Highlights OsCAX2 is localized to tonoplast,and cadmium induces its expression.OsCAX2 overexpression reduces cadmium concentration in indica rice grains by 49.1%.Cadmium(Cd)exposure poses significant health risks to h...Highlights OsCAX2 is localized to tonoplast,and cadmium induces its expression.OsCAX2 overexpression reduces cadmium concentration in indica rice grains by 49.1%.Cadmium(Cd)exposure poses significant health risks to humans,and the International Agency for Research on Cancer has classified it as a Group I carcinogen.Cadmium undergoes minimal metabolism in the human body;consequently,prolonged Cd^(2+)exposure can cause severe damage to multiple organs including the liver,kidneys,lungs,bones,and immune system(Shao et al.2024).Rice,one of the three global staple crops,and Cd exposure in humans primarily occurs the consumption of contaminated rice grains.The contribution of rice to the total dietary Cd intake is over 50% for non-smoking Asian populations(Chen et al.2018;Shi et al.2020).展开更多
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
基金financially supported by the National Key R&D Program of China(2024YFD1200800)the Guangdong Basic and Applied Basic Research Foundation,China(2024A1515030094)。
文摘Highlights OsCAX2 is localized to tonoplast,and cadmium induces its expression.OsCAX2 overexpression reduces cadmium concentration in indica rice grains by 49.1%.Cadmium(Cd)exposure poses significant health risks to humans,and the International Agency for Research on Cancer has classified it as a Group I carcinogen.Cadmium undergoes minimal metabolism in the human body;consequently,prolonged Cd^(2+)exposure can cause severe damage to multiple organs including the liver,kidneys,lungs,bones,and immune system(Shao et al.2024).Rice,one of the three global staple crops,and Cd exposure in humans primarily occurs the consumption of contaminated rice grains.The contribution of rice to the total dietary Cd intake is over 50% for non-smoking Asian populations(Chen et al.2018;Shi et al.2020).
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.
