Function of Basic Helix-Loop-Helix Transcription Factors in Specifying Stomatal Cell Fate

陆地植物的生产力依赖于气孔的正确发育和功能，气孔是植物表面的微型阀。气孔调节植物和大气之间的气体运动。二氧化碳分子(一种温室气体)通过气孔进入植物，并通过光合作用转化为碳水化合物。氧气是光合作用的副产品，然后通过气孔从植物释放到大气中。此外，通过开放气孔的水分损失，这一过程被称为蒸腾作用，促进水分从根部移动，支持植物生长，而关闭气孔则防止植物枯萎。在植物发育过程中，气孔是通过一系列分化事件形成的，其中具有基本螺旋-环-螺旋(BHLH)基序的“主调控”转录因子的激活起着关键作用。三个bHLH蛋白，无言语、静音和FAMA，在气孔细胞分化的连续三个步骤中起开关作用，另外两个bHLH蛋白，Scream(SCRM)/ICE1和SCRM2，通过形成异源二聚体作为它们的伙伴。尖叫因子的活性决定了植物表皮的命运：完全没有尖叫会导致气孔细胞谱系的消失，而SCRM/ICE1功能的获得则会导致植物被气孔覆盖。本研究项目将揭示SCRM/ICE1及其类似蛋白在决定气孔细胞命运中的功能和调控，并研究SCRM/ICE1如何影响气孔特异的bHLH蛋白。抑制它们活动的生化机制将被研究，调节它们活动和功能的新因素将使用敏感的基因筛查被分离出来。SCRM/ICE1在耐寒性和气孔分化中具有双重作用，其双重作用的机制有待进一步探讨。该项目的更广泛影响包括培训年轻的女科学家(一名初级博士后研究员和一名研究生)和一名本科生，她们将有极好的机会获得植物发育生物学、分子遗传学、生物化学和细胞成像方面的广泛培训。更多的本科生研究人员也将通过独立研究来获得学分。他们将直接由PI指导制定科学假设，解释他们的结果，并在实验室内和公开场合展示他们的发现。这个项目的一部分将被纳入生物学入门课堂(招生人数超过200人)，并纳入大学二年级和三年级的实践实验室体验。将开展外展讲座，强调植物气孔与人类生活之间的联系，并鼓励年轻女科学家在职业道路上取得进步。

The productivity of land plants relies on the proper development and function of stomata, which are microscopic valves on the plant surface. Stomata regulate the movement of gases between plants and the atmosphere. Molecules of carbon dioxide (a greenhouse gas) enter the plant through the stomata and are converted into carbohydrates by photosynthesis. Oxygen, a byproduct of photosynthesis, is then released from plants to the atmosphere through the stomata. In addition, water loss through open stomata, a process known as transpiration, promotes water movement from the roots and supports plant growth, while closure of stomata prevents plants from wilting. During plant development, stomata are formed through a series of differentiation events, where activation of "master regulatory" transcription factors with a basic helix-loop-helix (bHLH) motif play a pivotal role. Three bHLH proteins, SPEECHLESS, MUTE, and FAMA, act as a switch for three consecutive steps of stomatal cell differentiation, and two other bHLH proteins, SCREAM (SCRM)/ICE1 and SCRM2, act as their partners through the formation of heterodimers. The activity of the SCREAM factors determines the fate of the plant epidermis: the complete absence of SCREAMs eliminates stomatal cell lineages, while gain-of-function of SCRM/ICE1 results in plants that are covered with stomata. This research project will uncover the function and regulation of SCRM/ICE1 and its paralog in specifying stomatal cell fate, and investigate how SCRM/ICE1 influence stomatal-specific bHLH proteins. Biochemical mechanisms that inhibit their action will be investigated, and novel factors that regulate their activity and function will be isolated using a sensitive genetic screen. SCRM/ICE1 has a dual role in freezing tolerance and stomatal differentiation, and the mechanism of the dual function will be explored. The broader impacts of this project include the training of young female scientists (a starting postdoctoral fellow and a graduate student) and an undergraduate student, who will have excellent opportunities to obtain broad training in plant developmental biology, molecular genetics, biochemistry, and cell imaging. Additional undergraduate researchers will also be trained through independent research for credit. They will be mentored directly by the PI to formulate scientific hypotheses, interpret their results, and present their findings within the laboratory as well as in a public setting. A part of this project will be incorporated into the Introductory Biology classroom (with an enrollment of greater than 200 students) and into practical laboratory experiences for college sophomores and juniors. Outreach lectures will be initiated to emphasize the connections between plant stomata and human life, and to encourage young female scientists to advance in their career paths.