As stress in rice.The expression patterns of the differentially expressed genes in Cd-or As-stressed rice roots with and without Si application were compared.The transcriptomes of the Cd-and As-stressed rice roots were similarly and profoundly reshaped by Si application,suggesting that Si may play a fundamental,active role in plant defense against heavy metal/loid stresses by modulating whole genome expression.We also identified two novel genes,0s01g0524500 and 0s06g0514800,encoding a myeloblastosis(MYB)transcription factor and a thionin,respectively,which may be candidate targets for Si to alleviate Cd and As stress in rice,as well as for the generation of Cd-and/or As-resistant plants.This study provides valuable resources for further clarification of the shared molecular mechanisms underlying the Si-mediated alleviation of Cd and As toxicity in rice.展开更多
Silicon(Si)has been shown to alleviate Cd stress in rice.Here,we investigated the beneficial effects of foliar Si in an indica rice Huanghuazhan(HHZ).Our results showed that foliar Si in-creases the dry weight and dec...Silicon(Si)has been shown to alleviate Cd stress in rice.Here,we investigated the beneficial effects of foliar Si in an indica rice Huanghuazhan(HHZ).Our results showed that foliar Si in-creases the dry weight and decreases Cd translocation in Cd-exposed rice at the grain-filling stage only,implying that the filling stage is critical for foliar Si to reduce Cd accumulation.We also investigated the transcriptomics in flag leaves(FLs),spikelets(SPs),and node Is(NIs)of Cd-exposed HHZ after foliar Si application at the filling stage.Importantly,the gene expression profiles associated with the Si-mediated alleviation of Cd stress were tissue spe-cific,while shared pathways were mediated by Si in Cd-exposed rice tissues.Furthermore,after the Si treatment of Cd-exposed rice,the ATP-binding cassette(ABC)-transporters were mostly upregulated in FL and SP,while the bivalent cation transporters were mostly down-regulated in FL and NI,possibly helping to reduce Cd accumulation.The genes associated with essential nutrient transporters,carbohydrate and secondary metabolite biosynthesis,and cytochrome oxidase activity were mostly upregulated in Cd-exposed FL and SP,which may help to alleviate oxidative stress and improve plant growth under Cd exposure.Inter-estingly,genes responsible for signal transduction were negatively regulated in FL,but pos-itively regulated in SP,by foliar Si.Our results provide transcriptomic evidence that foliar Si plays an active role in alleviating the effects of Cd exposure in rice.In particular,foliar Si may alter the expression pattern of genes associated with transport,biosynthesis and metabolism,and oxidation reduction.展开更多
基金supported by the Natural Science Foundation of Crops Research Institute and Guangdong Academy of Agricultural(0145)the Scientific Innovation Strategy-Construction of High-Level Academy of Agriculture Science(R2019PY-JX003)Research and Development Program in Key Areas of the Guangdong Province(2021B0707010010)。
文摘Rhodomyrtus tomentosa is an important f leshy-fruited tree and a well-known medicinal plant of the Myrtaceae family that is widely cultivated in tropical and subtropical areas of the world.However,studies on the evolution and genomic breeding of R.tomentosa were hindered by the lack of a reference genome.Here,we presented a chromosome-level gap-free T2T genome assembly of R.tomentosa using PacBio and ONT long read sequencing.We assembled the genome with size of 470.35 Mb and contig N50 of∼43.80 Mb with 11 pseudochromosomes.A total of 33382 genes and 239.31 Mb of repetitive sequences were annotated in this genome.Phylogenetic analysis elucidated the independent evolution of R.tomentosa starting from 14.37MYA and shared a recent WGD event with other Myrtaceae species.We identified four major compounds of anthocyanins and their synthetic pathways in R.tomentosa.Comparative genomic and gene expression analysis suggested the coloring and high anthocyanin accumulation in R.tomentosa tends to be determined by the activation of anthocyanin synthesis pathway.The positive selection and up-regulation of MYB transcription factors were the implicit factors in this process.The copy number increase of downstream anthocyanin transport-related OMT and GST gene were also detected in R.tomentosa.Expression analysis and pathway identification enriched the importance of starch degradation,response to stimuli,effect of hormones,and cell wall metabolism during the f leshy fruit development in Myrtaceae.Our genome assembly provided a foundation for investigating the origins and differentiation of Myrtaceae species and accelerated the genetic improvement of R.tomentosa.
