Zhao Yunde, Hull Anna K, Gupta Neeru R, Goss Kendrick A, Alonso José, Ecker Joseph R, Normanly Jennifer, Chory Joanne, Celenza John L
Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.
Genes Dev. 2002 Dec 1;16(23):3100-12. doi: 10.1101/gad.1035402.
The plant hormone auxin regulates many aspects of plant growth and development. Although several auxin biosynthetic pathways have been proposed, none of these pathways has been precisely defined at the molecular level. Here we provide in planta evidence that the two Arabidopsis cytochrome P450s, CYP79B2 and CYP79B3, which convert tryptophan (Trp) to indole-3-acetaldoxime (IAOx) in vitro, are critical enzymes in auxin biosynthesis in vivo. IAOx is thus implicated as an important intermediate in auxin biosynthesis. Plants overexpressing CYP79B2 contain elevated levels of free auxin and display auxin overproduction phenotypes. Conversely, cyp79B2 cyp79B3 double mutants have reduced levels of IAA and show growth defects consistent with partial auxin deficiency. Together with previous work on YUCCA, a flavin monooxygenase also implicated in IAOx production, and nitrilases that convert indole-3-acetonitrile to auxin, this work provides a framework for further dissecting auxin biosynthetic pathways and their regulation.
植物激素生长素调控植物生长和发育的多个方面。尽管已提出了几种生长素生物合成途径，但这些途径在分子水平上均未得到精确界定。在此，我们提供了体内证据，证明拟南芥的两种细胞色素P450（CYP79B2和CYP79B3）在体外可将色氨酸（Trp）转化为吲哚 - 3 - 乙醛肟（IAOx），它们是体内生长素生物合成中的关键酶。因此，IAOx被认为是生长素生物合成中的重要中间体。过表达CYP79B2的植物含有较高水平的游离生长素，并表现出生长素过量产生的表型。相反，cyp79B2 cyp79B3双突变体的吲哚 - 3 - 乙酸（IAA）水平降低，并表现出与部分生长素缺乏一致的生长缺陷。结合之前关于同样参与IAOx生成的黄素单加氧酶YUCCA以及将吲哚 - 3 - 乙腈转化为生长素的腈水解酶的研究工作，这项研究为进一步剖析生长素生物合成途径及其调控提供了一个框架。
