Application of virus-free sweetpotato is a breakthrough of sweetpotato production. Several popular varieties were adopted to study their yield increase potential and their use in breeding in this research. The results...Application of virus-free sweetpotato is a breakthrough of sweetpotato production. Several popular varieties were adopted to study their yield increase potential and their use in breeding in this research. The results showed that after virus-elimination, all varieties had a yield increase ranging from 14.95% - 91. 61% and marketable quality improvement, despite the changes in location and season. The changes of dry matter content and disease resistance were not significant. Virus-free sweetpotato performed vigorous vine growth and strong dry matter assimilation ability. Virus-free parents had a slightly high seed setting percentage, but its flowering ability and performance of off-springs were similar to that of its check plants.展开更多
This study was to develop the real-time fluorescence quantitative PCR technique for detecting the ratoon stunting disease (RSD) in virus-free seedcane seedlings. Healthy tissue culture seedlings were obtained from s...This study was to develop the real-time fluorescence quantitative PCR technique for detecting the ratoon stunting disease (RSD) in virus-free seedcane seedlings. Healthy tissue culture seedlings were obtained from six plants of sugarcane ROC22, which had been confirmed RSD-positive by detecting the sugarcane juice, by employing the sugarcane seedlings production protocol. Real-time fluorescence quantitative PCR was used to detect RSD pathogens in tissue culture sam- pies. The results showed that target fragment of RSD pathogens was not found in all 10 samples in real-time fluorescence quantitative PCR, with the Ct values of 37 - 39. The healthy tissue culture sugarcane seedlings do not carry RSD pathogens, indicating that adopting healthy seedcane seedlings production technique could thoroughly get rid of RSD pathogens.展开更多
[ Objective] This study aimed to investigate the tissue culture and rapid propagation techniques of Benihoppe strawberry. [ Method] Shoot tips of new stolons of Benihoppe strawberry were used as experimental materials...[ Objective] This study aimed to investigate the tissue culture and rapid propagation techniques of Benihoppe strawberry. [ Method] Shoot tips of new stolons of Benihoppe strawberry were used as experimental materials to analyze the effects of media type, cytokinin type and concentration, carbon source type and concentration, and light intensity on tissue culture and propagation of Benihoppe strawberry. [ Result] MS was the optimal media for plantlet propagation. In the media containing 1.2 ing/L BA (with addition of 0.1 mg/L NAA), fresh weight, dry weight and propagation coefficient of strawberry plantlets reached the maxi- mum, which were 2.259 g, 0. 221 g and 12.4, respectively. The optimal carbon source was 30 g/L sucrose, and the optimal light intensity was 1 600 lx. [ Conclu- sion] The best media for tissue culture and rapid propagation of Benihoppe strawberry was MS + BA 1.2 mg/L + NAA 0. 1 mg/L + sucrose 30 g/L + agar 8 g/L. This study provided scientific basis for large-scale production of Benihoppe strawberry.展开更多
Virus-free sugarcane seedlings have improved biomass and sucrose content compared with ordinary seedlings, and sucrose invertases are key enzymes regulating sugarcane growth and sucrose accumulation. In this study, th...Virus-free sugarcane seedlings have improved biomass and sucrose content compared with ordinary seedlings, and sucrose invertases are key enzymes regulating sugarcane growth and sucrose accumulation. In this study, the differences in the expression levels of 3 invertase genes, CWI, SAI and NI, between virus- free and ordinary sugarcane seedlings were analyzed. Compared with ordinary sugarcane plants, the expression of CWI was mainly up-regulated in immature leaves and stems at elongation stage and leaves and immature internodes at maturation stage, and especially, greatly up-regulated in immature interuedes at maturation stage of virus-free plants. The expression of SAI and NI were mainly up-regnlated in leaves and immature internedes of virus-free plants at maturation stage, which might be beneficial to sugar accumulation and rapid utilization of monosaccharide in the stalks of virus-free plants. It is further indicated that virus-free treatment could significantly improve the expression of sucrose invertases at late growth period, and might facilitate the increase of plant biomass.展开更多
It is the simplest,fastest and effective way to improve the yield level of potato by selecting high quality virus-free seed potato for field production and maintaining the original characters of virus-free minituber. ...It is the simplest,fastest and effective way to improve the yield level of potato by selecting high quality virus-free seed potato for field production and maintaining the original characters of virus-free minituber. Microtuber is featured by small volume,no pathogen,convenient storage and transportation,which can be induced in summer with high temperature and humidity,and overcome a series of problems such as poor survival rate of transplanted test-tube plantlets,and easy pollution of cutting tips. Therefore,it can replace conventional test-tube plantlets directly for reproduction. Meantime,if minitubers are sown ahead of time using cold frame,the growth stage of potato minituber will avoid the occurrence period of aphids. The use of gauze cover for insect prevention has good effect on maintaining the excellent characters of microtuber. The yield and quality of virus-free potato are greatly improved by means of virus-free culture of shoot tip seedlings,subculture propagation of virus-free seedlings,induction of microtubers by dark culture,cultivation of breeder’s seeds in greenhouse and screenhouse to preserve the characters of potato.展开更多
At the end of potato plants vegetation virus in-fection induced both decrease in maximum amplitude of delayed fluorescence maximal amplitude and increase half time of its decrease, as well as reduction in the amount o...At the end of potato plants vegetation virus in-fection induced both decrease in maximum amplitude of delayed fluorescence maximal amplitude and increase half time of its decrease, as well as reduction in the amount of stems, plants’ height and assimilation area surface, yield, acceleration of plants development and their early die-off. The differences of DF pa-rameters and yields between strongly and weakly infected plants increase in case of a combined virus infection. In industrial test of the selection of virus-free planting potato by the use of DF parameter, a rise in the yield and de-crease degree of viral infection of crops was obtained.展开更多
