NASA/NSF Collaborative Research: Molecular Genetic Analysis of Gravitropism in Arabidopsis

土壤重力是决定许多植物根和芽生长方向的主要环境信号之一。向地性反应包括对重力信号的感知、信号的传输以及重新定向生长的响应程序的执行。因此，向地性构成了植物的信号转导途径。已知这一途径依赖于植物激素生长素的运输和接收。本研究旨在鉴定和表征拟南芥中参与向地性反应的基因。已经分离出几个具有向地性缺陷的突变体。这里的重点是分析两个特别有前途的突变体，rgr1和rcn1。这些数据表明，RCN1基因编码一种磷酸蛋白磷酸酶，表明RCN1在向地性信号转导中具有特定作用；RGR1的作用仍然未知。将继续研究突变体的生理和遗传特征，以确定RGR1和RCN1基因的功能。野生型等位基因的分子克隆和鉴定将进一步确定这些作用。野生型克隆将通过农杆菌介导的稳定转化重新引入拟南芥，以测试突变表型的互补。稳定转化实验也将用于证明改变这些基因的正常表达模式的生物学效应。遗传和分子方法将用于阐明RGR1和RCN1基因相互作用以及与向地性相关的其他基因的相互作用。这项工作将为植物向地性的分子机制和生长素介导的信号转导提供新的见解。* * *

9416027 Soll Gravity is one of the primary environmental signals determining the orientation of root and shoot growth in many plant species. The gravitropic response involves perception of the gravity signal, transmission of the signal, and execution of a response program that re-orients growth. Thus gravitropism constitutes a plant signal transduction pathway. This pathway is known to depend on tranport and reception of the plant hormone auxin. This research is designed to identify and characterize genes involved in the gravitropic response in Arabidopsis thaliana. Several mutants with defects in gravitropism have already been isolated. The focus here will be on the anlysis of two especially promising mutants, rgr1 and rcn1. The data indicates that the RCN1 gene encodes a phosphoprotein phosphatase, suggesting a specific role for RCN1 in gravitropic signal transduction; the role of RGR1 remains unknown. Work will continue on physiological and genetic characterization of the mutants, to establish the functions of the RGR1 and RCN1 genes. Molecular cloning and characterization of wild-type alleles will further define these roles. Wild-type clones will be re-introduced into Arabidopsis by Agrobacterium-mediated stable transformation to test for complementation of mutant phenotypes. Stable transformation experiemtns also will be used to demonstrate the biological effects of altering the normal expression pattersn of these genes. Genetic and molecular approaches will be used to elucidate interactions of the RGR1 and RCN1 genes with each other and with other genes involved in gravitropism. This work will provide new insights into the molecular mechanisms of gravitropism and of auxin-mediated signal transduction in plants. ***