拟南芥IDDs转录因子亚家族介导干旱胁迫应答反应的机制研究

As plant-specific transcription factors, IDDs mediate various aspects of plant growth and development, such as seed germination, flowering and organ morphogenesis. However, the interplay between plant and environmental factors by IDDs remains to be elucidated. Recently, we found that idd14-1D, a gain-of-function mutant of IDD14, exhibits enhanced drought tolerance, ABA-induced stomatal closure and seed germination inhibition, whereas loss-of-function mutation of IDD14, IDD15 and IDD16 genes results in reduced drought tolerance, ABA-induced stomatal closure and seed germination inhibition. Following yeast two-hybrid screening (Y2H) and bimolecular fluorescence complementation (BiFC) indicate that these IDDs can interact with ARIA, ARED1/ABF2 and form hetero- or homodimers in nuclei. Furthermore, genetic analysis shows that the inactivation of ARIA reduce the high sensitivity of idd14-1D to ABA. These data suggest that IDDs may form a complex with the key ABA signaling molecules and positively regulates Arabidopsis drought response possibly through ABA signaling pathway. In this study, we will isolate the IDD complex components and dissect the molecular mechanisms of IDD-modulated drought response in plant using a combination of physiologic, genetic, biochemical, molecular and bioinformatics approaches.

植物特有转录因子IDD调控植物生长发育的多个生物学进程，但对其介导的植物与环境因子互作仍知之甚少。我们发现IDD14、IDD15和IDD16亚家族中功能获得型突变体idd14-1D具有增强的干旱耐受能力、ABA诱导气孔关闭和种子萌发抑制，而功能缺陷的三突变体则表现降低的干旱耐性、ABA诱导气孔关闭和种子萌发抑制；利用酵母双杂交（Y2H）文库筛选系统及烟草双分子荧光互补技术（BiFC）初步证明这三个IDDs均能与ARIA、ABA信号通路中关键分子AREB1/ABF2及IDDs成员之间存在蛋白互作；遗传互作分析发现ARIA功能缺失能够抑制idd14-1D对ABA的高敏感性。据此，我们推测IDDs可能形成一个功能复合体，通过ABA信号途径正向调控拟南芥干旱胁迫应答反应。拟利用生理学、遗传学、生物化学、分子生物学和生物信息学等方法，鉴定IDD复合体组分，阐明该复合体调控植物干旱应答反应的分子机理。

IDD转录因子介导植物生长发育的各个方面。我们之前报道了拟南芥IDD亚家族调节生长素的空间积累，从而调节器官形态发生和重力反应。然而，该亚家族是否在其他激素途径和应激反应中发挥调节作用仍有待确定。在这里，我们结合生理、生化、分子和遗传的方法来提供证据，证明亚家族成员IDD14与bZIP 型结合因子/AREB结合蛋白 (ABFs/AREBs)（ABA信号的关键调节因子）能够发生互作，在ABA介导的耐旱性中发挥协同作用。idd14-1D是IDD14的功能获得性突变体，表现出减少的叶片水分流失和提高的耐旱性，而功能缺失突变体idd14-1中IDD14的失活导致蒸腾增加和耐旱性降低。改变的 IDD14表达影响 ABA敏感性和ABA介导的气孔关闭。IDD14 可以与 ABF1-4 发生相互作用并随后促进它们的转录活性。此外，ABFs的异位表达和突变可以分别抑制和增强idd14-1突变体对干旱胁迫的敏感性。综上所述，我们的研究结果表明，IDD14 与ABF能够形成功能复合体并参与正向调节干旱胁迫反应，从而揭示了IDD14在ABA信号传导和植物干旱胁迫响应中的先前未知的作用。