Seo M, Akaba S, Oritani T, Delarue M, Bellini C, Caboche M, Koshiba T
Department of Biology, Tokyo Metropolitan University, Japan.
Plant Physiol. 1998 Feb;116(2):687-93. doi: 10.1104/pp.116.2.687.
Aldehyde oxidase (AO; EC 1.2.3.1) activity was measured in seedlings of wild type or an auxin-overproducing mutant, superroot1 (sur1), of Arabidopsis thaliana. Activity staining for AO after native polyacrylamide gel electrophoresis separation of seedling extracts revealed that there were three major bands with AO activity (AO1-3) in wild-type and mutant seedlings. One of them (AO1) had a higher substrate preference for indole-3-aldehyde. This AO activity was significantly higher in sur1 mutant seedlings than in the wild type. The difference in activity was most apparent 7 d after germination, the same time required for the appearance of the remarkable sur1 phenotype, which includes epinastic cotyledons, elongated hypocotyls, and enhanced root development. Higher activity was observed in the root and hypocotyl region of the mutant seedlings. We also assayed the indole-3-acetaldehyde oxidase activity in extracts by high-performance liquid chromatography detection of indole-3-acetic acid (IAA). The activity was about 5 times higher in the extract of the sur1 seedlings, indicating that AO1 also has a substrate preference for abscisic aldehyde. Treatment of the wild-type seedlings with picloram or IAA caused no significant increase in AO1 activity. This result suggested that the higher activity of AO1 in sur1 mutant seedlings was not induced by IAA accumulation and, thus, strongly supports the possible role of AO1 in IAA biosynthesis in Arabidopsis seedlings.
在拟南芥野生型或生长素过量产生突变体superroot1（sur1）的幼苗中测定了醛氧化酶（AO；EC 1.2.3.1）活性。对幼苗提取物进行非变性聚丙烯酰胺凝胶电泳分离后，对AO进行活性染色，结果显示野生型和突变体幼苗中有三条具有AO活性的主要条带（AO1 - 3）。其中一条（AO1）对吲哚 - 3 - 醛具有更高的底物偏好性。该AO活性在sur1突变体幼苗中显著高于野生型。在萌发后7天，活性差异最为明显，这也是sur1显著表型出现所需的时间，其表型包括子叶偏上生长、下胚轴伸长和根系发育增强。在突变体幼苗的根和下胚轴区域观察到更高的活性。我们还通过高效液相色谱检测吲哚 - 3 - 乙酸（IAA）来测定提取物中的吲哚 - 3 - 乙醛氧化酶活性。sur1幼苗提取物中的活性约高5倍，表明AO1对脱落醛也具有底物偏好性。用毒莠定或IAA处理野生型幼苗不会导致AO1活性显著增加。这一结果表明，sur1突变体幼苗中AO1的较高活性不是由IAA积累诱导的，因此，有力地支持了AO1在拟南芥幼苗IAA生物合成中可能发挥的作用。
