Regulation of Cell Proliferation during Plant Organ Morphogenesis

0091306鸟多细胞生物体的大小取决于细胞增殖和分化的发育程序的协调相互作用。 在高等植物中，器官的形成通过茎分生组织的持续活动而发生在整个生活史中。 由于植物细胞由于刚性细胞壁而缺乏运动性，因此细胞分裂和细胞扩张的时空模式被认为最终决定植物体的大小。 虽然驱动细胞分裂的细胞周期机制已在植物中被广泛研究，但对该机制在植物整体生长和发育的背景下如何起作用知之甚少。 这个建议的一个目标是阐明植物形态建成和细胞增殖之间的联系，通过研究细胞周期调节因子在指定器官细胞数量，因此器官大小的作用。Torii，Comai和Roberts博士已经确定了八个与哺乳动物细胞周期蛋白激酶抑制剂（CKI）p27 kip 1相似的拟南芥基因，该基因作为细胞周期的负调节因子。 初步分析的拟南芥CKIs（AtCKI）表明，mRNA抑制AtCKI的成熟器官的扩大，可能是由于扩大的芽分生组织和发育器官的分生能力的延迟停止。 本课题的研究目的是：（1）对AtCKI进行生物化学表征;（2）通过表征AtCKI水平改变的植物，分析细胞增殖与器官形成之间的关系;（3）研究不同AtCKI之间的功能冗余;（4）理解AtCKI介导的细胞增殖与表征的发育调控途径之间的相互作用。这些实验将为植物器官大小的发育机制提供新的见解，并确定细胞周期控制在植物器官发生中的作用。 此外，这项研究应该为通过基因操作设计理想的器官大小奠定基础。

0091306Torii Body size of multicellular organisms depends on the coordinated interplay of cell proliferation and differentiation of the developmental program. In higher plants, organ formation occurs throughout the life cycle by continual activity of the shoot meristem. Because plant cells lack motility due to rigid cell walls, spatio-temporal patterns of cell division and cell expansion are thought to ultimately determine plant body size. Although the cell cycle machinery that drives cell division has been extensively studied in plants, little is known about how the machinery acts in the context of growth and development of a plant as a whole. A goal of this proposal is to elucidate the connection between plant morphogenesis and cell proliferation by investigating roles of cell cycle regulators in specifying organ cell numbers, and therefore the organ size. Drs. Torii, Comai, and Roberts have identified eight Arabidopsis genes similar to the mammalian cyclin kinase inhibitor (CKI) p27kip1, which acts as a negative regulator of the cell cycle. Preliminary analyses of the Arabidopsis thaliana CKIs (AtCKI) suggested that mRNA suppression of the AtCKI causes enlargement of mature organs, presumably due to both an enlarged shoot meristem and delayed cessation of the meristematic competence of developing organs. The research in the present project period is intended to: (1) Biochemically characterize the AtCKI, (2) Analyze the relationship between cell proliferation and organogenesis by characterizing plants altered in the AtCKI levels, (3) Examine functional redundancy among different AtCKIs, and (4) Understand interplays between AtCKI-mediated cell proliferation and characterized developmental regulatory pathways. These experiments should provide a novel insight into developmental mechanism controlling plant organ size and define the roles for cell cycle control in plant organogenesis. Moreover, this research should lay the foundation for designing desirable organ sizes through genetic manipulation.