Auxin Conjugation in Arabidopsis

9320120吲哚-3-乙酸（IAA）是一类被称为生长素的植物生长激素的主要天然成员。IAA参与了广泛的植物过程，包括细胞生长和分化，果实发育和衰老。在植物中，大多数IAA不是以游离酸的形式出现，而是通过酯键与各种糖结合，或通过酰胺键与氨基酸或肽结合，后一种形式的结合在大多数植物中更为普遍。生长素偶联物有几个作用，包括在萌发过程中使用的储存，IAA稳态，甚至组织靶向。各种证据表明，生长素偶联物只有在水解为游离生长素后才有活性。尽管生长素在植物中具有明显的重要性，并且具有更大的偶联生长素库的潜在意义，但对IAA偶联物的合成或降解的生物化学知之甚少，对分子生物学或遗传学的了解就更少了。在这个提议中，几种方法将被用于分离参与IAA结合代谢的基因。该实验室最近通过酵母互补策略分离出一种编码共轭水解活性的cDNA。本提案的主要重点是表征该活性在拟南芥中的结构，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其他共轭功能和代谢的研究也将继续进行。＊＊＊

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. ***