Panicle number per plant,grain number per panicle,and grain weight are three key factors influencing rice grain yield.Gn1a,a major QTL for grain number per panicle,encodes the cytokinin oxidase/dehydrogenase(CKX)OsCKX...Panicle number per plant,grain number per panicle,and grain weight are three key factors influencing rice grain yield.Gn1a,a major QTL for grain number per panicle,encodes the cytokinin oxidase/dehydrogenase(CKX)OsCKX2.While the use of elite Gn1a alleles has been well documented in indica rice cultivars,their potential in japonica rice remains largely unexplored.In this study,we characterized three suppressor mutants of the rice cytokinin receptor mutant pal1/ohk4 and found that all causal genes were novel alleles of Gn1a identified through the MutMap approach.These three suppressor mutants caused single amino acid substitutions in the FAD-binding domain(G556D and G156D)and the cytokinin-binding domain(Y357C),resulting in significantly reduced enzymatic activity of OsCKX2 and elevated cytokinin levels in the panicle.Haplotype analysis of Gn1a using a natural population from the 3K Rice Genomes Project showed that G556D,G156D,and Y357C were novel alleles of Gn1a.G556,G156,and Y357 were highly conserved,whereas four natural variants G54A,A105V,H116R,and N535K identified in different haplotypes of Gn1a showed extremely low conservation.By backcrossing the suppressor mutants with their original wild-type Huaidao 5,an elite japonica rice variety,we developed improved lines carrying only the gn1a mutation.The improved lines showed a significant increase in grain number per panicle,grain weight,panicle number per plant,plant height,and stem thickness,leading to a 25.7%-28.7%increase in grain yield per plot compared with Huaidao 5.This study provides valuable Gn1a alleles for synergistic improvement of the three key yield factors and offers germplasm resources for high-yielding breeding in japonica rice.展开更多
As an important yield component,rice tiller number controls panicle number and determines grain yield.Regulation of rice tiller number by chloroplast pentatricopeptide repeat(PPR)proteins has not been reported previou...As an important yield component,rice tiller number controls panicle number and determines grain yield.Regulation of rice tiller number by chloroplast pentatricopeptide repeat(PPR)proteins has not been reported previously.Here,we report the rice reduced culm number22(rcn22)mutant,which produces few tillers owing to suppressed tiller bud elongation.Map-based cloning revealed that RCN22 encodes a chloroplast-localized P-type PPR protein.We found that RCN22 specifically binds to the 5′UTR of RbcL mRNA(encoding the large subunit of Rubisco)and enhances its stability.The reduced abundance of RbcL mRNA in rcn22 leads to a lower photosynthetic rate and decreased sugar levels.Consequently,transcript levels of DWARF3(D3)and TEOSINTE BRANCHED1(TB1)(which encode negative regulators of tiller bud elongation)are increased,whereas protein levels of the positive regulator DWARF53(D53)are decreased.Furthermore,high concentrations of sucrose can rescue the tiller bud growth defect of the rcn22 mutant.On the other hand,TB1 directly binds to the RCN22 promoter and downregulates its expression.The tb1/rcn22 double mutant shows a tillering phenotype similar to that of rcn22.Our results suggest that the TB1–RCN22–RbcL module plays a vital role in rice tiller bud elongation by affecting sugar levels.展开更多
基金supported by the Biological Breeding-National Science and Technology Major Project,China(Grant No.2023ZD0406801)the National Natural Science Foundation of China(Grant No.32300278)+2 种基金the Key R&D Plan of Shandong Province,China(Grant No.2024LZGC009)the Innovation Program of Chinese Academy of Agricultural Sciences(Grant No.CAAS-CSCB-202402)the Science and Technology Innovation Project of Shandong Academy of Agricultural Sciences,China(Grant No.CXGC2025B09).
文摘Panicle number per plant,grain number per panicle,and grain weight are three key factors influencing rice grain yield.Gn1a,a major QTL for grain number per panicle,encodes the cytokinin oxidase/dehydrogenase(CKX)OsCKX2.While the use of elite Gn1a alleles has been well documented in indica rice cultivars,their potential in japonica rice remains largely unexplored.In this study,we characterized three suppressor mutants of the rice cytokinin receptor mutant pal1/ohk4 and found that all causal genes were novel alleles of Gn1a identified through the MutMap approach.These three suppressor mutants caused single amino acid substitutions in the FAD-binding domain(G556D and G156D)and the cytokinin-binding domain(Y357C),resulting in significantly reduced enzymatic activity of OsCKX2 and elevated cytokinin levels in the panicle.Haplotype analysis of Gn1a using a natural population from the 3K Rice Genomes Project showed that G556D,G156D,and Y357C were novel alleles of Gn1a.G556,G156,and Y357 were highly conserved,whereas four natural variants G54A,A105V,H116R,and N535K identified in different haplotypes of Gn1a showed extremely low conservation.By backcrossing the suppressor mutants with their original wild-type Huaidao 5,an elite japonica rice variety,we developed improved lines carrying only the gn1a mutation.The improved lines showed a significant increase in grain number per panicle,grain weight,panicle number per plant,plant height,and stem thickness,leading to a 25.7%-28.7%increase in grain yield per plot compared with Huaidao 5.This study provides valuable Gn1a alleles for synergistic improvement of the three key yield factors and offers germplasm resources for high-yielding breeding in japonica rice.
基金Biological Breeding-National Science and Technology Major Project of China(2023ZD0406801)Innovation Program of Chinese Academy of Agricultural Sciences(CAAS-CSCB-202402)+1 种基金National Natural Science Foundation of China(32270373,32270653)Agricultural Variety Improvement Project of Shandong Province,China(2021LZGC020).
文摘As an important yield component,rice tiller number controls panicle number and determines grain yield.Regulation of rice tiller number by chloroplast pentatricopeptide repeat(PPR)proteins has not been reported previously.Here,we report the rice reduced culm number22(rcn22)mutant,which produces few tillers owing to suppressed tiller bud elongation.Map-based cloning revealed that RCN22 encodes a chloroplast-localized P-type PPR protein.We found that RCN22 specifically binds to the 5′UTR of RbcL mRNA(encoding the large subunit of Rubisco)and enhances its stability.The reduced abundance of RbcL mRNA in rcn22 leads to a lower photosynthetic rate and decreased sugar levels.Consequently,transcript levels of DWARF3(D3)and TEOSINTE BRANCHED1(TB1)(which encode negative regulators of tiller bud elongation)are increased,whereas protein levels of the positive regulator DWARF53(D53)are decreased.Furthermore,high concentrations of sucrose can rescue the tiller bud growth defect of the rcn22 mutant.On the other hand,TB1 directly binds to the RCN22 promoter and downregulates its expression.The tb1/rcn22 double mutant shows a tillering phenotype similar to that of rcn22.Our results suggest that the TB1–RCN22–RbcL module plays a vital role in rice tiller bud elongation by affecting sugar levels.
