Rice seed germination marks the start of cultivation and influences subsequent seedling growth,and is affected by hormones and environmental factors.Ubiquitination plays a critical role in this process by regulating h...Rice seed germination marks the start of cultivation and influences subsequent seedling growth,and is affected by hormones and environmental factors.Ubiquitination plays a critical role in this process by regulating hormonal homeostasis.In the ubiquitination cascade,ubiquitin-conjugating enzymes(UBCs)function as ubiquitin carriers to determine linkage specificity of ubiquitin chains.In rice(Oryza sativa),39 UBC genes are identified,but only one gene OsUBC12 has been functionally studied to promote seed germination under low-temperatures in japonica rice.To elucidate the role of UBCs in seed germination,we generated CRISPR-Cas9 mutants for 23 UBC genes and overexpressed 20 members in rice.Among them,seven UBC genes(OsUBC4/6/7/12/25/27/48)were found to regulate seed germination,with OsUBC27 and OsUBC48 acting through the ABA pathway.Exogenous ABA inhibitors restored the germination rate of osubc27^(CR).RT-qPCR analysis revealed that the ABA synthesis genes OsNCED1-5 were significantly upregulated in the mutants.Further differential ubiquitination proteomics in knockout mutants and wild-type plants showed that OsUBC27 regulates ABA homeostasis by modulating ubiquitination of the ABA-degrading protein OsABA8ox1,thereby balancing seed dormancy and germination.Sequence analysis identified distinct haplotypes of the seven OsUBCs that showed differential distribution between japonica and indica subspecies.Our study provides valuable molecular targets for developing rice varieties resistant to seed vivipary.展开更多
Nuclear factor Y(NF-Y),a group of conserved transcription-factor complexes that consist of NF-YA,B,and C subunits,is essential for developmental regulation and for responses to environmental changes in eukaryotes.We p...Nuclear factor Y(NF-Y),a group of conserved transcription-factor complexes that consist of NF-YA,B,and C subunits,is essential for developmental regulation and for responses to environmental changes in eukaryotes.We previously found that some NF-Y genes,such as OsNF-YA8,were expressed specifically in the endosperm of rice.In the present study,overexpression of OsNF-YA8 in rice resulted in reduced plant height due to suppressed cell elongation in internodes.Gibberellin(GA)biosynthetic genes,including OsCPS1,OsGA20ox1,and OsGA20ox2,were down-regulated.OsNF-YA8 bound to the promoters of these genes to repress their expression.Endogenous GA content was decreased in OsNF-YA8 overexpressors,whose dwarf phenotype could be partially rescued by exogenous GA treatment.The findings suggested that ectopic expression of OsNF-YA8 causes defective GA biosynthesis in vegetative stage.Heading date in OsNF-YA8 overexpressors was delayed,especially under short-day conditions.OsNFYA8 bound to the promoter of Heading Date 3a(Hd3a),the florigen gene in rice,to negatively regulate flowering.Either ectopic activation or knockout of OsNF-YA8 impaired seed development,as indicated by reduced seed size and increased grain chalkiness.These results suggest that ectopic expression of the endosperm-specific OsNF-YA8 in rice disrupts both vegetative and reproductive development.展开更多
Following double fertilization,plant endosperm nuclei undergo syncytial divisions,followed by synchro-nous cellularization.Cellularization is a key event during endosperm development,but our understanding of its regul...Following double fertilization,plant endosperm nuclei undergo syncytial divisions,followed by synchro-nous cellularization.Cellularization is a key event during endosperm development,but our understanding of its regulation is limited to Arabidopsis.In this study we show that OsbZIP76 regulates cellularization in rice(Oryza sativa).Activation of OsbZIP76 coincided with the initiation of cellularization,and its knockdown or knockout mutants exhibited precocious cellularization.Genes involved in en-dosperm development or starch biosynthesis were pre-maturely activated in the osbzip76 caryopsis.As a putative transcription factor,OsbZIP76 alone lacked transcriptional activation activity;however,it interacted with the nuclear factor Y(NF-Y)family transcription factors OsNF-YB9 and OsNF-YB1 in yeast and in planta.OsbZIP76 and OsNF-YB9 were predominantly expressed in the endosperm and the proteins colocalized.Seeds of osnf-yb1 and osbzip76 mu-tants showed reduced size and reduced apparent amylose content.The parent-of-origin-dependent expression of OsbZIP76 is variable in different rice accessions.In sum-mary,OsbZIP76 is an endosperm-expressed imprinted gene that regulates endosperm development in rice.展开更多
