CAREER: Uncovering transcriptional regulatory mechanisms in plant thermomorphogenesis

在全球气候变化的背景下，植物面临着更加波动的温度环境。众所周知，热浪等极端温度对作物生产和生物多样性产生不利影响。然而，即使环境温度的小幅上升也会极大地改变各种植物物种的生长和发育。这些温度引起的器官生长速度的变化（例如，茎和根），生物量，开花时间，光合速率，水分利用效率，显著影响作物产量和适合度。然而，植物感知和响应适度增加的无压力（温暖）温度的精确机制仍然不清楚。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，创新的技术已被开发或改造，以检查时空功能和结构-功能关系的关键转录调控因子和它们的辅助因子在热敏生长。了解这些机制对于我们设计和培育气候适应性作物至关重要，可能会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下一代科学家，从高中到研究生，从事尖端研究。与极端温度引发的胁迫反应不同，植物对非胁迫环境温度波动的反应需要独特的机制。在所发现的成分中，热敏转录因子（TTFs）在温暖温度诱导的下胚轴（胚胎干）生长中发挥主要作用，这一过程称为热形态发生。在已鉴定的TTF家族中，PIF 4在调节热形态发生生长中起关键作用。温暖的温度通过一种未知的机制激活PIF 4转录，积累的PIF 4通过激活参与生长激素生长素生物合成和响应的关键基因来促进下胚轴生长。PI发现HEMERA（HMR）作为PIF 4的共激活因子激活温度响应基因表达。尽管HMR是PIF 4活性和蛋白质在温暖温度下稳定性所必需的，但如何实现这些调节仍然是难以捉摸的。通过正向和反向遗传方法和生物信息学分析，PI的研究小组已经确定了多种因素，这些因素可能会在温度升高时调节PIF 4的表达、活性和蛋白质稳定性。这项研究将揭示PIF 4介导的热形态发生机制以及PIF 4和其他TTF家族形成的转录调控网络。综合教育计划将提高干准备在密西西比和整个密西西比州的大学，并包括努力1）加强本科和研究生教育在植物分子遗传学和生理学在UM; 2）开发植物表型组学和分子遗传学夏季研究计划在UM和HBCU代表性不足的少数民族学生; 3）为高中和社区大学的弱势学生开发植物分子生物学暑期研究项目。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.