Department of Genetics, University of Delhi South Campus, Benito Juarez Road, New Delhi 110021, India.
Res Microbiol. 2011 May;162(4):426-35. doi: 10.1016/j.resmic.2011.03.006. Epub 2011 Mar 23.
Pseudomonas fluorescens is an important biological component of agricultural soils that bestows a number of direct and indirect beneficial attributes to the plants. We analyzed the biocontrol strain P. fluorescens Psd for indole-3-acetic acid (IAA) biosynthesis and studied the effect of its consequent manipulation on its plant-growth-promoting (PGP) potential. While the indole pyruvic acid (IPyA) pathway commonly associated with PGP bacteria was lacking, the indole acetamide (IAM) pathway generally observed in phytopathogens was expressed in strain Psd. Overexpression of IAM pathway genes iaaM-iaaH, from Pseudomonas syringae subsp. savastanoi drastically increased IAA levels and showed a detrimental effect on sorghum root development. On the other hand, heterologous expression of the indole-3-pyruvate decarboxylase/phenylpyruvate decarboxylase gene (ipdC/ppdC) of the IPyA pathway from the PGP bacterium Azospirillum brasilense SM led to enhancement of the IAA level. A more favorable effect of this recombinant strain on sorghum root growth and development suggests that metabolic engineering could be used to generate strains with improved PGP function.
荧光假单胞菌是农业土壤中的重要生物组成部分，它赋予了植物许多直接和间接的有益特性。我们分析了生防菌株荧光假单胞菌 Psd 吲哚-3-乙酸（IAA）的生物合成，并研究了其操纵对其植物生长促进（PGP）潜力的影响。虽然与 PGP 细菌相关的吲哚丙酮酸（IPyA）途径缺乏，但在病原菌中普遍观察到的吲哚乙酰胺（IAM）途径在菌株 Psd 中表达。过表达来自丁香假单胞菌亚种 savastanoi 的 IAM 途径基因 iaaM-iaaH，大大增加了 IAA 水平，并对高粱根的发育产生了不利影响。另一方面，来自 PGP 细菌 Azospirillum brasilense SM 的吲哚-3-丙酮酸脱羧酶/苯丙酮酸脱羧酶基因（ipdC/ppdC）的异源表达增强了 IAA 水平。该重组菌株对高粱根生长和发育的更有利影响表明，代谢工程可用于产生具有改良 PGP 功能的菌株。
