Abstract

Numerous studies have reported the stimulation of plant growth following inoculation with an IAA-producing PGPB. However, the specific mode of IAA production by the PGPB is rarely elucidated. In part, this is due to the overwhelming complexity of IAA biosynthesis and regulation. The promiscuity of the enzymes implicated in IAA biosynthesis adds another element of complexity when attempting to decipher their role in IAA biosynthesis. To date, the majority of research on IAA biosynthesis describes three separate pathways classified in terms of their intermediates—indole acetonitrile (IAN), indole acetamide (IAM), and indole pyruvic acid (IPA). Each of these pathways is mediated by a set of enzymes, many of which are traditionally assumed to exist for that specific catalytic role. This lends the possibility of missing other, novel, enzymes that may also incidentally serve that function. Some of these pathways are constitutively expressed, while others are inducible. Some enzymes involved in IAA biosynthesis are known to be regulated by IAA or by IAA precursors, as well as by a multitude of environmental cues. This review aims to provide an update to our current understanding of the biosynthesis and regulation of IAA in bacteria.

Key points

• IAA produced by PGPB improves bacterial stress tolerance and promotes plant growth.

• Bacterial IAA biosynthesis is convoluted; multiple interdependent pathways.

• Biosynthesis of IAA is regulated by IAA, IAA-precursors, and environmental factors.

中文翻译：

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吲哚-3-乙酸在植物相关细菌中的生物合成及其调控。

摘要

大量研究报告了接种产生IAA的PGPB可以刺激植物生长。但是，很少阐明PGPB生产IAA的具体方式。在某种程度上，这是由于IAA生物合成和调控的复杂性。试图破译它们在IAA生物合成中的作用时，涉及IAA生物合成的酶的混杂性增加了另一个复杂性。迄今为止，有关IAA生物合成的大多数研究都描述了按照其中间体分类的三种独立途径：吲哚乙腈（IAN），吲哚乙酰胺（IAM）和吲哚丙酮酸（IPA）。这些途径中的每一种均由一组酶介导，传统上认为其中许多酶是针对这种特定的催化作用而存在的。这可能会错过其他新颖的作品，可能还附带发挥功能的酶。这些途径中的一些是组成性表达的，而另一些是可诱导的。已知参与IAA生物合成的某些酶受IAA或IAA前体以及多种环境提示的调节。这篇综述旨在为我们目前对细菌中IAA的生物合成和调控的理解提供更新。

关键点

• PGPB生产的IAA改善了细菌的胁迫耐受性并促进了植物的生长。

•细菌IAA的生物合成令人费解；多种相互依赖的途径。

• IAA的生物合成受IAA，IAA前体调控，以及环境因素。