东乡野生稻苗期抗旱基因qDR-12Dx的精细定位与克隆

Common wild rice (Oryza rufipogon Griff.) is the ancestor of cultivated rice, having been an important gene pool due to its survival in wild conditions and suffering from natural selection, various disasters and abiotic stresses. Nowadays, drought and shortage of water resource is becoming a serious constraint in rice production throughout the world, especially in our country. Therefore, it is of great significance to study genetic basis of drought resistance as well as to explore new genes of drought resistance in rice..qDR-12Dx, a seedling drought resistance QTL, was identified from the BC1F5 population derived from Dongxiang wild rice and a cultivar rice 'Xieqingzao B' by our laboratory. To clarify its biological function accurately, we constructed the nearly isogenic line (NIL) D359 for qDR-12Dx through continuous backcross, self-pollination and marker-assisted selection (MAS). Genetic analysis showed that, the phenotype of drought resistance of D359 was controlled by a single gene, and we preliminarily mapped it into a confined region about 0.79 cM on the long arm of chromosome 12, where no known gene involved in drought resistance has been identified. In this research, we will fine map and clone qDR-12Dx gene, and study its drought resistance machanism, of which the results will be helpful for developing drought resistance varieties of rice.

普通野生稻是栽培稻的祖先种，由于长期处于野生状态，经受了各种灾害和不良环境的自然选择，抗逆性较强，其遗传多样性远远大于栽培稻，是天然的基因库。为缓解干旱以及水资源短缺给世界尤其给我国水稻生产带来的严重影响，发掘水稻抗旱基因并进一步阐明抗旱机理已成为农业可持续发展的重要课题。.qDR-12Dx是我们利用东乡野生稻和栽培稻"协青早B"构建的BC1F5群体检测到的一个苗期抗旱相关主效QTL位点。为了准确地研究其生物学功能，我们进一步通过自交、回交以及分子标记辅助选择，构建了qDR-12Dx的近等基因系D359。遗传分析表明，D359的苗期抗旱性受单基因控制。该基因初步定位在水稻第12号染色体长臂0.79 cM的区间内，此区间内未见水稻抗旱基因克隆的报道。本研究拟精细定位并克隆qDR-12Dx基因，研究该基因的抗旱分子机理，为培育水稻抗旱新品种奠定理论基础。

qDR-12Dx是本课题组利用东乡野生稻和栽培稻“协青早B”构建的重组自交系群体检测到的一个苗期抗旱性主效QTL。本项目采用连续回交、自交、分子标记辅助选择以及严格的抗旱性表型鉴定筛选，构建了一份遗传稳定的qDR-12Dx基因强抗旱近等基因系NIL395；利用全基因组测序技术对东乡野生稻和普通栽培稻“协青早B”进行了全基因组测序，开发设计了东乡野生稻的高密度分子标记；利用近等基因系NIL395与回交亲本“协青早B”配置定位群体，将qDR-12Dx精细定位到第12号染色体2个标记之间，物理距离约为208.5 kb；根据水稻数据库注释，定位区间内共有14个候选基因；通过测序分析，发现在定位区间内的LOC_Os12g42280基因在编码区有3处碱基发生了变化，其中一处变化导致氨基酸发生改变；qRT-PCR结果显示，干旱条件下，该基因表达量在NIL395中较受体亲本“协青早B”显著上调；LOC_Os12g42280编码一个9-顺式-环氧类胡萝卜素双加氧酶，这类酶参与植物体内ABA的生物合成，在植物抗旱反应中起着重要的作用。qDR-12Dx基因有望成为一个很有潜力的基因资源用来培育水稻抗旱新品种。