In flowering plants,the inflorescence meristem(IM)provides founder cells to form successive floral meristems,which are precursors of fruits and seeds.The activity and developmental progression of IM are thus critical ...In flowering plants,the inflorescence meristem(IM)provides founder cells to form successive floral meristems,which are precursors of fruits and seeds.The activity and developmental progression of IM are thus critical for yield production in seed crops.In some cereals,such as rice(Oryza sativa)and maize(Zea mays),the size of undifferentiated IM,which is located at the inflorescence apex,is positively associated with yield traits such as spikelet number.However,the relationship between IM size and yieldrelated spike traits remains unknown in the Triticeae tribe.Here we report that IM size has a negative correlation with yield traits in barley(Hordeum vulgare).Three FASCIATED EAR(FEA)orthologs,HvFEA2,HvFEA3,and HvFEA4,regulate IM size and spike morphogenesis and ultimately affect yield traits.Three HvFEAs genes are highly expressed in developing spikes,and all three loss-of-function mutants exhibit enlarged IM size,shortened spikes,and reduced spikelet number,which may lead to reduced grain yield.Natural variations identified in HvFEAs indicate selection events during barley domestication.We further reveal that HvFEA4,as a transcription factor,potentially targets multiple pathways during reproductive development,including transcriptional control,phytohormone signaling,and redox status.The roles of barley FEA genes in limiting IM size and promoting spikelet formation suggest the potential of increasing yield by manipulating IM activity.展开更多
Chrysanthemum morifolium,an ornamental crop with diverse forms of inflorescence,is a good model for studying flower development in Asteraceae.However,the genetic background is complex and the mechanisms of regulating ...Chrysanthemum morifolium,an ornamental crop with diverse forms of inflorescence,is a good model for studying flower development in Asteraceae.However,the genetic background is complex and the mechanisms of regulating flower development are still unclear.Here,we identified two natural mutant lines of chrysanthemum and named them M1 and M2 according to the severity of the phenotype.Both lines showed defects in petal identity,and the petals of the M1 line had a mild phenotype:partially loss of petal identity and conversion of petals into green,leaf-like organs.The M2 line had severe phenotypes:in addition to severe petal defects,secondary inflorescences were produced in the capitulum to replace the normal ray and disc florets,which indicated a transformation of a flower meristem into an inflorescence meristem.Transcriptome sequencing of WT and M2 inflorescences was performed and found altered expression of floral organ development A,B and E class genes,where B and E class genes were significantly down-regulated.qRT-PCR analysis in both M1 and M2 lines revealed that the expression of three chrysanthemum class B genes CmAP3.1,CmAP3.2 and CmPI,was negatively correlated with phenotypic severity.This suggests that class B genes in chrysanthemum not only have conserved functions in determining petal identity but also were involved in the determinacy of the flower meristem.This study provides insights into the functions of class B genes in flower development,and is informative for dissecting the molecular mechanisms of flower development in chrysanthemum.展开更多
THIS year's International AIDS Society Conference on HIV Pathogenesis, Treatment and Preven-/tion, held in Kuala Lumpur, Malaysia, made major headlines when Timothy Hendch, an American doctor, announced that two mor...THIS year's International AIDS Society Conference on HIV Pathogenesis, Treatment and Preven-/tion, held in Kuala Lumpur, Malaysia, made major headlines when Timothy Hendch, an American doctor, announced that two more cancer patients may have been cured of HIV after receiving bone-marrow transplants to treat lymphoma. Both patients had been taking retroviral medication, and continued to do so after the transplants as their viral levels sank until doctors were unable to find any traces of HIV in the patients' blood.展开更多
Although AGAMOUS-LIKE6 (AGL6) MADS-box genes are ancient with wide distributions in gymnosperms and angiosperms, their functions remain poorly understood. Here, we show the biological role of the AGL6-1ike gene, OsMAD...Although AGAMOUS-LIKE6 (AGL6) MADS-box genes are ancient with wide distributions in gymnosperms and angiosperms, their functions remain poorly understood. Here, we show the biological role of the AGL6-1ike gene, OsMADS6, in specifying floral organ and meristem identities in rice (Oryza sativa L.). OsMADS6 was strongly ex- pressed in the floral meristem at early stages. Subsequently, OsMADS6 transcripts were mainly detectable in paleas, lodicules, carpels and the integument of ovule, as well as in the receptacle. Compared to wild type plants, osmads6 mutants displayed altered palea identity, extra glume-like or mosaic organs, abnormal carpel development and loss of floral meristem determinacy. Strikingly, mutation of a SEPALLATA (SEP)-like gene, OsMADS1 (LHS1), enhanced the defect of osmads6 flowers, and no inner floral organs or glume-like structures were observed in whorls 2 and 3 of osmadsl-z osmads6-1 flowers. Furthermore, the osmadsl-z osmads6-1 double mutants developed severely indetermi- nate floral meristems. Our finding, therefore, suggests that the ancient OsMADS6 gene is able to specify "floral state" by determining floral organ and meristem identities in monocot crop rice together with OsMADS1.展开更多
It is vital to determine the effective photoperiods of maize for making full use of tropical germplasm, which is the foundation for determining the effect of latitude and planting date on the development of photoperio...It is vital to determine the effective photoperiods of maize for making full use of tropical germplasm, which is the foundation for determining the effect of latitude and planting date on the development of photoperiod-sensitive maize cultivars. The objective of this study is to determine the photoperiod-sensitive inductive phase using reciprocal transfer between long- day (LD) (15 h d^-1) and short-day conditions (SD) (9 h d^-1). For Huangzao 4 and CML288, days to tassel and pollen shedding were recorded, and stem apical meristems (SAM) were observed by a laser scanning confocal microscope. The results show that the seedlings are insensitive to photoperiod when they are very young (juvenile). However, after this period, LD delays flowering and increases the leaf numbers below the inflorescence, and the length of the interval of the photoperiod-sensitive inductive phase is longer under LD conditions than under SD conditions. Transferred from SD to LD, plants show a sudden decrease in leaf numbers once sufficient SD has been received for flower commitment. While transferred from LD to SD, plants have a continuous increase in leaf numbers during the photoperiod sensitive inductive phase under LD conditions. At the same time, when plants are competent to flowers, the obvious morphology is the elongation of maize SAM. There is an obvious variance of the photoperiod sensitive phase under LD and SD conditions in different maize.展开更多
Background:Manual topping is a routine agronomic practice for balancing the vegetative and reproductive growth of cotton(Gossypium hirsutum)in China,but its cost-effectiveness has decreased over time.Therefore,there i...Background:Manual topping is a routine agronomic practice for balancing the vegetative and reproductive growth of cotton(Gossypium hirsutum)in China,but its cost-effectiveness has decreased over time.Therefore,there is an urgent need to replace manual topping with new approaches,such as biological topping.In this study,we examined the function of Gh REV transcription factors(a classⅢhomeodomain-leucine zipper family,HD-ZIPⅢ)in regulating the development of shoot apical meristem(SAM)in cotton with the purpose of providing candidate genes for biological topping of cotton in the future.Results:We cloned four orthologous genes of At REV in cotton,namely Gh REV1,Gh REV2,Gh REV3,and Gh REV4.All the Gh REVs expressed in roots,stem,leaves,and SAM.Compared with Gh REV1 and Gh REV3,the expression level of Gh REV2 and Gh REV4 was higher in the SAM.However,only Gh REV2 had transcriptional activity.Gh REV2 is localized in the nucleus;and silencing it via virus-induced gene silencing(VIGS)produced an abnormal SAM.Two key genes,Gh WUSA10 and Gh STM,which involved in regulating the development of plant SAM,showed about 50%reduction in their transcripts in VIGS-Gh REV2 plants.Conclusion:Gh REV2 positively regulates the development of cotton SAM by regulating Gh WUSA10 and Gh STM potentially.展开更多
