水稻生长素糖基转移酶基因OsIAGLU促进种子萌发与幼苗建成的功能分析

Seed germination and seedling establishment are one of the key factors influencing the yield of rice in direct-seeding producation. It is important to reveal the functions of genes involved in seed germination and seedling establishment in order to improve the field emergence of direct seeding in rice. In our previous study, the novel funcations of auxin glycosyltransferase gene OsIAGLU were identified in rice, involving in the regulation of seed germination and seedling establishment. It is speculated that OsIAGLU promotes seed germination and seedling establishment through the regulation of dynamic balance of auxin level during seed development and seed germination stages. In this study, biochemical analysis of OsIAGLU will be carried out to clarify its glycosylation to different types of auxins. With CRISPR/Cas9 approach the mutants of OsIAGLU in rice will be generated to reveal the gene regulation on the contents of free and bound auxins during seed development and germination, and to further clarify the influences of auxin level on seed germination and seedling establishment. Meanwhile the mechanism of OsIAGLU involved in the regulations of seed germination and seedling establishment will be further discussed with the combined physiological, molecular and transcriptome approaches. The results will provide the theoretical basis for the genetic improvements of seed germination and seedling establishment of rice for direct-seeding production in the future.

水稻种子萌发与幼苗建成是影响直播稻产量的关键因子之一，解析调控种子萌发与幼苗建成相关基因的功能，对提高直播稻种子田间出苗具有重要意义。本项目前期研究发现，水稻生长素糖基转移酶基因OsIAGLU具有调控种子萌发与幼苗建成的作用功能，推测该基因通过调控种子发育和萌发过程中生长素动态平衡，促进种子萌发与幼苗建成。本项目拟在前期研究基础上，对水稻生长素糖基转移酶OsIAGLU开展生化功能研究，明确该酶对不同类型生长素的糖基化修饰作用；利用CRISPR/Cas9基因敲除技术获得水稻OsIAGLU突变体，分析该基因对种子发育和萌发过程中游离态和束缚态生长素含量的调控作用，明确生长素水平对种子萌发与幼苗建成的影响；进一步结合生理、分子以及转录组测序技术等，探讨基因参与种子萌发与幼苗建成的作用机制。研究结果可为今后遗传改良直播稻种子萌发与幼苗建成性状提供理论基础。

种子活力是水稻直播的重要性状。本研究从水稻中克隆了一个吲哚-3-乙酸β-葡萄糖基转移酶OsIAGLU，并着重研究了其对种子活力的影响。OsIAGLU突变后会导致水稻种子活力降低。定量RT-PCR分析表明，OsIAGLU在种子发育后期及萌发前期表达量较高，且受吲哚-3-乙酸（IAA）和脱落酸（ABA）诱导表达。转录组分析表明，IAA和ABA相关基因参与OsIAGLU调控的种子活力。与野生型（WT）相比，osiaglu突变体萌发种子中游离IAA和ABA水平较高。当外源IAA和ABA处理osiaglu突变体和WT植株时，osiaglu突变体对ABA更敏感，而对IAA不敏感，但外源IAA可增强ABA诱导的水稻种子活力的降低。与野生型相比，osiaglu突变体萌发种子中OsABI3和OsABI5的表达持续升高。因此，我们推测OsIAGLU调控水稻种子活力可能是通过调节IAA和ABA水平来改变OsABIs在水稻种子萌发过程中的表达。通过对水稻种质资源SNP数据的分析，在籼稻材料中，OsIAGLU有两个单倍型与种子活力呈正相关。这项研究为OsIAGLU对种子活力的影响及其在水稻育种中的应用提供了重要信息。