Cellularization is a key event in endosperm development.Polycomb group(PcG)genes,such as Fertilization-Independent Seed 2(FIS2),are vital for the syncytium-to-cellularization transition in Arabidopsis plants.In this s...Cellularization is a key event in endosperm development.Polycomb group(PcG)genes,such as Fertilization-Independent Seed 2(FIS2),are vital for the syncytium-to-cellularization transition in Arabidopsis plants.In this study,we found that OsEMF2a,a rice homolog of the Arabidopsis PcG gene Embryonic Flower2(EMF2),plays a role similar to that of FIS2 in regard to seed development,although there is limited sequence similarity between the genes.Delayed cellularization was observed in osemf2a,associated with an unusual activation of type I MADS-box genes.The cell cycle was persistently activated in osemf2a caryopses,which was likely caused by cytokinin overproduction.However,the overaccumulation of auxin was not found to be associated with the delayed cellularization.As OsEMF2a is a maternally expressed gene in the endosperm,a paternally inherited functional allele was unable to recover the maternal defects of OsEMF2a.Many imprinted rice genes were deregulated in the defective hybrid seeds of osemf2a(♀)/9311(♂)(m9).The paternal expression bias of some paternally expressed genes was disrupted in m9 due to either the activation of maternal alleles or the repression of paternal alleles.These findings suggest that OsEMF2a-PRC2-mediated H3K27me3 is necessary for endosperm cellularization and genomic imprinting in rice.展开更多
基金supported by the Zhejiang Provincial Natural Science Foundation,China(ZCLMS25C1302)the Central Public-interest Scientific Institution Basal Research Fund(CPSIBRF-CNRRI-202408)the Agricultural Science and Technology Innovation Program(ASTIP)
文摘Rice seed germination marks the start of cultivation and influences subsequent seedling growth,and is affected by hormones and environmental factors.Ubiquitination plays a critical role in this process by regulating hormonal homeostasis.In the ubiquitination cascade,ubiquitin-conjugating enzymes(UBCs)function as ubiquitin carriers to determine linkage specificity of ubiquitin chains.In rice(Oryza sativa),39 UBC genes are identified,but only one gene OsUBC12 has been functionally studied to promote seed germination under low-temperatures in japonica rice.To elucidate the role of UBCs in seed germination,we generated CRISPR-Cas9 mutants for 23 UBC genes and overexpressed 20 members in rice.Among them,seven UBC genes(OsUBC4/6/7/12/25/27/48)were found to regulate seed germination,with OsUBC27 and OsUBC48 acting through the ABA pathway.Exogenous ABA inhibitors restored the germination rate of osubc27^(CR).RT-qPCR analysis revealed that the ABA synthesis genes OsNCED1-5 were significantly upregulated in the mutants.Further differential ubiquitination proteomics in knockout mutants and wild-type plants showed that OsUBC27 regulates ABA homeostasis by modulating ubiquitination of the ABA-degrading protein OsABA8ox1,thereby balancing seed dormancy and germination.Sequence analysis identified distinct haplotypes of the seven OsUBCs that showed differential distribution between japonica and indica subspecies.Our study provides valuable molecular targets for developing rice varieties resistant to seed vivipary.
基金the National Natural Science Foundation of China(31701392 and 32170344)the Six Talent Peaks Project in Jiangsu Province(NY-142)+1 种基金the Jiangsu Province Government(JBGS[2021]001)the Independent Scientific Research Project Funds of the Jiangsu Key Laboratory of Crop Genomics and Molecular Breeding(PLR202101).