In wheat plants at the vegetative growth stage, the shoot apical meristem (SAM) produces leaf primordia. When reproductive growth is initiated, the SAM forms an inflorescence meristem (IM) that differentiates a series...In wheat plants at the vegetative growth stage, the shoot apical meristem (SAM) produces leaf primordia. When reproductive growth is initiated, the SAM forms an inflorescence meristem (IM) that differentiates a series of spikelet meristem (SM) as the branch. The SM then produces a series of floret meristem (FM) as the branch. To identify the mechanisms that regulate formation of the reproductive meristems in wheat, we have investigated a leaf initiation mutant, fushi-darake (fdk) which was developed by ion beam mutagenesis. The morphological traits were compared in wild type (WT) and fdk mutant plants grown in the experimental field. WT plants initiated leaves from SAM at regular intervals in spiral phyllotaxy, while fdk plants had 1/2 alternate phyllotaxy with rapid leaf emergence. The fdk plants have increased numbers of nodes and leaves compared with WT plants. The time interval between successive leaf initiation events (plastochron) was measured in plants grown in a growth chamber. The fdk plants clearly show the rapid leaf emergence, indicating a shortened plastochron. Each tiller in fdk plants branches at the upper part of the culm. The fine structure of organ formation in meristems of fdk plants was examined by scanning electron microscopy (SEM). The SEM analysis indicated that fdk plants show transformation of spikelet meristems into vegetative shoot meristems. In conclusion, the fdk mutant has a heterochronic nature, i.e., both reproductive and vegetative programs were simultaneously in operation during the reproductive phase, resulting in a shortened plastochron and transformation of reproductive spikelets into vegetative shoots.展开更多
To further study the floral organogenesis and discussing the floral origin of Phytolacca, the procedures of floral organogenesis were observed in Phytolacca esculenta and Phytolacca zhejiangensis. The results showed t...To further study the floral organogenesis and discussing the floral origin of Phytolacca, the procedures of floral organogenesis were observed in Phytolacca esculenta and Phytolacca zhejiangensis. The results showed that the floral organogenesis was consistent in Phytolacca. Their sepals were 2/5 helix, and with counter-clockwise and clockwise, usually the first sepal located at non-median of abaxial side. The first sepal of Phytolacca esculenta was initiated at non-median of adaxial side. There was no evident relationship between sepal and stamen initiating position, and the stamens initiated on ring meristem, they initiated approximately at the same time, and when the androecium member was numerous, they initiated centrifugally, the outer stamen initiated irregularly. Carpel initiated alternately with inner stamens. And the carpels connected by septum, if the septum grew more, the carpel was syncarpous at morphology, otherwise the carpel was apocarpous at morphology. So the syncarpous and the apocarpous have no successively relationship on evolution. Ovule initiated inside the carpel and opposite to carpel. Androecium, carpel and ovule initiated at ring meristem.展开更多
Different aspects of micropropagation through meristem culture for the production of virus indexed source plants, <i><span style="font-family:Verdana;">in vitro</span></i><span sty...Different aspects of micropropagation through meristem culture for the production of virus indexed source plants, <i><span style="font-family:Verdana;">in vitro</span></i><span style="font-family:Verdana;"> tuberization and field evaluation of the </span><i><span style="font-family:Verdana;">in vitro</span></i><span style="font-family:Verdana;"> regenerated plants were studied on four commercial cultivars of potato (</span><i><span style="font-family:Verdana;">Solanum tuberosum</span></i><span style="font-family:Verdana;"> L.) viz., Diamant, Cardinal, Shilbilati and Lalpakri. The investigation was conducted at Rajshahi, Bangladesh from December 2010 to March 2012 to produce virus-free potato plantlets through meristem culture, shoot multiplications with root induction as well as their acclimatization and evaluation of morphological characters and tuber yield under field condition. Shoot tips of 25</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">30 day old field</span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""><span style="font-family:Verdana;">grown plants of above mentioned four cultivars were used for meristem isolation. After isolation, meristems of these varieties of potato were cultured on “M” shaped filter paper bridge in Murashige and Skoog (MS) liquid medium. Four different treatments of media formulations viz. 0.1 mg/L KIN + 0.1 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">, 0.1</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">mg/L KIN + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">, 0.5 mg/L KIN + 0.1 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> and 0.5 mg/L KI</span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">N + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> were used as plant growth regulators. From these formulations MS + 0.1 mg/L KIN + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> was found to be the best for </span></span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">primary establishment of meristem culture. The primar</span><span style="font-family:Verdana;">ily</span><span style="font-family:Verdana;"> established meristems were subcultured on to MS semisolid basal medium supplemented with four different treatment combinations of hormones viz. 0.5 mg/L BA</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">+ 1.0 mg/L IBA;0.1 mg/L KIN + 0.1 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">;0.5 mg/L BA + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> and 0.5 mg/L KIN + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> were used to identify the suitable media compositions for shoot proliferation. Results showed that out of these four media treatments the formulation 0.5 mg/L BA + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> was found to be the best suitable for shoot generation. Among the four cultivars of potato higher frequency of shoot proliferation (number of shoots/explant and longest shoot length) was observed in Diamant, though the highest shoot formation (76%) was recorded in Cardinal. Virus free </span><i><span style="font-family:Verdana;">in vitro</span></i><span style="font-family:Verdana;"> grown potato plantlets were ob</span><span style="font-family:Verdana;">tained through DAS-ELISA test and used substantially for