Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611, USA.
Department of Chemistry, University of Florida, Gainesville, FL, 32611, USA.
New Phytol. 2021 Aug;231(4):1449-1461. doi: 10.1111/nph.17447. Epub 2021 Jun 10.
Two natural auxins, phenylacetic acid (PAA) and indole-3-acetic acid (IAA), play crucial roles in plant growth and development. One route of IAA biosynthesis uses the glucosinolate intermediate indole-3-acetaldoxime (IAOx) as a precursor, which is thought to occur only in glucosinolate-producing plants in Brassicales. A recent study showed that overproducing phenylacetaldoxime (PAOx) in Arabidopsis increases PAA production. However, it remains unknown whether this increased PAA resulted from hydrolysis of PAOx-derived benzyl glucosinolate or, like IAOx-derived IAA, is directly converted from PAOx. If glucosinolate hydrolysis is not required, aldoxime-derived auxin biosynthesis may occur beyond Brassicales. To better understand aldoxime-derived auxin biosynthesis, we conducted an isotope-labelled aldoxime feeding assay using an Arabidopsis glucosinolate-deficient mutant sur1 and maize, and transcriptomics analysis. Our study demonstrated that the conversion of PAOx to PAA does not require glucosinolates in Arabidopsis. Furthermore, maize produces PAA and IAA from PAOx and IAOx, respectively, indicating that aldoxime-derived auxin biosynthesis also occurs in maize. Considering that aldoxime production occurs widely in the plant kingdom, aldoxime-derived auxin biosynthesis is likely to be more widespread than originally believed. A genome-wide transcriptomics study using PAOx-overproduction plants identified complex metabolic networks among IAA, PAA, phenylpropanoid and tryptophan metabolism.
两种天然植物生长素，苯乙酸（PAA）和吲哚-3-乙酸（IAA），在植物生长和发育中起着至关重要的作用。IAA 生物合成的一条途径使用硫代葡萄糖苷中间体吲哚-3-乙肟（IAOx）作为前体，据认为这种前体仅存在于芸薹属植物的硫代葡萄糖苷产生植物中。最近的一项研究表明，在拟南芥中过度产生苯乙肟（PAOx）会增加 PAA 的产生。然而，目前尚不清楚这种增加的 PAA 是来自 PAOx 衍生的苄基硫代葡萄糖苷的水解，还是像 IAOx 衍生的 IAA 一样，直接从 PAOx 转化而来。如果不需要硫代葡萄糖苷水解，则可能在芸薹属以外的植物中发生 aldoxime 衍生的生长素生物合成。为了更好地理解 aldoxime 衍生的生长素生物合成，我们使用拟南芥硫代葡萄糖苷缺陷突变体 sur1 和玉米进行了同位素标记 aldoxime 喂养实验和转录组学分析。我们的研究表明，PAOx 转化为 PAA 在拟南芥中不需要硫代葡萄糖苷。此外，玉米分别从 PAOx 和 IAOx 产生 PAA 和 IAA，表明 aldoxime 衍生的生长素生物合成也发生在玉米中。考虑到 aldoxime 的产生在植物界广泛存在，aldoxime 衍生的生长素生物合成可能比最初认为的更为普遍。使用 PAOx 过表达植物进行的全基因组转录组学研究鉴定了 IAA、PAA、苯丙烷和色氨酸代谢之间的复杂代谢网络。
