水稻包穗突变体sui2的遗传分析和基因精细定位

Genetic analysis and fine mapping of a sheathed panicle mutant sui2 in rice(Oryza sativa L.)

水稻穗下倒一节间的伸长和发育对株型的形成起着重要作用,在水稻不育系中常见的包穗现象是由于穗下倒一节间的伸长和发育受阻造成的,深入研究水稻包穗分子机制能为水稻不育系株型的改良提供一定的理论意义。我们在粳稻Kitaake的组织培养后代中获得了1个包穗突变体sui2,其穗部被剑叶叶鞘包裹程度处于半包裹和全包裹之间,倒一节间严重缩短细胞学形态分析表明,倒一节间的缩短是由于节间薄壁细胞的伸长生长不足造成的。通过对sui2与IRAT129杂交后代分析表明,sui2为单基因显性突变。对该组合F2的608个正常单株遗传定位分析结果表明,候选基因SUI2被精细定位在4号染色体长臂端,由InDel标记S4-14.1和S4-14.2界定的110 kb的区域内。该区间内的编码基因在基因组序列水平上无差异,而基因LOC_Os04g39430表达量在突变体中升高了264倍,该基因编码1个参与油菜素内酯(brassinolide,BR)合成的细胞色素P450蛋白,是D11的等位基因。qRT-PCR分析结果表明,突变体中BR信号途径的基因表达量增高,预示着BR信号途径的基因可能参与了穗下倒一节间的伸长和发育的调控。

The elongation and development of rice uppermost internode plays an important role in plant architecture development.In general,the sheathed panicle phenomenon in rice sterility line is caused by the elongation and development hindrance of the uppermost internode.The study on molecular mechanisms underlying sheathed panicle would be helpful for improving plant architecture in sterility line.At the present study,we reported the study on a sheathed panicle mutant,named sui2,originated from a tissue-culture progeny.Its uppermost internode severely shortened,resulted in its pancleen closed by flag leaf sheath,without significantly length alternation at other internodes.The cytological analysis demonstrated that the shorten of the uppermost internode is caused by insufficient elongation of the parenchyma cells.Genetic analysis of the progeny derived from the cross-combination of sui2 and IRAT129 revealed that sui2 is a single gene dominant mutant.Linkage analysis to 608 normal individuals from F2 generation showed that SUI2 was located in a 110 kb region delimited by InDel marks S4-14.1 and S4-14.2 on the end of chromosome 4 long arm.The annotated genes on this region did not display any difference in genomic sequence,while the expression level of LOC_Os04g39430,encoding a cytochrome P450 protein and an allele of D11,increased by 264 times expression amount in mutant.Analysis of qRT-PCR for several crucial genes on BR(brasssinolide)signaling pathway showed that in mutant the expression level of all these genes increased,indicating that genes in BR signaling pathway may be involved in the regulation to the elongation and development of uppermost internode.