大豆根瘤钼转运关键基因的功能鉴定

Taking full advantage of symbiotic nitrogen fixation by legume-rhizobia is one of strategies to develop sustainable agriculture in China. Molybdenum (Mo) is a micronutrient essential for plant growth, which plays an important role in nitrogen fixation in nodules through participating in nitrogenase synthesis. Therefore, preferentially transport of Mo into nodules could be one of the effective way to increase nitrogen fixation efficiency. Based on our previously constructed recombinant inbred lines for nitrogen fixation efficiency analysis, we found one major QTL, qMoC-17 controlling both nodule number and Mo content. After fine mapping using residual heterozygous lines and their F2 population, the candidate gene was mapped to a 200-kb region in chromosome 17. After screening the total 22 candidate genes in qMoC-17 region by RNAi knockdown in transgenic hairy roots, we tentatively identified a transporter gene named GmMoT1 as the key gene responsible for Mo transport in nodules. In this study, firstly we are going to clarify the mechanism for Mo transport in nodules through functional characterization of Mo transporter GmMoT1 from physiological, biochemical and molecular aspects, and then to evaluate the application potential of GmMoT1 for increasing nitrogen fixation efficiency by investigating the nodule-specific GmMoT1-overexpression lines and analyzing the natural variations of GmMoT1 in the germplasm of “soybean core collection”. This study will provide the theoretical base for breeding cultivars with high nitrogen fixation efficiency.

充分发挥豆科作物共生固氮是保障我国农业可持续发展的有效措施。作为植物生长所必需的微量元素之一，钼参与根瘤固氮酶的合成，直接影响结瘤固氮效率。因此，利用生物学方法来实现钼在根瘤中的优先高效分配，是提高固氮效率的有效途径。我们利用一套用于根瘤固氮效率研究的大豆重组自交系遗传群体，定位到一个同时控制根瘤数量和钼含量的主效QTL位点qMoC-17，利用剩余杂合系以及次级F2群体进行精细定位后，将该QTL锁定在200kb区间；同时，对该区间的全部22个候选基因进行毛根体系RNAi干涉筛选，初步鉴定到一个转运蛋白基因（命名为GmMoT1），推测为根瘤钼转运关键基因。本研究首先将从生理、生化及分子层面，系统研究GmMoT1的生物学功能，解析钼在大豆根瘤中的运输机制；同时通过创制根瘤钼高效株系，并分析其自然变异规律，评估GmMoT1在提高固氮效率上的潜在应用价值，这将为选育固氮高效的作物品种提供理论基础。

充分发挥豆科作物共生固氮是保障我国农业可持续发展的有效措施。作为植物生长所必需的微量元素之一，钼参与根瘤固氮酶的合成，直接影响结瘤固氮效率。因此，利用生物学方法来实现钼在根瘤中的优先高效分配，是提高固氮效率的有效途径。我们首先利用正向遗传学方法鉴定到一个钼转运相关的遗传位点，并通过毛根筛选鉴定到一个候选基因MoT1。然后从生理、生化及分子层面，系统研究了该基因MoT1以及其同源基因MoT2的生物学功能，发现其对大豆根瘤固氮不可或缺；进一步机制研究发现，细胞内的活性氮信号可能是影响根瘤固氮能力的重要因素。另外，通过创制过表达株系，并分析其自然变异规律，我们评估了这些基因在提高固氮效率上的潜能，为选育固氮高效的作物品种提供理论基础。