低氮条件下内生放线菌OsiLf-2介导IAA调控途径提高水稻氮素利用的作用机制研究

目前我国水稻生产存在氮素利用率低和耐低氮能力差等问题，亟待开展多元化的应用基础研究以实现水稻“低氮肥高产量”的生产目标。内生菌与植物关系密切，可以通过多种作用机制提高植物对环境的适应能力。申请者前期筛选得到一株可以促进水稻生产并提高其耐低氮能力的内生放线菌OsiLf-2。研究发现，该菌株具有高产生长素IAA的特性。生长素是植物生长发育的关键调节因子，也参与植物逆境胁迫响应过程。但内生菌如何利用生长素调控植物氮素利用仍不清楚。在此基础上，申请者拟利用OsiLf-2的IAA合成缺陷突变体材料结合生理生化和分子生物学技术，在正常和缺氮条件下研究OsiLf-2如何调节自身和植物IAA的合成，并参与IAA信号转导途径影响水稻的氮代谢过程，进而解析OsiLf-2通过IAA途径提高水稻耐低氮和氮素高效利用的作用机理。该项目的研究结果将为利用内生菌资源解决水稻低氮肥利用效率的科学问题提供重要的理论指导。

The low-nitrogen utilization and low-nitrogen intolerance are serious problems that restrict the rice production of our country. Thus, developing diversified basic researches to achieve the production goal of "low nitrogen fertilizer and high yield" is currently in need. Endophytes are closely related to their host plants, and can improve the host adaptability in facing the environment changes in a variety of action mechanisms. The applicant has obtained an endophytic actinomycete OsiLf-2 which can promote rice production and improve its ability to tolerate the low nitrogen conditions. The previous study showed that OsiLf-2 has the capability of producing a large amount of auxin IAA. IAA is a key regulator of plant growth and development, and can also participate in the process of plant stress responses. However, how endophytes use IAA to regulate plant nitrogen utilization is still unclear. On this basis, the applicant intends to use the mutant materials of OsiLf-2 that lack the capability of IAA synthesis, and combine with physiological, biochemical and molecular biology techniques to study how OsiLf-2 regulates the synthesis of IAA in itself and in its host rice in normal or nitrogen-deficient conditions. The IAA signal transduction pathway affects the nitrogen metabolism process of rice tissues, and then the mechanism of OsiLf-2 enhancing the tolerance to the low-nitrogen stress and promoting the nitrogen utilization efficacy through the IAA pathway is analyzed. The results of this project will provide important theoretical guidance of using endophyte resources to solve the scientific problem of rice low-nitrogen fertilizer utilization efficiency.