ABA调控玉米灌浆速率的分子机制

ABA stimulate the expression of starch synthesis genes and elevate the starch synthesis enzymes' activities during grain filling, and improve the grain filling rate. However, the molecular mechanism involved in the ABA-regulated expression of starch synthetic genes remain unclearly. In the previous studies, we found that the accumulation of ABI4 gene in maize endosperm was induced by ABA, and then the ABI4 protein interacts with a CACCG motif in the zsS1 promoter and increase the expression of the zsS1 gene. Mutants analysis showed that there are 10 key genes invovled in starch synthesis in maize kenerl: Sh2、Bt2、Bt1、zsS1、Su2、Du1、Wx、Ae、Su1 and Isa2, promoters analysis of the 10 genes indicated that they all have ABI4 binging motif in their promoters, thus, it probably that these gene's expression should be regulated by ABA through ABI4 protein. In the project, we plan to analyze the expression of these genes by ABA treatment in maize endosperm, and analyze the role of ABI4 protein in this process by using the technology of transient expression, site mutation, EMSA and genetic modification technology, which could reveal the molecular mechanism of accelerating grain filling rate of grain by ABA.

灌浆期作物籽粒中ABA能促进淀粉合成相关酶基因的表达，增加淀粉合成相关酶的活性，最终促进作物灌浆速率，长期以来人们对其中的分子机制并不了解。前期研究中我们发现，ABA能通过诱导玉米胚乳中ABI4基因的表达，然后ABI4蛋白与 zsS1启动子中的CACCG motif相结合促进zsS1基因的表达。对突变体的研究证明，玉米籽粒中与淀粉合成相关的酶类基因有Sh2、Bt2、Bt1、zsS1、Su2、Du1、Wx、Ae、Su1和Isa2等10个，对这10个基因启动子的分析发现，这些启动子中都存在ABI4蛋白的结合基序，因此ABA很可能也通过ABI4蛋白对这些基因的表达进行调控。本项目将在此基础上，分析玉米胚乳中ABA对其它9个淀粉合成关键基因表达的诱导，同时结合瞬时表达、定点突变、EMSA以及转基因过表达或基因敲除等技术，分析ABI4蛋白在这其中的作用途径，揭示ABA促进作物灌浆速率的分子机制。