基金supported by the National Natural Science Foundation of China(31901488)the Guangdong Basic and Applied Basic Research Foundation(2020A1515010193)+3 种基金the Innovation Team Project of Guangdong Modern Agricultural Industrial System(2021KJ106,2022KJ106)the Scientific and Technological Plan of Guangzhou(201804020078,202102021005)the Special fund for scientific innovation strategy-construction of high level Academy of Agriculture Science(R2021PY-QF002,202027,R2019-JX001,R2021PY-QF001)the Guangdong Key Laboratory of New Technology in Rice Breeding(2020B1212060047).
文摘Cadmium(Cd)accumulation in rice grain is of health concern.Identifying genes involved in grain Cd accumulation and performing molecular breeding may reduce it.In this study,knockout of OsNRAMP2,a member of the NRAMP family,reduced grain Cd concentrations by more than 38%,and overexpressing OsNRAMP2 increased grain Cd concentrations by more than 50%.Physiological experiments showed that OsNRAMP2 facilitated Cd translocation from root to shoot by positively regulating Cd efflux from the vacuoles.At filling stage,OsNRAMP2 was highly expressed in all tissues except for husk,suggesting its role in Cd remobilization.Changes in OsNRAMP2 expression affected the concentrations of Fe,Mn,Zn,and Cu in grain and also affected rice growth.Phylogenetic analysis showed that the distribution of OsNRAMP2 haplotypes between japonica and indica was different.Among the four haplotypes of OsNRAMP2,Hap 1,with a 6-bp nucleotide insertion in exon 1,had grain Cd concentration at least 45.3%lower than any of the other three haplotypes.Almost all(99.3%)japonica accessions but rare indica accessions(4.44%)from the 3K sequenced rice genomes carry Hap 1 of OsNRAMP2.Our study sheds light on the molecular mechanism of grain Cd accumulation and provides a promising target for low-Cd rice breeding.
基金supported in part by the Ph.D. Start-up Fund of Natural Science Foundation of Guangdong Province, China (2015A030310419)the Guangdong Scientific and Technological Plan (2015B020231002, 2017A070702006, 2017A020208022)+3 种基金the Guangzhou Scientific and Technological Plan (201804020078)the Guangdong-Hong Kong joint project (2017A050506035)the Development Project of Guangdong Provincial Key Lab (2017B030314173)the Special Fund of Central Government Guided Local Scientific Development
文摘Leaf rolling and discoloration are two chilling-injury symptoms that are widely used as indicators for the evaluation of cold tolerance at the seedling stage in rice. However, the difference in cold-response mechanisms underlying these two traits remains unknown. In the present study, a cold-tolerant rice cultivar, Lijiangxintuanheigu, and a cold-sensitive cultivar, Sanhuangzhan-2, were subjected to low-temperature treatments and physiolog-ical and genome-wide gene expression analyses were conducted. Leaf rolling occurred at temperatures lower than 11℃, whereas discoloration appeared at moderately low temperatures such as 13℃. Chlorophyll contents in both cultivars were significantly decreased at 13℃, but not altered at 11℃. In contrast, the relative water content and relative electrolyte leakage of both cultivars decreased significantly at 11℃, but did not change at 13℃. Expression of genes associated with calcium signaling and abscisic acid (ABA) degradation was significantly altered at 11℃ in comparison with 25℃ and 13℃. Numerous genes in the DREB, MYB, bZIP, NAC, Zinc finger, bHLH, and WRKY gene families were differentially expressed. Many aquaporin genes and the key genes in trehalose and starch synthesis were down regulated at 11℃ in comparison with 25℃ and 13℃. These results suggest that the two chilling injury symptoms are temperature-specific and are controlled by different mechanisms. Cold-induced leaf rolling is associated with calcium and ABA signaling pathways and is regulated by multiple transcriptional regulators. The suppression of aquaporin genes and reduced accumulation of soluble sugars under cold stress results in a reduction in cellular water potential and consequently leaf rolling.
