转录因子OsDof15调控水稻苗期耐盐性的分子基础

Salt stress greatly affects plant growth and development, which is an important limiting factor for crop yield production. Identifying key factors improving crop salt tolerance from germplasm resources to cultivate tolerant-crop varieties with high quality and high yield has become an urgent task for sustainable development of grain production in China. Accumulating data in our laboratory, and the international and domestic researches as well, all have shown that ethylene is an important regulator of salt tolerance in plants. In order to mining important genes of salt tolerance in rice, our previous study found that the knockout mutant seedlings of transcription factor gene OsDof15 showed decreased salt tolerance, while OsDof15 overexpression transgenic line seedlings displayed increased salt tolerance, evidencing that transcription factor OsDof15 positively affects salt tolerance of rice seedlings. Moreover, OsDof15 negatively regulates the expression of ethylene biosynthesis genes and ethylene content, indicating that OsDof15 might transcriptionally modulate ethylene biosynthesis. However, it is unclear whether the OsDof15-improved rice resistance to salt stress is attributed to the regulation of ethylene biosynthesis. If this answer is yes, then how OsDof15 transcriptionally controls the expression of ethylene biosynthesis genes. Based on the above results, the project will first conduct the physiological function and expression characters of OsDof15 in response to salt stress. The next step is to reveal the biochemical and genetic basis of OsDof15 in the transcriptional regulation of ethylene biosynthesis genes. Then the project will address how OsDof15 responds to the salt stress and triggers transcriptional regulation of ethylene biosynthesis to improve rice seedling salt tolerance. The implement of the project will provide useful genes to rice breeding, and importantly, the knowledge gained from the research will guide crop breeders to speed up the cultivation of salt tolerant crop varieties.

盐胁迫影响植物生长发育，是导致作物减产的重要因子；挖掘作物自身耐盐基因资源，培育耐逆优质高产作物新品种已成为我国粮食生产急需解决的重大课题。我们及国际国内同行的研究均表明，乙烯及其生物合成是调控植物耐盐性的重要因子。为了挖掘水稻耐盐的重要基因，我们实验室前期研究发现，转录因子OsDof15功能缺失突变体苗期耐盐性降低，而其过表达材料则相反；且OsDof15负调控乙烯生物合成基因表达和乙烯含量，表明OsDof15是影响水稻苗期耐盐性的重要调控因子，但该因子如何调控水稻耐盐性的分子机理不清楚。本项目拟在以上研究基础上，通过鉴定其应答逆境胁迫的表达及其调控水稻苗期耐盐性的生理功能，剖析OsDof15调控水稻乙烯生物合成基因表达和耐盐性的生化及遗传基础，阐明其应答盐胁迫调控水稻苗期乙烯生物合成及耐盐性的分子途径。研究结果不仅为水稻耐盐性育种提供有用的重要基因，还可为农作物分子设计育种提供理论指导。

盐胁迫影响植物生长发育，是导致作物减产的重要因子；挖掘作物自身耐盐基因资源，培育耐逆优质高产作物新品种已成为我国粮食生产急需解决的重大课题。乙烯作为植物生长发育调控激素，可以抑制水稻初生根生长，同时乙烯也是一种逆境植物激素，但乙烯是否参与盐胁迫条件对根的抑制作用尚不清楚。本研究表明，水稻DOF类转录因子OsDOF15可以抑制水稻幼苗根生长，而且通过转录组数据发现OsDOF15可以调控乙烯生物合成途径关键基因的表达，进一步实验验证OsDOF15可直接结合乙烯合成关键酶编码基因ACS1的启动子并抑制其表达。而OsDOF15的基因表达又受到盐胁迫抑制，从而导致盐胁迫条件下ACS1基因表达上调，乙烯合成增加，水稻幼苗根生长受到抑制。因此本工作揭示了盐胁迫条件下乙烯介导幼苗根生长发育的分子机理，同时还拓展了OsDOF15在调控根发育中的多种途径研究。上述结果为水稻耐盐性育种提供有用的重要基因，进而为农作物分子设计育种提供理论指导。