Modulators of the Abscisic Acid Core Signaling Pathway

地球人口的增加，加上碳排放量的增加，正在导致我们全球气候的变化，在我们的集体需求增长的同时威胁到农业。气候变化表现为严重的天气事件，从不同地区的变暖和干旱到大风暴和洪水。生长季节的严重干旱和谷物成熟过程中的过度潮湿相结合，可导致全世界每年数十亿美元的产量损失。更好地了解控制植物胁迫耐受性和生产力的遗传机制可以帮助我们创造或培育能够更好地抵御不利气候事件的植物。激素脱落酸（ABA）是压力信号的关键调节剂。在过去的七年中，出现了一个“核心ABA信号通路”，它将许多以前在遗传学上确定的ABA信号组分机械地联系起来。该提案解决了一组蛋白质的功能，这些蛋白质与该核心途径的多个中心组分直接相互作用，可能作为信号枢纽发挥作用。了解控制ABA反应的相互作用可能有助于确保世界未来的粮食安全。ABA核心信号传导途径的中心组分包括四个蛋白质家族：ABA受体的PYL/PYR/RCAR家族、蛋白磷酸酶（PP）2Cs的进化枝A家族、Snf相关激酶（SnRK）2家族和ABA反应元件结合碱性亮氨酸拉链（bZIP）类转录因子的ABI5/ABF/AREB进化枝。另一个家族，ABI Five结合蛋白（AFP），直接与bZIPs，PP2C和SnRK2相互作用，也显示与染色质修饰剂的相互作用。本项目将探讨这些相互作用的机制和意义，包括：（1）AFPs是否通过在低ABA浓度下螯合bZIPs而作为含ABA响应元件（ABRE）基因的转录阻遏物;（2）AFPs是否与TPL样辅阻遏物或其他染色质修饰蛋白相互作用，从而改变由bZIPs调控的组蛋白乙酰化和基因活性;以及3）AFP功能和定位是否受PP2Cs和SnRK2或其它激酶介导的磷酸化变化的调节。拟议的实验将测试AFP如何有助于反馈系统，允许植物在发育或应激诱导的ABA水平下降时恢复生长。此外，他们将解决一个家族的生物化学功能仍然只注释为未知功能的蛋白质。

Increases in the human population of the Earth, coupled with increased carbon emissions, are leading to changes in our global climate that threaten agriculture just as our collective demands grow. Climate change is manifest as severe weather events ranging from warming and drought to major storms and flooding in different regions. The combination of severe drought during growing seasons and excessive moisture during cereal grain maturation can lead to many billions of dollars in annual yield losses worldwide. A better understanding of the genetic mechanisms controlling plant stress tolerance and productivity could help us to create or breed plants that could better withstand unfavorable climate events. The hormone abscisic acid (ABA) is a key regulator of stress signaling. Within the last seven years a "core ABA signaling pathway" has emerged that mechanistically links many ABA signaling components that were previously identified genetically. This proposal addresses the function of a group of proteins that interact directly with multiple central components of this core pathway, possibly functioning as signaling hubs. Understanding the interactions controlling ABA responses could be instrumental for ensuring the world's future food security. The central components of the ABA core signaling pathway include four families of proteins: the PYL/PYR/RCAR family of ABA receptors, the clade A family of protein phosphatase (PP)2Cs, the Snf-Related Kinase (SnRK)2 family,and the ABI5/ABF/AREB clade of ABA response element binding basic leucine zipper (bZIP) class transcription factors. An additional family, the ABI Five binding Protein (AFP)s, interact directly with the bZIPs, PP2Cs and SnRK2s, and also show interactions with chromatin modifiers. This project will address the mechanisms and implications of these interactions by determining 1) whether AFPs act as transcriptional repressors of ABA response element (ABRE)-containing genes by sequestering bZIPs at low ABA concentrations; (2) whether AFPs interact with TPL-like co-repressor(s) or other chromatin modifying protein(s) to alter histone acetylation and activity of genes regulated by bZIPs; and 3) whether AFP function and localization is regulated by changes in phosphorylation mediated by PP2Cs and SnRK2s or other kinases. The proposed experiments will test how the AFPs contribute to a feedback system that permits plants to resume growth when developmentally or stress-induced ABA levels decline. In addition, they will address the biochemical function(s) of a family still annotated only as proteins of unknown function.