Role of the FEI/ACC pathway in regulating cell wall synthesis

植物细胞被一层主要由糖链构成的半硬墙所包围。这种植物细胞壁提供结构支撑，确定细胞的大小和形状，并为病原体的感染提供屏障。植物细胞壁是对发育和环境信号做出反应的多样性和高度动态的结构。植物细胞壁的主要承重成分是纤维素，它是由一种叫做纤维素合成酶的大型酶复合体在细胞表面制造的。在这个项目中，它将描述植物如何调节它们产生多少纤维素。先前的工作揭示了一条通过调节纤维素合成酶复合体到细胞表面的运动来控制这一过程的途径。这条途径是如何工作的，以及它是如何与细胞中的其他元素相互作用来控制纤维素合成酶的，我们将进行探索。此外，还发现了一种新的信号分子1-氨基环丙烷-1-羧酸(ACC)，它是乙烯的前体，在该途径中起作用。将确定ACC是如何被细胞感知的，以及它如何作用于调节纤维素合成酶的功能。这项工作的结果将为深入了解植物如何调节细胞壁的生物合成提供洞察力，这对于理解植物形态的发展和其他过程至关重要，对新兴的生物燃料行业也很重要。该项目将与旨在增加少数群体在科学界的代表性的项目和几个旨在增加公众对植物科学的理解的外展项目相互作用。已经定义了调节细胞壁合成的信号途径，其中包括FEI受体样激酶、SHOU4(一种新的跨膜蛋白)和ACC作为独立于其转化为乙烯的信号。以往的研究结果表明，该途径通过调节CESA(纤维素合酶)向质膜的转运来调节CESA的功能。为了进一步阐明这一途径是如何调控CESA功能的，提出了一系列不同的补充实验。将被检验的一个主要假设是，SHOU4在PM充当CESA水平的计数器，该复合体产生一个信号，负向调节CESA的胞吐作用，以维持纤维素生物合成的最佳水平。这个模型的一个关键方面是SHOU4和CESA的直接相互作用。这种相互作用将被进一步表征，包括阐明磷酸化的作用，可能是通过FEI激酶。该复合体的输出将通过筛选与SHOU4相互作用的蛋白质来鉴定。将被检验的第二个假说是ACC负向调节CESA功能。基因筛查被用来识别与ACC感知有关的元素。这些突变株系将被进一步鉴定，与这些突变相对应的基因将被克隆和鉴定。这些研究将增加对细胞壁生物合成如何受到调控的理解，这一过程对植物生长和发育的许多方面都是核心的，对新兴的生物燃料行业也很重要。此外，这些研究将开始定义植物ACC功能的潜在机制。该奖项由整合组织系统部门的生理机制和生物力学项目以及分子和细胞生物科学部门的细胞动力学和功能集群共同资助。该奖项反映了NSF的法定使命，并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，被认为值得支持。

Plant cells are surrounded by a semi-rigid wall that is made primarily of chains of sugars. This plant cell wall provides structural support, defines the size and shape of cells, and provides a barrier to infection by pathogens. Plant cell walls are diverse and highly dynamic structures that respond to developmental and environmental cues. The main load-bearing component of plant cell walls is cellulose, which is made at the surface of cells by a large enzyme complex called cellulose synthase. In this project, it will be characterized how plants regulate how much cellulose they make. Prior work uncovered a pathway that controls this process by modulating the movement of the cellulose synthase complex to the cell surface. How this pathway works and how it interacts with the other elements in the cell to control cellulose synthase will be explored. Further, a novel signaling molecule, 1-aminocyclopropane-1-carboxylic acid (ACC), a precursor to ethylene, was found to act in this pathway. How ACC is perceived by cells and how it acts to modulate cellulose synthase function will be determined. The results from this work will provide insight into how plants regulate cell wall biosynthesis, which is crucial to understanding the development of plant form and other processes and is important for the burgeoning biofuels industry. This project will interact with programs designed to increase the representation of minorities in the sciences and several outreach programs that aim to increase the public understanding of plant science.A signaling pathway regulating cell wall synthesis has been defined that includes the FEI receptor-like kinases, SHOU4 (a novel transmembrane protein), and ACC acting as a signal independent of its conversion to ethylene. Prior results suggest that this pathway regulates CESA (cellulose synthase) function by modulating CESA trafficking to the plasma membrane. A diverse set of complementary experiments are proposed to further elucidate how this pathway regulates CESA function. A primary hypothesis that will be tested is that SHOU4 acts as a counter of CESA levels at the PM, with the complex generating a signal to negatively regulate CESA exocytosis to maintain optimal levels of cellulose biosynthesis. One key aspect of this model is the direct interaction of SHOU4 and CESA. This interaction will be further characterized, including elucidating the role of phosphorylation, potentially by the FEI kinases. Outputs of this complex will be identified by screening for proteins that interact with SHOU4. A second hypothesis that will be tested is that ACC negatively regulates CESA function. A genetic screen was used to identify elements involved in ACC perception. These mutant lines will be further characterized and the genes corresponding to these mutations will be cloned and characterized. These studies will increase the understanding of how cell wall biosynthesis is regulated, a process that is central to many aspects of plant growth and development and which is important for the burgeoning biofuels industry. Further, these studies will begin to define the mechanisms underlying ACC function in plants.This award was co-funded by the Physiological Mechanisms and Biomechanics Program in the Division of Integrative Organismal Systems and the Cellular Dynamics and Function Cluster in the Division of Molecular and Cellular Biosciences.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.