m</span><span style="font-family:Verdana;">icro-propagation. After gradual acclimatization of rooted plantlets of four potato cultivars</span></span><span style="font-family:Verdana;">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> they were transferred into the field for cultivation and established successfully. It was observed from the field study of </span><i><span style="font-family:Verdana;">in vitro</span></i><span style="font-family:Verdana;"> meristem-derived plantlets that there were no virus-affected plants. The virus-free exotic varieties were much superior in all vegetative attributes and yield compare</span></span><span style="font-family:Verdana;">d</span><span style="font-family:Verdana;"> to those of indigenous varieties with producing potato plants of normal height. In contrast, the indigenous varieties took </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">longer time to tuber initiation and maturity, lower plant height and number of leaves per plant, </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">higher number of tubers but </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">lower amount of tuber weight per plant, and poorer tuber grade than the exotic varieties. However, the variety Cardinal exposed the best performances in the context of survival percentage of plantlets (90%), days to tuber initiation (DTI), </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">number of leaves per plant (NL), tuber weight per plant (343.40%) and the percentage of rich tuber grade.</span>展开更多
Shoot meristems used for the study were exercised from the in vitro regenerated shoots cultured on MS medium supplemented with 0.5 mg/L of BAP for multiplication. The sensitivity of the in vitro regenerated was studie...Shoot meristems used for the study were exercised from the in vitro regenerated shoots cultured on MS medium supplemented with 0.5 mg/L of BAP for multiplication. The sensitivity of the in vitro regenerated was studied using shoot meristems of 0.5 cm. Shoot meristems were cultured on medium containing 10-100 mg/l kanamycin to determine the concentration that was lethal for multiple shoot induction and root induction. The response of shoot multiplication decreased (66.2%-6.2%) as the concentration of kanamycin increased (10.0-70.0 mg/L) with complete inhibition of shoot proliferation at 100 mg/L kanamycin. The rooting phase was very sensitive to kanamycin compared to shoot multiplication. The percentage of shoots that rooted decreased (53.8%-4.8%) with increase in the concentration of kanamycin (10.0-70.0 mg/l) on IBA and 2,4-D supplemented medium. For transformation studies, the shoot tips that were infected with Agrobacterium strain were placed on selection medium containing MS medium with 0.5 mg/L BAP and 100 mg/L kanamycin and scored for the putative transformed shoots. An average of 62.2% of shoot tips developed shoot buds from the base and the shoots reached a length of 0.5-1.0 cm at the end of 30 days of culture on the selective medium in comparison to control which showed no response. An average of 66.7% of the regenerated plants showed GUS expression on selection medium where 43.2% and 65% of GUS expression was recorded in the leaves and callus. Leaves and callus induced from the controls did not show GUS activity. Stable integration of nptII gene with the genomic DNA from these transformed plants was confirmed through PCR analysis. Our result presents an efficient regeneration system using in vitro derived shoot meristems for Agrobacterium mediated gene transfer.展开更多
The ultrastructure of apical meristem cells was studied in Triticum aestivum L. cv. “Trizo” seedlings grown on soil without or enriched with selenium and survived 14 days’ stress caused by lead pollution in the soi...The ultrastructure of apical meristem cells was studied in Triticum aestivum L. cv. “Trizo” seedlings grown on soil without or enriched with selenium and survived 14 days’ stress caused by lead pollution in the soil. The soil treatments: control—the original soil;(Pb1)—50 mg·kg−1;(Pb2)—100 mg·kg−1;(Pb1 + Se1) —0.4 mg·kg−1 Se added to Pb1 treated soil;(Pb1 + Se2)—0.8 mg·kg−1 Se added to Pb1 treated soil;(Pb2 + Se1)—0.4 mg·kg−1 Se added to Pb2 treated soil;(Pb2 + Se2)—0.8 mg·kg−1 Se added to Pb2 treated soil were used. Light and other conditions were optimal for plant growth. A distinctive feature of the cells of the apical meristem of control plants was the absence of nuclear membranes. Proplastids were membrane vesicles 1 - 2 microns in diameter, filled with contents of varying degrees of density, from membrane vesicles containing only plastid DNA up to a fully formed structure of proplastids. In (Pb1)-plants, the amount of cytoplasmic ribosomes and proplastids in the meristematic cells was less than in the control. The structure of the forming proplastids was almost the same as that of the control plants. Signs of degradation of meristematic proplastids, such as a decrease of their diameter, observed in (Pb2)-plants. The introduction of selenium into lead contaminated soil increased the accumulation of Pb in plants, especially in the roots and apical meristem. In (Pb1 + Se1)-, (Pb1 + Se2)-, (Pb2 + Se1)-, and (Pb2 + Se2)-plants, the number of cytoplasmic ribosomes in meristematic cells increased, which indirectly indicates an increase in protein synthesis. Based on our concept about the formation (assembly) of proplastids in the cells of the apical meristem, we believe that toxic agents, such as lead, which inhibit the development of proplastids into chloroplasts in mesophyll cells, act on apical meristem cells at the stage when plastid DNA is replicated in the cytoplasm and is not yet surrounded by a plastid membrane.展开更多
Increasing tiller number is a target of high-yield rice breeding. Identification of tiller-defect mutants and their corresponding genes is helpful for clarifying the molecular mechanism of rice tillering. Summarizing ...Increasing tiller number is a target of high-yield rice breeding. Identification of tiller-defect mutants and their corresponding genes is helpful for clarifying the molecular mechanism of rice tillering. Summarizing research progress on the two processes of rice tiller formation, namely the formation and growth of axillary meristem, this paper reviews the effects of genetic factors, endogenous hormones, and exogenous environment on rice tillering, finding that multiple molecular mechanisms and signal pathways regulating rice tillering cooperate rice tillering, and discusses future research objectives and application of its regulatory mechanism. Elucidation of theis mechanism will be helpful for breeding high-yielding rice cultivars with ideal plant type via molecular design breeding.展开更多
文摘Application of virus-free sweetpotato is a breakthrough of sweetpotato production. Several popular varieties were adopted to study their yield increase potential and their use in breeding in this research. The results showed that after virus-elimination, all varieties had a yield increase ranging from 14.95% - 91. 61% and marketable quality improvement, despite the changes in location and season. The changes of dry matter content and disease resistance were not significant. Virus-free sweetpotato performed vigorous vine growth and strong dry matter assimilation ability. Virus-free parents had a slightly high seed setting percentage, but its flowering ability and performance of off-springs were similar to that of its check plants.
