ANALYSIS OF AUXIN SIGNAL TRANSDUCTION PATHWAYS

根的向地性反应包括根冠细胞对“重力刺激”的感知，将这种物理信息转导成生化信号，然后将其传递给膨胀区的细胞。这最终导致根的适当曲率响应。吲哚-3-乙酸（IAA）是高等植物生长素的主要形式，直接参与植物在生长过程中对光、重力甚至障碍物等刺激提供方向性，但其作用机制尚未阐明。携带编码质膜蛋白的EIR1突变等位基因的植物，其表型表明它是一个生长素外流泵，参与生长素从根尖运输到伸长区。这些突变体有长根，形成根毛的能力受损，根对光或重力没有反应。这些突变体类似于生长在生长素运输抑制剂存在下的植物。本文的研究重点是：1)进一步研究参与根系向地性响应的关键组分Eir1p；2)鉴定影响EIR1泵活性的蛋白。这些研究将提供关于以前未被表征的生长素信号通路参与重力反应的见解。

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.