拟南芥转录因子MYB30的泛素化修饰和SUMO化修饰共同调节ABA信号转导的机理研究

植物激素ABA在植物生长发育和外界信号响应过程中具有重要的调控作用。而泛素介导的蛋白质降解和SUMO化修饰，在生物体维持自身正常生长发育和适应环境过程中同样起着重要作用。在动物细胞中，已发现SUMO化修饰可以诱导蛋白的泛素化修饰，但植物中这两种修饰的关系并不清楚。之前的研究发现，拟南芥转录因子MYB30负调控ABA信号转导，而SUMO化修饰可以通过抑制MYB30蛋白的降解参与调节ABA信号途径。进一步研究发现，MYB30蛋白的降解是由泛素化修饰途径介导的。我们推测MYB30蛋白的SUMO化修饰可能是通过抑制MYB30蛋白的泛素化修饰起作用的。本项目希望通过鉴定MYB30蛋白的泛素化修饰位点，通过突变SUMO化修饰与泛素化修饰的关键位点了解两种修饰间如何相互调节，让我们对它们如何共同调节MYB30蛋白的降解进而参与ABA信号转导，以及植物中SUMO化修饰与泛素化修饰的关系有更加深入的了解。

The phytohormone abscisic acid (ABA) plays an essential role in plant development, including seed development, dormancy, germination, vegetative growth and during the response of the plant to biotic and abiotic stresses. We found that the Arabidopsis transcription factor MYB30 negatively regulates the ABA response, myb30 mutants are hypersensitive to ABA during germination and seedling growth. We also found the Arabidopsis SUMO E3 ligase SIZ1 mediates the sumoylation of MYB30 and the sumoylation of MYB30 plays an important role in ABA signaling. In wild-type seedlings, the protein stability of MYB30 is not affected by ABA, but ABA induces the degradation of MYB30 in siz1 mutant, suggesting that the sumoylation alters protein stability of MYB30. A further study found that the degradation of MYB30 is controlled by the ubiquitination. Post-translational control of protein degradation by the ubiquitin proteasome system (UPS) is a highly regulated process essential for the proper growth and development, several E3 ubiquitin ligases have been found to play a variety of roles in ABA signaling. We hope we can identify the ubiquitination sites in MYB30 and find out how ubiquitination functions in ABA response. In mammals, the sumoylation can promote the ubiquitination and ultimately led to protein degradation via the proteasome pathway, but the relationship between these two modifications in plant is still unclear. The study of MYB30 is a good chance to make the relationship clear, because MYB30 can be modified by these two modifications and both of them mediate the degradation of MYB30. We hope that we can figure out how sumoylation and ubiquitination regulate the degradation of MYB30 together, and how these modifications regulate the MYB30 downstream genes expression together to mediate the ABA response, so we can understand the relationship between these two modifications in plant through the study of ubiquitination and sumoylation of MYB30.