基金Supported by Special Funds for Basic Scientific Research of Guangxi Sugarcane Research Institute(G2009006,G2010006,G2009015)Sci-tech Research and Development Program of Guangxi Academy of Agricultural Sciences(200805)
文摘This study was to develop the real-time fluorescence quantitative PCR technique for detecting the ratoon stunting disease (RSD) in virus-free seedcane seedlings. Healthy tissue culture seedlings were obtained from six plants of sugarcane ROC22, which had been confirmed RSD-positive by detecting the sugarcane juice, by employing the sugarcane seedlings production protocol. Real-time fluorescence quantitative PCR was used to detect RSD pathogens in tissue culture sam- pies. The results showed that target fragment of RSD pathogens was not found in all 10 samples in real-time fluorescence quantitative PCR, with the Ct values of 37 - 39. The healthy tissue culture sugarcane seedlings do not carry RSD pathogens, indicating that adopting healthy seedcane seedlings production technique could thoroughly get rid of RSD pathogens.
文摘[ Objective] This study aimed to investigate the tissue culture and rapid propagation techniques of Benihoppe strawberry. [ Method] Shoot tips of new stolons of Benihoppe strawberry were used as experimental materials to analyze the effects of media type, cytokinin type and concentration, carbon source type and concentration, and light intensity on tissue culture and propagation of Benihoppe strawberry. [ Result] MS was the optimal media for plantlet propagation. In the media containing 1.2 ing/L BA (with addition of 0.1 mg/L NAA), fresh weight, dry weight and propagation coefficient of strawberry plantlets reached the maxi- mum, which were 2.259 g, 0. 221 g and 12.4, respectively. The optimal carbon source was 30 g/L sucrose, and the optimal light intensity was 1 600 lx. [ Conclu- sion] The best media for tissue culture and rapid propagation of Benihoppe strawberry was MS + BA 1.2 mg/L + NAA 0. 1 mg/L + sucrose 30 g/L + agar 8 g/L. This study provided scientific basis for large-scale production of Benihoppe strawberry.
基金Supported by"863"Program(2013AA102604-1)Natural Science Foundation of Hainan Province(20163124)+1 种基金Basal Research Fund for Central Public-interest Scientific Institute(ITBB140503)Earmarked Fund for China Agriculture Research System(CARS-20-2-5)
文摘Virus-free sugarcane seedlings have improved biomass and sucrose content compared with ordinary seedlings, and sucrose invertases are key enzymes regulating sugarcane growth and sucrose accumulation. In this study, the differences in the expression levels of 3 invertase genes, CWI, SAI and NI, between virus- free and ordinary sugarcane seedlings were analyzed. Compared with ordinary sugarcane plants, the expression of CWI was mainly up-regulated in immature leaves and stems at elongation stage and leaves and immature internodes at maturation stage, and especially, greatly up-regulated in immature interuedes at maturation stage of virus-free plants. The expression of SAI and NI were mainly up-regnlated in leaves and immature internedes of virus-free plants at maturation stage, which might be beneficial to sugar accumulation and rapid utilization of monosaccharide in the stalks of virus-free plants. It is further indicated that virus-free treatment could significantly improve the expression of sucrose invertases at late growth period, and might facilitate the increase of plant biomass.
基金Supported by Special Project of Potato Industry Research System in Shandong Province (SDAIT-14)。
文摘It is the simplest,fastest and effective way to improve the yield level of potato by selecting high quality virus-free seed potato for field production and maintaining the original characters of virus-free minituber. Microtuber is featured by small volume,no pathogen,convenient storage and transportation,which can be induced in summer with high temperature and humidity,and overcome a series of problems such as poor survival rate of transplanted test-tube plantlets,and easy pollution of cutting tips. Therefore,it can replace conventional test-tube plantlets directly for reproduction. Meantime,if minitubers are sown ahead of time using cold frame,the growth stage of potato minituber will avoid the occurrence period of aphids. The use of gauze cover for insect prevention has good effect on maintaining the excellent characters of microtuber. The yield and quality of virus-free potato are greatly improved by means of virus-free culture of shoot tip seedlings,subculture propagation of virus-free seedlings,induction of microtubers by dark culture,cultivation of breeder’s seeds in greenhouse and screenhouse to preserve the characters of potato.
文摘At the end of potato plants vegetation virus in-fection induced both decrease in maximum amplitude of delayed fluorescence maximal amplitude and increase half time of its decrease, as well as reduction in the amount of stems, plants’ height and assimilation area surface, yield, acceleration of plants development and their early die-off. The differences of DF pa-rameters and yields between strongly and weakly infected plants increase in case of a combined virus infection. In industrial test of the selection of virus-free planting potato by the use of DF parameter, a rise in the yield and de-crease degree of viral infection of crops was obtained.
基金financially supported by the Science and Research Grant of Southwest University of Science and Technology(19zx7146)the start-up grant from Nanjing Agricultural University(to Gang Li)+2 种基金the Australia–China Science and Research Fund Joint Research Centre grant(ACSRF48187)the Australian Research Council(DP170103352)the Waite Research Institute(WRI)of the University of Adelaide。
文摘In flowering plants,the inflorescence meristem(IM)provides founder cells to form successive floral meristems,which are precursors of fruits and seeds.The activity and developmental progression of IM are thus critical for yield production in seed crops.In some cereals,such as rice(Oryza sativa)and maize(Zea mays),the size of undifferentiated IM,which is located at the inflorescence apex,is positively associated with yield traits such as spikelet number.However,the relationship between IM size and yieldrelated spike traits remains unknown in the Triticeae tribe.Here we report that IM size has a negative correlation with yield traits in barley(Hordeum vulgare).Three FASCIATED EAR(FEA)orthologs,HvFEA2,HvFEA3,and HvFEA4,regulate IM size and spike morphogenesis and ultimately affect yield traits.Three HvFEAs genes are highly expressed in developing spikes,and all three loss-of-function mutants exhibit enlarged IM size,shortened spikes,and reduced spikelet number,which may lead to reduced grain yield.Natural variations identified in HvFEAs indicate selection events during barley domestication.We further reveal that HvFEA4,as a transcription factor,potentially targets multiple pathways during reproductive development,including transcriptional control,phytohormone signaling,and redox status.The roles of barley FEA genes in limiting IM size and promoting spikelet formation suggest the potential of increasing yield by manipulating IM activity.
