拟南芥ABO7通过调控PP2C抑制ABA信号途径的机理研究

The ABA signaling has been studied clearly recently in Arabidopsis, which contains three major components including ABA receptor(PYR), type 2C protein phosphatase(PP2C) and SNF1-related protein kinase2(SnRK2). In the absence of ABA,the PP2C binds to SnRK2 and inhibits its activity. When the level of ABA is enough to be sensed,the PYR binds ABA and interacts with PP2C to suppress the phosphatase activities, resulting the activation of the SnRK2 which can phosphoryalte membrane proteins or transcription factors to regualte downstream gene expression. As the important negative regulators in the ABA signaling , the molecular regulation of PP2Cs remains large unknowm . One novel drought-related mutant named abo7 (ABA overly sensitive7) was isolated by using a genetic screen for ABA sensitive mutants through the root-bending assay. abo7 is more sensitive to ABA in seed gernination and seedling growth, has smaller stomatal apertures and is more drought tolerant than wild type.abo7 shows the same size of leaves as wild type in normal conditions but closes stomata more quickly than wild type under ABA treatment.BiFC and Co-IP assays indicate that ABO7 may interact with PP2Cs which were important negative regulaters in ABA signaling.This study will focus on the molecular mechanism of ABO7 how to suppress ABA signaling by regulating PP2C phosohatases.

ABA信号途径在拟南芥中研究得比较清楚，ABA受体PYR结合ABA后与蛋白磷酸酶PP2C结合，促使其释放出有活性的蛋白激酶SnRK2，磷酸化细胞膜上的蛋白或细胞核中的转录因子去调控下游基因表达。PP2C作为一个负调因子，在ABA信号通路中非常重要，除了受PYR调控，是否还受其他蛋白调控，这方面的研究报道还很少。我们利用拟南芥(Col)幼苗生长对ABA不敏感的特点筛选得到一个ABA敏感突变体abo7，响应干旱胁迫。实验结果表明abo7幼苗生长和萌发变绿均对ABA敏感、抗旱、气孔开度小于野生型、ABA诱导的气孔关闭快于野生型；利用双分子荧光互补实验(BiFC)和蛋白质免疫共沉淀(Co-IP)实验发现ABO7能与PP2Cs(ABI1、ABI2、HAB1、HAB2、AHG1和AHG3)发生相互作用。我们正在深入研究该基因如何通过调控PP2Cs来抑制ABA信号途径。