Analysis of Function and Agricultural Application of Plant Aldehyde oxidase using Transgenic Plants

醛氧化酶(AO)在动物和微生物中得到了广泛的研究。然而，在植物中，关于这种酶的信息有限。该酶可能参与吲哚-3-乙酸(IAA)和脱落酸(ABA)的生物合成，引起了人们的极大兴趣。在本研究中，我们从拟南芥中克隆了四个全长的AO基因，并利用含有这些基因的转基因植物研究了它们的生理功能。我们还试图将这些结果推广到农业应用上。(1)从拟南芥中获得了四个不同的AO基因克隆。将这4个AO基因分别导入巴斯德毕赤酵母中，并在酵母细胞中进行功能表达。结果表明，在拟南芥幼苗中，两个AO基因编码3个AO，另一个AO基因产生一个叶AO。利用酵母表达的AOS进行的生化研究表明，苗期的AO可能参与了IAA的生物合成，而叶片的AO最有可能是催化脱落醛氧化形成ABA的AO的候选基因。(3)将4个AO克隆导入拟南芥，获得了各自的高表达和抑制株系。(4)我们还成功地筛选了几个含有这些基因的基因敲除株系。

Aldehyde oxidase (AO) has been extensively investigated in animals and microorganisms. In plants, however, there was only a limited information on this enzyme. A great interest in this enzyme has been in its possible involvement in indole-3-acetic acid (IAA) and abscisic acid (ABA) biosynthesis. In the present study, we cloned four full-length AO cDNAs from Arabidopsis thaliana and investigate their physiological functions using transgenic plants with these genes. We also tried to develop these results to agricultural application.(1) Four different putative AO cDNA clones were obtained from A. thaliana. Their products were analyzed by using antibodies each specific to four AOs in A. thaliana.(2) The four AO cDNAs were introduced into yeast Pichia pastoris and the products were functionally expressed in the yeast cells. The result revealed that two AO genes encoded three AOs in A. thaliana seedlings and another AO gene produced a leaf AO. Biochemical studies using AOs expressed in yeast indicated that one of seedling AO might be involved in IAA biosynthesis and a leaf AO is a most possible candidate of an AO that catalyzes oxidation of abscisic aldehyde to form ABA.(3) The four AO cDNA clones were introduced into A. thaliana and some over expressed and suppressed lines were obtained for each DNA construct.(4) We also succeeded screening several knockout lines with these genes.