ANALYSIS OF AUXIN SIGNAL TRANSDUCTION PATHWAYS

根的向重力反应包括根冠细胞感知“重力刺激”，将这种物理信息转化为生化信号，然后将其传递到膨胀区的细胞。这最终会导致根部的适当曲率响应。吲哚-3-乙酸(IAA)是高等植物生长素的主要形式，它直接参与植物对光、重力等刺激的定向反应，甚至是生长过程中的障碍，但其作用机制尚未阐明。携带EIR1突变等位基因的植物，编码一种质膜蛋白，其表型表明它是一个生长素外排泵，参与生长素从根尖到伸长区的运输。这些突变体的根很长，形成根毛的能力受损，而且根对光或重力不反应。这些突变体类似于在生长素运输抑制剂存在下生长的植物。这项建议的重点是：1)进一步鉴定Eir1p，这是参与根向重力反应的关键成分；2)确定影响EIR1泵活性的蛋白质。这些研究将提供关于以前未知的生长素信号通路参与重力反应的洞察力。

The gravitropic response of roots involves perception of the 'gravistimulus' by root-cap cells, transduction of this physical information into biochemical signals, followed by their transmission to cells in the expansion zone. This ultimately results in an appropriate curvature response of the root. Indole-3-acetic acid (IAA), the major form of auxins in higher plants, is directly involved in providing directionality to plants in response to stimuli such as light, gravity and even obstacles in the path of growth but its mechanism of action has not been elucidated. Plants bearing mutant alleles of EIR1, which encodes a plasma membrane protein, have phenotypes that suggest it is an auxin efflux pump involved in transport of auxin from the root tip to the elongation zone. These mutants have long roots with compromised ability to form root hairs and the roots do not respond to light or gravity. These mutants resemble plants grown in the presence of auxin transport inhibitors. The focus of this proposal is: 1) to further characterize Eir1p, a key component involved in the gravitropic response of roots; and 2) to identify proteins that affect activity of the EIR1 pump. These studies will provide insight regarding the previously uncharacterized auxin signaling pathway involved in the gravitronic response.