CAREER: Uncovering transcriptional regulatory mechanisms in plant thermomorphogenesis

在全球气候变化的背景下，植物面临着更加多变的温度环境。众所周知，热浪等极端温度对作物生产和生物多样性有不利影响。然而，环境温度即使稍有上升，也会极大地改变各种植物的生长和发育。这些温度引起的器官(如茎和根)的生长速度、生物量、开花时间、光合作用速率和水分利用效率的变化，显著影响作物的产量和适合性。然而，植物感知和响应适度升高的、无压力(温暖)温度的确切机制仍然不清楚。拟议项目的长期目标是阐明温暖温度触发关键基因表达的调控机制，这些基因的产物有助于陆地植物的形态和结构变化。为了实现这一目标，人们开发或采用了创新技术来研究关键转录调控因子及其在热敏生长中的辅助因子的时空功能和结构-功能关系。了解这些机制对于我们设计和培育适应气候变化的作物至关重要，有可能减少全球变暖对作物生产力和粮食安全的不利影响。该项目的成功还将有助于培养从高中到研究生水平的下一代科学家进行尖端研究。与极端温度引发的应激反应不同，植物对非应激环境温度波动的反应需要独特的机械。在已发现的组分中，热敏转录因子(TTF)在温度诱导的下胚轴(胚茎)生长过程中起主要作用，这一过程被称为热形态发生。在已鉴定的TTF家族中，PIF4在调节热形态发生生长中起着关键作用。温暖的温度通过一种未知的机制激活PIF4的转录，积累的PIF4通过激活与生长激素生长素的生物合成和反应有关的关键基因来促进下胚轴的生长。PI发现HMERA(HMR)是PIF4在激活热反应基因表达方面的辅助激活剂。尽管HMR是PIF4活性和蛋白质在温暖温度下稳定所必需的，但这些调节是如何实现的仍然难以捉摸。通过正向和反向遗传方法和生物信息学分析，Pi的团队已经确定了多种因素，这些因素可能调节PIF4的表达、活性和蛋白质在温度升高时的稳定性。这项拟议的研究将揭示PIF4介导的热形态发生机制和由PIF4和其他TTF家族形成的转录调控网络。综合教育计划将改善密西西比大学和密西西比州的STEM准备，包括努力1)加强密歇根大学植物分子遗传学和生理学的本科生和研究生教育；2)为密歇根大学和HBCU代表不足的少数族裔学生制定植物表现学和分子遗传学暑期研究计划；3)为贫困背景的高中和社区大学生制定植物分子生物学暑期研究计划。该奖项反映了NSF的法定使命，通过使用基金会的智力优势和更广泛的影响审查标准进行评估，认为值得支持。

In the context of global climate change, plants face a more fluctuating temperature environment. It is well known that extreme temperatures such as heatwaves have detrimental impacts on crop production and biodiversity. However, even smaller increases in ambient temperatures would dramatically change the growth and development of various plant species. These temperature-induced changes in the growth speed of organs (e.g., stem and roots), biomass, flowering time, the rate of photosynthesis, and the efficiency of water usage, significant impact crop yield and fitness. However, the precise mechanisms by which plants sense and respond to moderately increased, nonstressful (warm) temperatures are still unclear. The long-term goal of the proposed project is to elucidate the regulatory mechanisms by which warm temperatures trigger the expression of critical genes whose products contribute to the morphological and architectural changes in land plants. To achieve this goal, innovative technologies have been developed or adapted to examine the spatiotemporal functions and structure-function relationships of critical transcriptional regulators and their co-factors in thermosensory growth. Understanding these mechanisms is crucial for us to design and breed climate-resilient crops, potentially reducing the adverse effects of global warming on crop productivity and food security. The success of the project will also help train next-generation scientists from high school to graduate levels in performing cutting-edge research. Different from the stress responses triggered by extreme temperatures, plant responses to nonstressful ambient temperature fluctuations require unique machinery. Among the discovered components, thermosensory transcription factors (TTFs) play primary roles in warm-temperature-induced hypocotyl (embryonic stem) growth, a process termed thermomorphogenesis. Among the identified TTF families, PIF4 plays a pivotal role in modulating thermomorphogenetic growth. Warm temperatures activate PIF4 transcription through a yet unknown mechanism, and accumulated PIF4 promotes hypocotyl growth by activating key genes involved in the biosynthesis of and response to the growth hormone auxin. The PI discovered HEMERA (HMR) as a coactivator of PIF4 in activating the thermoresponsive gene expression. Although HMR is required for PIF4 activity and protein stability at warm temperatures, how these regulations are achieved remains elusive. Through forward and reverse genetic approaches and bioinformatic analyses, the PI’s group has identified multiple factors that may regulate PIF4 expression, activity, and protein stability upon temperature elevations. The proposed research will uncover PIF4-mediated thermomorphogenetic mechanisms and transcriptional regulatory networks formed by PIF4 and other TTF families. The integrated educational plan will improve STEM preparedness at the University of Mississippi and across the state of Mississippi and includes efforts to 1) enhance undergraduate and graduate education in plant molecular genetics and physiology at UM; 2) develop a plant phenomics and molecular genetics summer research program for underrepresented minority students at UM and HBCUs; 3) develop a plant molecular biology summer research program for high school and community college students with disadvantaged backgrounds.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.