基金financially supported by the National Natural Science Foundation of China(32171855)China Agriculture Research System(CARS-23-A18),Seed Industry Project of Jiangsu Province(JBGS[2021]020)+2 种基金the China Postdoctoral Science Foundation(2019M661870)the National Key Research and Development Program of China(2020YFD1000400)a Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Chrysanthemum morifolium,an ornamental crop with diverse forms of inflorescence,is a good model for studying flower development in Asteraceae.However,the genetic background is complex and the mechanisms of regulating flower development are still unclear.Here,we identified two natural mutant lines of chrysanthemum and named them M1 and M2 according to the severity of the phenotype.Both lines showed defects in petal identity,and the petals of the M1 line had a mild phenotype:partially loss of petal identity and conversion of petals into green,leaf-like organs.The M2 line had severe phenotypes:in addition to severe petal defects,secondary inflorescences were produced in the capitulum to replace the normal ray and disc florets,which indicated a transformation of a flower meristem into an inflorescence meristem.Transcriptome sequencing of WT and M2 inflorescences was performed and found altered expression of floral organ development A,B and E class genes,where B and E class genes were significantly down-regulated.qRT-PCR analysis in both M1 and M2 lines revealed that the expression of three chrysanthemum class B genes CmAP3.1,CmAP3.2 and CmPI,was negatively correlated with phenotypic severity.This suggests that class B genes in chrysanthemum not only have conserved functions in determining petal identity but also were involved in the determinacy of the flower meristem.This study provides insights into the functions of class B genes in flower development,and is informative for dissecting the molecular mechanisms of flower development in chrysanthemum.
文摘THIS year's International AIDS Society Conference on HIV Pathogenesis, Treatment and Preven-/tion, held in Kuala Lumpur, Malaysia, made major headlines when Timothy Hendch, an American doctor, announced that two more cancer patients may have been cured of HIV after receiving bone-marrow transplants to treat lymphoma. Both patients had been taking retroviral medication, and continued to do so after the transplants as their viral levels sank until doctors were unable to find any traces of HIV in the patients' blood.
基金We gratefully acknowledge B Han from National Center for Gene Research, Chinese Academy of Sciences (CAS) and Rice Genome Resource Center (RGRC) for providing BAC clone, cDNA clone and Tosl7 insertion line. We thank Z-J Luo and M-J Chen from Shanghai Jiao Tong University for mutant screening and generation of F2 populations, X-Y Gao from Institute of Plant Physiology and Ecology, SIBS, CAS, for SEM, H Yu from Nation- al University Of Singapore for critical reading of this manuscript and H Ma from Fudan University for helpful discussion. This work was supported by funds from the National Basic Research Program of China (2009CB941500, 2006CB 101700), the National Natural Science Foundation of China (30725022, 30830014 and 90717109) and the Shanghai Leading Academic Discipline Project (B205).
文摘Although AGAMOUS-LIKE6 (AGL6) MADS-box genes are ancient with wide distributions in gymnosperms and angiosperms, their functions remain poorly understood. Here, we show the biological role of the AGL6-1ike gene, OsMADS6, in specifying floral organ and meristem identities in rice (Oryza sativa L.). OsMADS6 was strongly ex- pressed in the floral meristem at early stages. Subsequently, OsMADS6 transcripts were mainly detectable in paleas, lodicules, carpels and the integument of ovule, as well as in the receptacle. Compared to wild type plants, osmads6 mutants displayed altered palea identity, extra glume-like or mosaic organs, abnormal carpel development and loss of floral meristem determinacy. Strikingly, mutation of a SEPALLATA (SEP)-like gene, OsMADS1 (LHS1), enhanced the defect of osmads6 flowers, and no inner floral organs or glume-like structures were observed in whorls 2 and 3 of osmadsl-z osmads6-1 flowers. Furthermore, the osmadsl-z osmads6-1 double mutants developed severely indetermi- nate floral meristems. Our finding, therefore, suggests that the ancient OsMADS6 gene is able to specify "floral state" by determining floral organ and meristem identities in monocot crop rice together with OsMADS1.
文摘It is vital to determine the effective photoperiods of maize for making full use of tropical germplasm, which is the foundation for determining the effect of latitude and planting date on the development of photoperiod-sensitive maize cultivars. The objective of this study is to determine the photoperiod-sensitive inductive phase using reciprocal transfer between long- day (LD) (15 h d^-1) and short-day conditions (SD) (9 h d^-1). For Huangzao 4 and CML288, days to tassel and pollen shedding were recorded, and stem apical meristems (SAM) were observed by a laser scanning confocal microscope. The results show that the seedlings are insensitive to photoperiod when they are very young (juvenile). However, after this period, LD delays flowering and increases the leaf numbers below the inflorescence, and the length of the interval of the photoperiod-sensitive inductive phase is longer under LD conditions than under SD conditions. Transferred from SD to LD, plants show a sudden decrease in leaf numbers once sufficient SD has been received for flower commitment. While transferred from LD to SD, plants have a continuous increase in leaf numbers during the photoperiod sensitive inductive phase under LD conditions. At the same time, when plants are competent to flowers, the obvious morphology is the elongation of maize SAM. There is an obvious variance of the photoperiod sensitive phase under LD and SD conditions in different maize.
