气孔运动日节奏中光调节保卫细胞RopGEF2水平和活性的分子机制研究

自然光照下气孔运动呈现早晨逐渐开放、午后逐渐关闭的日节奏，但其调控机制目前还不清楚。鸟苷酸交换因子RopGEF2是红光诱导气孔开放的负调控因子，前期研究发现ropgef2突变体气孔开度在12:00-16:00明显大于野生型；保卫细胞中RopGEF2的mRNA和蛋白水平存在先升高、后下降的日变化，MG132能抑制RopGEF2的降解；且红光活化的K1激酶能将RopGEF2磷酸化；表明RopGEF2受到了转录和翻译后修饰的调节。本项目拟在已有基础上利用生理生化及遗传学的研究方法重点研究：光信号通路中关键转录因子在保卫细胞中对RopGEF2的转录调节作用；光下K1的活性变化特征及其对RopGEF2的活性、气孔运动的影响；RopGEF2的磷酸化、泛素化与其蛋白稳定性之间的关系。本项目研究将揭示光通过调节保卫细胞中RopGEF2的水平和活性来抑制气孔过度开放的机制，也将丰富气孔运动的调控网络。

Stomatal apertures undergo gradual increase in the morning and gradual decrease afternoon under natural condition. However, the underline mechanism has not been completely understood. Guanine nucleotide exchange factor RopGEF2 is a negative regulator in red light-induced stomatal opening. Our recent works revealed that the stomatal apertures of ropgef2 mutant were larger than these of wild type from 12:00 noon to 4:00 pm. The mRNA and protein level of RopGEF2 in guard cells also exhibited a gradual increase in the morning and gradual decrease afternoon, and MG132 inhibited the degradation of RopGEF2. Furthermore, a red light-activated K1 kinase phosphorylated RopGEF2, suggesting that RopGEF2 was regulated by transcription and posttranslational modification. Based on these results, in this work, using the techniques of physiology, biochemistry and genetics, we will mainly investigate: transcriptional regulation of guard cell RopGEF2 by the key transcription factors in light signaling pathway; the dynamic changes of K1 activity under light, and the effect of K1 on RopGEF2 activity and stomatal movements; relationship between RopGEF2 phosphorylation, ubiquitination and its’ stability. Research in this work will reveal a mechanism for light to fine-tune the level and activity of RopGEF2 in guard cells to prevent excess stomatal opening, and will also enrich the regulatory network of stomtal movements.