Regulation of Division and Elongation During Root Growth

细胞分裂和扩增是细胞发育的基本过程，但它们之间的关系却很少被研究。在一个发育中的器官中，不知道如何划分分裂和快速扩张的区域；人们也不知道伸长率和分裂率是如何协调的。根据初步数据，PI首先假设，分裂在快速扩张开始之前就结束了；第二，快速膨胀的突然发生是由质子外排和细胞膜的水导率同步上调引起的；第三，分裂和扩张是相互调节的，所以一个的变化会引起另一个成比例的变化。该提议的具体目的是检验这些假设。为了做到这一点，PI将使用植物根，因为它的线性组织，不确定的生长，和实验的可及性。PI开发了一种运动学方法来量化速度、相对伸长率和细胞分裂率的空间分布。速度、相对伸长率、细胞分裂率和选定离子通量的概况将根据影响根生长的条件和基因型进行量化，包括发育和水分亏缺。然后PI将扰动延伸和分割，并将量化测量参数的变化。支持或反驳这些假设将增加我们对高等植物基本生长过程的理解。

Cell division and expansion are fundamental processes, however the relationship between them has been little studied. In a developing organ, it is not understood how the zones of division and rapid expansion are delimited; nor is it understood how rates of elongation and division are coordinated. Based on preliminary data, the PI hypothesizes first, that division ends well before rapid expansion begins; second, that the abrupt onset of rapid expansion is caused by a synchronous up-regulation of proton efflux and hydraulic conductivity of cell membranes; and third, that division and expansion are regulated reciprocally, so that a change in one elicits a proportional change in the other. The specific aims of the proposal are to test these hypotheses. To do so, The PI will use the plant root because of its linear organization, indeterminate growth, and experimental accessibility. The PI developed a kinematic method to quantify the spatial profiles of velocity, relative elongation rate and cell division rate. Profiles of velocity, relative elongation rate, cell division rate, and fluxes of selected ions will be quantified for conditions and genotypes that affect root growth, including development and water deficit. The PI will then perturb elongation and division and will quantify how the measured parameters change. Supporting or refuting the hypotheses will increase our understanding of fundamental growth processes in higher plants.