Abstract:

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 GA₃ 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 1^st to 5^th 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^-1 GA₃ for 5 d on d534 seedlings， the plant height was 71.76% and 74.98% higher than that of untreated group （0 mg·L^-1 GA₃）. 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.

Key words: rice, d534 mutant, semi-dwarfism, late-heading, gibberellin

摘要：

水稻半矮秆突变体在株型改良和高产育种中具有重要价值。前期通过辐射诱变籼稻品种五山丝苗（R534）获得了半矮秆且抽穗期延迟突变体d534，分析了d534的表型、遗传模式和GA₃敏感性。大田性状分析发现，和野生型R534相比，d534的抽穗期延迟了7 d，株高下降了29.22 cm，降幅为26.86%。d534的穗及倒1至倒5节都明显缩短，长度分别为野生型的71.27%、68.75%、70.18%、85.17%、77.86%和71.18%，说明d534的目的基因调控穗及茎节的伸长。遗传分析发现，d534的矮化和迟抽穗性状受同一核基因控制，呈隐性遗传。内源GA₃含量测定发现，一叶一心期d534茎中GA₃含量为0.17 ng·g^-1，比R534降低了60.47%，表明d534的矮化与内源GA₃合成不足有关。用25和50 mg·L^-1外源GA₃处理一叶一心期幼苗5 d，d534的株高比未处理组（0 mg·L^-1 GA₃）增加了71.76%和74.98%，且超过了未处理组R534的株高，说明外源GA₃能回补d534的株高表型；qRT-PCR分析发现，与R534相比，d534茎和叶中OsGA20ox2和OsGA3ox2基因表达水平均显著下调，表明d534内源GA₃合成不足可能与OsGA20ox2和OsGA3ox2基因表达水平下调有关。明确了d534是茎节缩短且内源GA₃积累不足的矮化突变体，为解析d534半矮秆性状形成的生物学机理奠定了基础。

关键词: 水稻, d534突变体, 半矮秆, 迟抽穗, 赤霉素