9407617 Bandurski This investigator has cloned and sequenced a gene for the enzyme catalyzing the reaction: IAA+UDPG 1-0-IAA-glucose+UDP. This gene is important because the synthesis of IAA-glucose is the first step in the biosynthesis of the conjugates of indole-3-acetic acid (IAA) in Zea mays and because this is the first higher plant gene of IAA metabolism to be cloned and sequenced. Homologous sequences are present in Arabidopsis and tobacco and in all the monocotyledonous and dicotyledonous plants tested to date. The overall goal of this work is to control the size of the endogenous pools of the plant growth hormone, indole-3-acetic acid (IAA, auxin), by genetic means. All plants examined contain most of their IAA in a conjugated, and presumably, inactive form. It is the free acid which appears to be the active hormone. The ability to regulate the concentrations of free, versus conjugated, growth hormone levels, will be of value in understanding how IAA levels are regulated in plants; will possible provide information concerning how the tip of the shoot regulates shoot elongation; and will be of possible agronomic value in promoting or reducing plant growth without application of growth-regulating chemicals. During this granting period, the cDNA and genomic homologs of the corn cDNA encoding for IAGlu synthetase will be identifed and sequenced from Arabidopsis or tobacco; transgenic Arabidopsis and/or tobacco plants will be constructed with the IAGIu synthetase gene placed under a promoter in an antisense orientation to block expression of mRNA involved in synthesis of IAGlu synthetase; reported gene constructs will be prepared in Arabidopsis to study the time and localization of expression of the IAGlu synthetase gene; and, two different cDNA clones believed to encode genes controlling hydrolysis of 1-0-IAGlu and 6-0-IAGlu will be sequenced and their enzymatic activity characterized in an E. coli expression system. ***
