Auxin Conjugation in Arabidopsis

9320120吲哚-3-乙酸（IAA）是一类称为生长素的植物生长激素的主要天然成员。 IAA参与植物细胞生长和分化、果实发育和衰老等多种过程。 在植物中，大多数IAA不是以游离酸的形式存在，而是通过酯键与各种糖缀合或通过酰胺键与氨基酸或肽缀合，后一种形式的缀合物在大多数双子叶植物中更普遍。 生长素结合物的几种作用已经被假定，包括在发芽期间使用的储存、IAA体内平衡，甚至组织靶向。 各种证据表明，生长素缀合物只有在水解成游离生长素后才有活性。 尽管生长素在植物中的明显重要性，以及共轭生长素的更大储存库的潜在意义，但对IAA共轭物的合成或降解的生物化学知之甚少，甚至对分子生物学或遗传学知之甚少。 在这个建议中，几种方法将被用来分离基因参与IAA共轭代谢。 本实验室最近通过酵母互补策略分离了编码缀合物水解活性的cDNA。 这项建议的主要重点是表征拟南芥中这种活性的结构，表达和生物学功能的许多方面。 如果时间允许，在cDNA分离之前正在进行的关于结合物功能和代谢的其他研究也将继续进行。 ***

9320120 Town Indole-3-acetic acid (IAA) is the principal naturally-occurring member of a class of plant growth hormones known as auxins. IAA is involved in a wide range of plant processes including cell growth and differentiation, fruit development and senescence. In plants, most of the IAA occurs not as the free acid, but conjugated either to various sugars via ester linkages or to amino acids or peptides via amide bonds, the latter form of conjugate being more prevalent in most dicots. Several roles have been postulated for auxin conjugates, including storage for use during germination, IAA homeostasis, and even tissue targeting. Various lines of evidence suggest that auxin conjugates are active only after hydrolysis to free auxin. Despite the obvious importance of auxin in the plant, and the potential significance of the much larger reservoir of conjugated auxin, very little is known about the biochemistry and even less about the molecular biology or genetics of the synthesis or degradation of IAA conjugates. In this proposal, several approaches will be used to isolate genes involved in IAA conjugate metabolism. This laboratory has recently isolated a cDNA encoding a conjugate hydrolyzing activity by a yeast complementation strategy. The principal focus of this proposal is to characterize many facets of the structure, expression and biological function of this activity in Arabidopsis. As time permits, other studies on conjugate function and metabolism which were ongoing prior to the cDNA isolation will also be continued. ***