Cell Differentiation and the Plant Cell Cycle

在多细胞生物的发育过程中，细胞分化与细胞分裂密切协调。在动物中，失去对细胞分裂的控制会导致癌症。在植物和动物的分化中，一些细胞类型表现出修改的细胞分裂周期，其中DNA被复制而不伴随细胞分裂，从而增加了核DNA含量。这被称为内复制；在植物中，内复制细胞类型的重要例子包括谷类胚乳、棉纤维和豆类植物中的固氮共生根瘤。虽然已知内复制在这些关键系统中很重要，但其详细的机制和调控仍然知之甚少。以前使用拟南芥叶毛(毛状体)作为细胞分化模型的工作表明，暹罗(Siamese，SIM)基因编码一种细胞周期蛋白依赖的激酶抑制剂，在内复制建立过程中抑制有丝分裂，并定义了一个暹罗相关(SMR)基因家族，该基因家族存在于所有陆地植物基因组中，功能相似。该项目的目的是更好地确定SIM蛋白抑制细胞分裂的生化机制，检验关于SIM蛋白本身如何调控的假说，并调查一些SMR基因在植物生长和发育中的作用。通过阐明内部复制以及细胞分裂和细胞分化的协调机制，该项目将促进对植物生长和发育的理解，这些生长和发育与改良传统作物和生产生物燃料用生物质有关。此外，比较植物和动物的细胞周期控制机制可能会提供与人类疾病相关的有用的见解。最后，计划的工作将在不同背景的研究生、本科生和高中生的教育中发挥作用。

During the development of multicellular organisms, cell differentiation is tightly coordinated with cell division. In animals, loss of control of cell division leads to cancer. In both plant and animal differentiation, some cell types display a modified cell division cycle where the DNA is replicated without concomitant cell division, thus, increasing nuclear DNA content. This is called endoreplication; in plants, important examples of endoreplicated cell types include cereal endosperm, cotton fibers, and nitrogen-fixing symbiotic nodules in legumes. Although endoreplication is known to be important in these critical systems, its detailed mechanism and regulation remain poorly understood. Previous work using Arabidopsis leaf hairs (trichomes) as a model for cell differentiation demonstrated that the SIAMESE (SIM) gene encodes a cyclin-dependant kinase inhibitor that suppresses mitosis during establishment of endoreplication, and defined a gene family of SIAMESE-RELATED (SMR) genes found in all land plant genomes that may function similarly. The project aims are to better define the biochemical mechanisms through which the SIM protein inhibits cell division, to test hypotheses about how the SIM protein itself is regulated, and to investigate the roles of some of the SMR genes in plant growth and development. By illuminating the mechanisms underlying endoreplication and the coordination of cell division and cell differentiation, the project will advance the understanding of plant growth and development relevant to improvement of both traditional crops and production of biomass for biofuels. Additionally, comparison of plant and animal cell cycle control mechanisms may give useful insights relevant to human disease. Finally, the projected work will play a role in the education of graduate students, undergraduates, and high school students from diverse backgrounds.