基金supported by the National Natural Science Foundation of China(No.41877143)the National Key Research and Development Project of China(No.2016YFD0800700)the Science and Technology Planning Project of Guangdong Province(Nos.2015B020237008 and 2015B020207001).
文摘The inessential heavy metal/loids cadmium(Cd)and arsenic(As),which often co-occur in polluted paddy soils,are toxic to rice.Silicon(Si)treatment is known to reduce Cd and As toxicity in rice plants.To better understand the shared mechanisms by which Si alleviates Cd and As stress,rice seedlings were hydroponically exposed to Cd or As,then treated with Si.The addition of Si significantly ameliorated the inhibitory effects of Cd and As on rice seedling growth.Si supplementation decreased Cd and As translocation from roots to shoots,and significantly reduced Cd-and As-induced reactive oxygen species generation in rice seedlings.Transcriptomics analyses were conducted to elucidate molecular mechanisms underlying the Si-mediated response to Cd or As stress in rice.The expression patterns of the differentially expressed genes in Cd-or As-stressed rice roots with and without Si application were compared.The transcriptomes of the Cd-and As-stressed rice roots were similarly and profoundly reshaped by Si application,suggesting that Si may play a fundamental,active role in plant defense against heavy metal/loid stresses by modulating whole genome expression.We also identified two novel genes,0s01g0524500 and 0s06g0514800,encoding a myeloblastosis(MYB)transcription factor and a thionin,respectively,which may be candidate targets for Si to alleviate Cd and As stress in rice,as well as for the generation of Cd-and/or As-resistant plants.This study provides valuable resources for further clarification of the shared molecular mechanisms underlying the Si-mediated alleviation of Cd and As toxicity in rice.
基金This work was financially supported by the National Key Research and Development Project of China(No.2016YFD0800700)the National Natural Science Foundation of China(No.41877143)+2 种基金the Science and Technology Planning Project of Guangdong Province,China(No.2015B020237008)the Guangdong Basic and Applied Basic Research Foundation(No.2020A1515010906)the Special Rural Revitalization Funds of Guangdong Province(No.2021KJ382).
文摘Silicon(Si)has been shown to alleviate Cd stress in rice.Here,we investigated the beneficial effects of foliar Si in an indica rice Huanghuazhan(HHZ).Our results showed that foliar Si in-creases the dry weight and decreases Cd translocation in Cd-exposed rice at the grain-filling stage only,implying that the filling stage is critical for foliar Si to reduce Cd accumulation.We also investigated the transcriptomics in flag leaves(FLs),spikelets(SPs),and node Is(NIs)of Cd-exposed HHZ after foliar Si application at the filling stage.Importantly,the gene expression profiles associated with the Si-mediated alleviation of Cd stress were tissue spe-cific,while shared pathways were mediated by Si in Cd-exposed rice tissues.Furthermore,after the Si treatment of Cd-exposed rice,the ATP-binding cassette(ABC)-transporters were mostly upregulated in FL and SP,while the bivalent cation transporters were mostly down-regulated in FL and NI,possibly helping to reduce Cd accumulation.The genes associated with essential nutrient transporters,carbohydrate and secondary metabolite biosynthesis,and cytochrome oxidase activity were mostly upregulated in Cd-exposed FL and SP,which may help to alleviate oxidative stress and improve plant growth under Cd exposure.Inter-estingly,genes responsible for signal transduction were negatively regulated in FL,but pos-itively regulated in SP,by foliar Si.Our results provide transcriptomic evidence that foliar Si plays an active role in alleviating the effects of Cd exposure in rice.In particular,foliar Si may alter the expression pattern of genes associated with transport,biosynthesis and metabolism,and oxidation reduction.