基金Acknowledgments The authors thank Dr Liying Du (Peking University, China) for technical help on the flow cytometric analysis. The authors also thank Dr Zhongchi Liu (University of Maryland, USA), Dr Chun-Ming Liu (Institute of Botany CAS, China), Dr Terry Matthew (University of Southampton, UK), Professor Daochun Kong (Peking University, China) and Dr Naomi Nakayama (Yale University, USA) for critical comments and valuable discussion. This work was supported by the National Natural Science Foundation of China (GN 30625002 to L-J Qu).
基金supported by The National Natural Science Foundation of China(31571588)。
文摘Background:Manual topping is a routine agronomic practice for balancing the vegetative and reproductive growth of cotton(Gossypium hirsutum)in China,but its cost-effectiveness has decreased over time.Therefore,there is an urgent need to replace manual topping with new approaches,such as biological topping.In this study,we examined the function of Gh REV transcription factors(a classⅢhomeodomain-leucine zipper family,HD-ZIPⅢ)in regulating the development of shoot apical meristem(SAM)in cotton with the purpose of providing candidate genes for biological topping of cotton in the future.Results:We cloned four orthologous genes of At REV in cotton,namely Gh REV1,Gh REV2,Gh REV3,and Gh REV4.All the Gh REVs expressed in roots,stem,leaves,and SAM.Compared with Gh REV1 and Gh REV3,the expression level of Gh REV2 and Gh REV4 was higher in the SAM.However,only Gh REV2 had transcriptional activity.Gh REV2 is localized in the nucleus;and silencing it via virus-induced gene silencing(VIGS)produced an abnormal SAM.Two key genes,Gh WUSA10 and Gh STM,which involved in regulating the development of plant SAM,showed about 50%reduction in their transcripts in VIGS-Gh REV2 plants.Conclusion:Gh REV2 positively regulates the development of cotton SAM by regulating Gh WUSA10 and Gh STM potentially.
文摘In wheat plants at the vegetative growth stage, the shoot apical meristem (SAM) produces leaf primordia. When reproductive growth is initiated, the SAM forms an inflorescence meristem (IM) that differentiates a series of spikelet meristem (SM) as the branch. The SM then produces a series of floret meristem (FM) as the branch. To identify the mechanisms that regulate formation of the reproductive meristems in wheat, we have investigated a leaf initiation mutant, fushi-darake (fdk) which was developed by ion beam mutagenesis. The morphological traits were compared in wild type (WT) and fdk mutant plants grown in the experimental field. WT plants initiated leaves from SAM at regular intervals in spiral phyllotaxy, while fdk plants had 1/2 alternate phyllotaxy with rapid leaf emergence. The fdk plants have increased numbers of nodes and leaves compared with WT plants. The time interval between successive leaf initiation events (plastochron) was measured in plants grown in a growth chamber. The fdk plants clearly show the rapid leaf emergence, indicating a shortened plastochron. Each tiller in fdk plants branches at the upper part of the culm. The fine structure of organ formation in meristems of fdk plants was examined by scanning electron microscopy (SEM). The SEM analysis indicated that fdk plants show transformation of spikelet meristems into vegetative shoot meristems. In conclusion, the fdk mutant has a heterochronic nature, i.e., both reproductive and vegetative programs were simultaneously in operation during the reproductive phase, resulting in a shortened plastochron and transformation of reproductive spikelets into vegetative shoots.
文摘To further study the floral organogenesis and discussing the floral origin of Phytolacca, the procedures of floral organogenesis were observed in Phytolacca esculenta and Phytolacca zhejiangensis. The results showed that the floral organogenesis was consistent in Phytolacca. Their sepals were 2/5 helix, and with counter-clockwise and clockwise, usually the first sepal located at non-median of abaxial side. The first sepal of Phytolacca esculenta was initiated at non-median of adaxial side. There was no evident relationship between sepal and stamen initiating position, and the stamens initiated on ring meristem, they initiated approximately at the same time, and when the androecium member was numerous, they initiated centrifugally, the outer stamen initiated irregularly. Carpel initiated alternately with inner stamens. And the carpels connected by septum, if the septum grew more, the carpel was syncarpous at morphology, otherwise the carpel was apocarpous at morphology. So the syncarpous and the apocarpous have no successively relationship on evolution. Ovule initiated inside the carpel and opposite to carpel. Androecium, carpel and ovule initiated at ring meristem.
文摘Different aspects of micropropagation through meristem culture for the production of virus indexed source plants, <i><span style="font-family:Verdana;">in vitro</span></i><span style="font-family:Verdana;"> tuberization and field evaluation of the </span><i><span style="font-family:Verdana;">in vitro</span></i><span style="font-family:Verdana;"> regenerated plants were studied on four commercial cultivars of potato (</span><i><span style="font-family:Verdana;">Solanum tuberosum</span></i><span style="font-family:Verdana;"> L.) viz., Diamant, Cardinal, Shilbilati and Lalpakri. The investigation was conducted at Rajshahi, Bangladesh from December 2010 to March 2012 to produce virus-free potato plantlets through meristem culture, shoot multiplications with root induction as well as their acclimatization and evaluation of morphological characters and tuber yield under field condition. Shoot tips of 25</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">30 day old field</span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""><span style="font-family:Verdana;">grown plants of above mentioned four cultivars were used for meristem isolation. After isolation, meristems of these varieties of potato were cultured on “M” shaped filter paper bridge in Murashige and Skoog (MS) liquid medium. Four different treatments of media formulations viz. 0.1 mg/L KIN + 0.1 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">, 0.1</span></span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">mg/L KIN + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">, 0.5 mg/L KIN + 0.1 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> and 0.5 mg/L KI</span></span><span style="font-family:;" "=""><span style="font-family:Verdana;">N + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> were used as plant growth regulators. From these formulations MS + 0.1 mg/L KIN + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> was found to be the best for </span></span><span style="font-family:Verdana;">the </span><span style="font-family:Verdana;">primary establishment of meristem culture. The primar</span><span style="font-family:Verdana;">ily</span><span style="font-family:Verdana;"> established meristems were subcultured on to MS semisolid basal medium supplemented with four different treatment combinations of hormones viz. 0.5 mg/L BA</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">+ 1.0 mg/L IBA;0.1 mg/L KIN + 0.1 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;">;0.5 