Analysis of Character and Gibberellin Sensitivity of Rice Dwarfism and Late-Heading Mutant d534
Rice semi-dwarf mutants play important roles in plant type improvement and high-yield breeding.Previously,a semi-dwarf mutant named d534 was obtained by mutagenesis from the indica rice cv.Wushan Simiao(R534).The phenotype,genetic module and GA,sensitivity of d534 were analyzed in this study.Field observations found that,compared with the wild type R534,d534 delayed to head for 7 d and plant height decreased 29.22 cm(by 26.86％).The panicle and the first internode from top 1st to 5th internode were significantly shortened by 71.27％,68.75％,70.18％,85.17％,77.86％and 71.18％compared with wild type in the length,indicating that the target gene of d534 would control the elongation of panicle and all internodes.Genetic analysis revealed that the phenotypes of dwarfism and late-heading were both controlled by the same recessive nuclear gene.The determination of endogenous GA3 content showed that the GA3 in the stem of d534 seedlings was 0.17 ng·g-1,which was 60.47％lower than that of R534,indicating that the phenotype of dwarfism in d534 was related to the lack of endogenous GA3.After treated with 25 and 50 mg·L-1GA3 for 5 d on d534 seedlings,the plant height was 71.76％and 74.98％higher than that of untreated group(0 mg·L-1GA3).Meanwhile,such a height was more than that of untreated R534 seedlings,indicating that exogenous GA3 would rescue the plant height of d534.qRT-PCR analysis showed that the expression levels of OsGA20ox2 and OsGA3ox2 genes in d534 stem and leaf were significantly down-regulated compared with R534,indicating that the insufficient synthesis of endogenous GA3 in d534 might be related to the down-regulation of OsGA20ox2 and OsGA3ox2 gene expression levels.This study confirmed that d534 was a semi-dwarf mutant with shortened internodes and insufficient endogenous GA3.It provided basis for revealing the biological mechanism underlying the semi-dwarfism in d534.
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