Seo M, Peeters A J, Koiwai H, Oritani T, Marion-Poll A, Zeevaart J A, Koornneef M, Kamiya Y, Koshiba T
Department of Biological Sciences, Tokyo Metropolitan University, Hachioji-shi, Tokyo 192-0397, Japan.
Proc Natl Acad Sci U S A. 2000 Nov 7;97(23):12908-13. doi: 10.1073/pnas.220426197.
Abscisic acid (ABA) is a plant hormone involved in seed development and germination and in responses to various environmental stresses. The last step of ABA biosynthesis involves oxidation of abscisic aldehyde, and aldehyde oxidase (EC ) is thought to catalyze this reaction. An aldehyde oxidase isoform, AOdelta, encoded by AAO3, one of four Arabidopsis aldehyde oxidase genes (AAO1, AAO2, AAO3, and AAO4), is the most likely candidate for the enzyme, because it can efficiently catalyze the oxidation of abscisic aldehyde to ABA. Here, we report the isolation and characterization of an ABA-deficient Arabidopsis mutant that maps at the AAO3 locus. The mutant exhibits a wilty phenotype in rosette leaves, but seed dormancy is not affected. ABA levels were significantly reduced in the mutant leaves, explaining the wilty phenotype in rosettes, whereas the level in the mutant seeds was less reduced. No AOdelta activity could be detected in the rosette leaves of the mutant. Sequence data showed that the mutant contains a G to A substitution in the AAO3 gene. The mutation causes incorrect splicing of the ninth intron of AAO3 mRNA. We thus conclude that the ABA-deficient mutant is impaired in the AAO3 gene and that the gene product, AOdelta, is an aldehyde oxidase that catalyzes the last step of ABA biosynthesis in Arabidopsis, specifically in rosette leaves. Other aldehyde oxidases may be involved in ABA biosynthesis in other organs.
脱落酸（ABA）是一种植物激素，参与种子发育与萌发以及对各种环境胁迫的响应。ABA生物合成的最后一步涉及脱落醛的氧化，醛氧化酶（EC ）被认为催化此反应。由拟南芥四个醛氧化酶基因（AAO1、AAO2、AAO3和AAO4）之一的AAO3编码的醛氧化酶同工型AOdelta是该酶最有可能的候选者，因为它能有效地催化脱落醛氧化为ABA。在此，我们报道了一个定位于AAO3位点的ABA缺陷型拟南芥突变体的分离与鉴定。该突变体莲座叶呈现萎蔫表型，但种子休眠不受影响。突变体叶片中的ABA水平显著降低，这解释了莲座叶的萎蔫表型，而突变体种子中的ABA水平降低较少。在突变体的莲座叶中未检测到AOdelta活性。序列数据显示，该突变体的AAO3基因中存在一个从G到A的替换。该突变导致AAO3 mRNA第九个内含子的剪接错误。因此我们得出结论，ABA缺陷型突变体在AAO3基因上存在缺陷，并且该基因产物AOdelta是一种醛氧化酶，它催化拟南芥中ABA生物合成的最后一步，特别是在莲座叶中。其他醛氧化酶可能参与其他器官中的ABA生物合成。
