Regulation of Division and Elongation During Root Growth

细胞分裂和扩张是细胞的基本过程，但对它们之间的关系研究甚少。在一个发展中的器官中，人们不知道如何划分分裂和快速扩张的区域，也不知道伸长和分裂的速度是如何协调的。根据初步数据，PI假设：第一，分裂在快速扩张开始之前就结束了；第二，快速扩张的突然开始是由质子外流和细胞膜的水力传导性同步上调引起的；第三，分裂和扩张是相互调节的，因此一个分裂的变化会引起另一个分裂的比例变化。该提案的具体目的是检验这些假说。为了做到这一点，PI将使用植物的根，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、相对延伸率和细胞分裂率的空间分布。选择离子的速度、相对伸长率、细胞分裂率和通量的分布将被量化，以确定影响根生长的条件和基因类型，包括发育和水分亏缺。PI将扰乱伸长和分裂，并将量化测量参数的变化。支持或驳斥这些假说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.