文摘Nuclear factor Y(NF-Y),a group of conserved transcription-factor complexes that consist of NF-YA,B,and C subunits,is essential for developmental regulation and for responses to environmental changes in eukaryotes.We previously found that some NF-Y genes,such as OsNF-YA8,were expressed specifically in the endosperm of rice.In the present study,overexpression of OsNF-YA8 in rice resulted in reduced plant height due to suppressed cell elongation in internodes.Gibberellin(GA)biosynthetic genes,including OsCPS1,OsGA20ox1,and OsGA20ox2,were down-regulated.OsNF-YA8 bound to the promoters of these genes to repress their expression.Endogenous GA content was decreased in OsNF-YA8 overexpressors,whose dwarf phenotype could be partially rescued by exogenous GA treatment.The findings suggested that ectopic expression of OsNF-YA8 causes defective GA biosynthesis in vegetative stage.Heading date in OsNF-YA8 overexpressors was delayed,especially under short-day conditions.OsNFYA8 bound to the promoter of Heading Date 3a(Hd3a),the florigen gene in rice,to negatively regulate flowering.Either ectopic activation or knockout of OsNF-YA8 impaired seed development,as indicated by reduced seed size and increased grain chalkiness.These results suggest that ectopic expression of the endosperm-specific OsNF-YA8 in rice disrupts both vegetative and reproductive development.
基金This work was supported by the National Natural Science Foundation of China (31771744 and 31571623)Science Fund for Distinguished Young Scholars of Jiangsu Province (BK20180047)Natural Science Foundation of Jiangsu Province(BK20160454)and the Priority Academic Development of Jiangsu Higher Education Institutions.
文摘Following double fertilization,plant endosperm nuclei undergo syncytial divisions,followed by synchro-nous cellularization.Cellularization is a key event during endosperm development,but our understanding of its regulation is limited to Arabidopsis.In this study we show that OsbZIP76 regulates cellularization in rice(Oryza sativa).Activation of OsbZIP76 coincided with the initiation of cellularization,and its knockdown or knockout mutants exhibited precocious cellularization.Genes involved in en-dosperm development or starch biosynthesis were pre-maturely activated in the osbzip76 caryopsis.As a putative transcription factor,OsbZIP76 alone lacked transcriptional activation activity;however,it interacted with the nuclear factor Y(NF-Y)family transcription factors OsNF-YB9 and OsNF-YB1 in yeast and in planta.OsbZIP76 and OsNF-YB9 were predominantly expressed in the endosperm and the proteins colocalized.Seeds of osnf-yb1 and osbzip76 mu-tants showed reduced size and reduced apparent amylose content.The parent-of-origin-dependent expression of OsbZIP76 is variable in different rice accessions.In sum-mary,OsbZIP76 is an endosperm-expressed imprinted gene that regulates endosperm development in rice.
基金supported by grants from the National Key R&D Program of China(2016YFD0100902)the National Natural Science Foundation of China(31701392)+1 种基金the Science Fund for Distinguished Young Scholars of Jiangsu Province(BK20180047)the Priority Academic Development of Jiangsu Higher Education Institutions.
文摘Cellularization is a key event in endosperm development.Polycomb group(PcG)genes,such as Fertilization-Independent Seed 2(FIS2),are vital for the syncytium-to-cellularization transition in Arabidopsis plants.In this study,we found that OsEMF2a,a rice homolog of the Arabidopsis PcG gene Embryonic Flower2(EMF2),plays a role similar to that of FIS2 in regard to seed development,although there is limited sequence similarity between the genes.Delayed cellularization was observed in osemf2a,associated with an unusual activation of type I MADS-box genes.The cell cycle was persistently activated in osemf2a caryopses,which was likely caused by cytokinin overproduction.However,the overaccumulation of auxin was not found to be associated with the delayed cellularization.As OsEMF2a is a maternally expressed gene in the endosperm,a paternally inherited functional allele was unable to recover the maternal defects of OsEMF2a.Many imprinted rice genes were deregulated in the defective hybrid seeds of osemf2a(♀)/9311(♂)(m9).The paternal expression bias of some paternally expressed genes was disrupted in m9 due to either the activation of maternal alleles or the repression of paternal alleles.These findings suggest that OsEMF2a-PRC2-mediated H3K27me3 is necessary for endosperm cellularization and genomic imprinting in rice.
