Control of G2 and Transition to Endocycles in the Plant Cell Cycle

植物生长对农业至关重要，对传统农作物的产量和用于生物燃料的生物量的生产具有重要影响。在细胞水平上，植物的生长包括两个不同的过程：细胞分裂（产生新细胞）和细胞扩增（增加细胞大小）。在分裂过程中，细胞的DNA含量加倍，随后细胞分裂形成两个细胞，这一过程被称为有丝分裂细胞周期。在生长的细胞扩增阶段，许多植物细胞继续进行细胞周期的修改版本，其中DNA含量加倍，但细胞不分裂。在经济上具有重要意义的细胞类型的例子包括谷物胚乳、棉花纤维和豆科植物的固氮共生根瘤。此外，这一过程在豆科植物根瘤的细胞分化和固氮过程中起着重要作用，但对这种细胞周期的详细机制尚不清楚。一种蛋白质（称为SIM）已被确定为细胞分裂抑制剂，但允许DNA复制。该项目的目的是了解植物生长过程中SIM如何调节分裂和DNA复制之间的平衡。该项目还将在不同背景的研究生和本科生的教育中发挥作用，将测试电影作为课堂教学工具的有效性，包括学习课程内容和学生对科学的态度，并将培养本科生对生物科学的数学建模。SIAMESE （SIM）基因编码一种细胞周期蛋白依赖性激酶（CDK）抑制剂，可阻断有丝分裂而不阻断DNA复制。虽然SIM在植物从有丝分裂生长到内复制的过程中起着关键作用，但是植物G2/M过渡的控制是复杂的，关于内复制是如何建立的，以及SIM和相关蛋白在这一过程中的作用仍然存在许多问题。这项工作将结合分子遗传操作、活细胞成像和数学建模来测试关于SIM和相关SMR蛋白在有丝分裂/内循环转变中的作用的特定假设。本提案的具体目标是回答以下问题：是否可以结合数学建模，遗传和细胞生物学实验来创建G2/M向内环过渡期间抑制的连贯模型？SIM蛋白的降解是如何调控的？在正常的有丝分裂周期中，SIM或其他smr是否在控制G2进程中发挥作用？

Plant growth is crucial to agriculture, with important implications for yields of traditional agricultural crops and for production of biomass for biofuels. At the cellular level, plant growth involves two distinct processes, cell division, which produces new cells, and cell expansion, which increases the size of the cells. During division, the cell doubles its DNA content and subsequently the cell divides to form two cells, a process known as the mitotic cell cycle. During the cell expansion phase of growth, many plant cells continue a modified version of the cell cycle, in which the DNA content doubles but the cell does not divide. Examples of economically important cell types that double their DNA without division include cereal endosperm, cotton fibers, and nitrogen-fixing symbiotic nodules in legumes. In addition, this process plays important roles in cell differentiation, and is essential for nitrogen fixation in legume root nodules, but the detailed mechanism of this modified cell cycle remains poorly understood. A protein (known as SIM) has been identified that functions as an inhibitor of cell division, but allows DNA replication. The goal of this project is to understand how SIM regulates the balance between division and DNA replication during plant growth. The project will also play a role in the education of graduate students and undergraduates from diverse backgrounds, will test the effectiveness of the film as a classroom teaching tool, both in learning course content, and on student attitudes towards science, and will train undergraduates in mathematical modeling for the biological sciences.The SIAMESE (SIM) gene encodes a cyclin-dependent kinase (CDK) inhibitor that blocks mitosis without blocking DNA replication. Although SIM is clearly plays a key role in the transition from mitotic growth to endoreplication, the control of the G2/M transition in plants is complex, and many questions remain about how endoreplication is established, and the role of SIM and related proteins in this process. The proposed work will use a combination of molecular genetic manipulations, live cell imaging and mathematical modeling to test specific hypotheses about the role of SIM and the related SMR proteins in the mitosis/endocycle transition. The Specific Objectives of this proposal are to answer the following questions: Can a combination of mathematical modeling, genetic and cell biological experiments be used to create a coherent model of inhibition of G2/M during the transition to endocycles? How is degradation of SIM protein regulated? Do SIM or other SMRs play a role in controlling progression through G2 during the regular mitotic cycle?