mg/L BA + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> and 0.5 mg/L KIN + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> were used to identify the suitable media compositions for shoot proliferation. Results showed that out of these four media treatments the formulation 0.5 mg/L BA + 0.5 mg/L GA</span><sub><span style="font-family:Verdana;">3</span></sub><span style="font-family:Verdana;"> was found to be the best suitable for shoot generation. Among the four cultivars of potato higher frequency of shoot proliferation (number of shoots/explant and longest shoot length) was observed in Diamant, though the highest shoot formation (76%) was recorded in Cardinal. Virus free </span><i><span style="font-family:Verdana;">in vitro</span></i><span style="font-family:Verdana;"> grown potato plantlets were ob</span><span style="font-family:Verdana;">tained through DAS-ELISA test and used substantially for m</span><span style="font-family:Verdana;">icro-propagation. After gradual acclimatization of rooted plantlets of four potato cultivars</span></span><span style="font-family:Verdana;">,</span><span style="font-family:;" "=""><span style="font-family:Verdana;"> they were transferred into the field for cultivation and established successfully. It was observed from the field study of </span><i><span style="font-family:Verdana;">in vitro</span></i><span style="font-family:Verdana;"> meristem-derived plantlets that there were no virus-affected plants. The virus-free exotic varieties were much superior in all vegetative attributes and yield compare</span></span><span style="font-family:Verdana;">d</span><span style="font-family:Verdana;"> to those of indigenous varieties with producing potato plants of normal height. In contrast, the indigenous varieties took </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">longer time to tuber initiation and maturity, lower plant height and number of leaves per plant, </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">higher number of tubers but </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">lower amount of tuber weight per plant, and poorer tuber grade than the exotic varieties. However, the variety Cardinal exposed the best performances in the context of survival percentage of plantlets (90%), days to tuber initiation (DTI), </span><span style="font-family:Verdana;">a </span><span style="font-family:Verdana;">number of leaves per plant (NL), tuber weight per plant (343.40%) and the percentage of rich tuber grade.</span>
文摘Shoot meristems used for the study were exercised from the in vitro regenerated shoots cultured on MS medium supplemented with 0.5 mg/L of BAP for multiplication. The sensitivity of the in vitro regenerated was studied using shoot meristems of 0.5 cm. Shoot meristems were cultured on medium containing 10-100 mg/l kanamycin to determine the concentration that was lethal for multiple shoot induction and root induction. The response of shoot multiplication decreased (66.2%-6.2%) as the concentration of kanamycin increased (10.0-70.0 mg/L) with complete inhibition of shoot proliferation at 100 mg/L kanamycin. The rooting phase was very sensitive to kanamycin compared to shoot multiplication. The percentage of shoots that rooted decreased (53.8%-4.8%) with increase in the concentration of kanamycin (10.0-70.0 mg/l) on IBA and 2,4-D supplemented medium. For transformation studies, the shoot tips that were infected with Agrobacterium strain were placed on selection medium containing MS medium with 0.5 mg/L BAP and 100 mg/L kanamycin and scored for the putative transformed shoots. An average of 62.2% of shoot tips developed shoot buds from the base and the shoots reached a length of 0.5-1.0 cm at the end of 30 days of culture on the selective medium in comparison to control which showed no response. An average of 66.7% of the regenerated plants showed GUS expression on selection medium where 43.2% and 65% of GUS expression was recorded in the leaves and callus. Leaves and callus induced from the controls did not show GUS activity. Stable integration of nptII gene with the genomic DNA from these transformed plants was confirmed through PCR analysis. Our result presents an efficient regeneration system using in vitro derived shoot meristems for Agrobacterium mediated gene transfer.
文摘The ultrastructure of apical meristem cells was studied in Triticum aestivum L. cv. “Trizo” seedlings grown on soil without or enriched with selenium and survived 14 days’ stress caused by lead pollution in the soil. The soil treatments: control—the original soil;(Pb1)—50 mg·kg−1;(Pb2)—100 mg·kg−1;(Pb1 + Se1) —0.4 mg·kg−1 Se added to Pb1 treated soil;(Pb1 + Se2)—0.8 mg·kg−1 Se added to Pb1 treated soil;(Pb2 + Se1)—0.4 mg·kg−1 Se added to Pb2 treated soil;(Pb2 + Se2)—0.8 mg·kg−1 Se added to Pb2 treated soil were used. Light and other conditions were optimal for plant growth. A distinctive feature of the cells of the apical meristem of control plants was the absence of nuclear membranes. Proplastids were membrane vesicles 1 - 2 microns in diameter, filled with contents of varying degrees of density, from membrane vesicles containing only plastid DNA up to a fully formed structure of proplastids. In (Pb1)-plants, the amount of cytoplasmic ribosomes and proplastids in the meristematic cells was less than in the control. The structure of the forming proplastids was almost the same as that of the control plants. Signs of degradation of meristematic proplastids, such as a decrease of their diameter, observed in (Pb2)-plants. The introduction of selenium into lead contaminated soil increased the accumulation of Pb in plants, especially in the roots and apical meristem. In (Pb1 + Se1)-, (Pb1 + Se2)-, (Pb2 + Se1)-, and (Pb2 + Se2)-plants, the number of cytoplasmic ribosomes in meristematic cells increased, which indirectly indicates an increase in protein synthesis. Based on our concept about the formation (assembly) of proplastids in the cells of the apical meristem, we believe that toxic agents, such as lead, which inhibit the development of proplastids into chloroplasts in mesophyll cells, act on apical meristem cells at the stage when plastid DNA is replicated in the cytoplasm and is not yet surrounded by a plastid membrane.
基金supported by the National Natural Science Foundation of China (32071993, 32188102, 31971872, 31861143006,U2004204)Key Agricultural Technology Project(NK2022010302)。
文摘Increasing tiller number is a target of high-yield rice breeding. Identification of tiller-defect mutants and their corresponding genes is helpful for clarifying the molecular mechanism of rice tillering. Summarizing research progress on the two processes of rice tiller formation, namely the formation and growth of axillary meristem, this paper reviews the effects of genetic factors, endogenous hormones, and exogenous environment on rice tillering, finding that multiple molecular mechanisms and signal pathways regulating rice tillering cooperate rice tillering, and discusses future research objectives and application of its regulatory mechanism. Elucidation of theis mechanism will be helpful for breeding high-yielding rice cultivars with ideal plant type via molecular design breeding.