Role of Pseudomonas putida Indoleacetic Acid in Development of the Host Plant Root System

Abstract

Many plant-associated bacteria synthesize the phytohormone indoleacetic acid (IAA). While IAA produced by phytopathogenic bacteria, mainly by the indoleacetamide pathway, has been implicated in the induction of plant tumors, it is not clear whether IAA synthesized by beneficial bacteria, usually via the indolepyruvic acid pathway, is involved in plant growth promotion. To determine whether bacterial IAA enhances root development in host plants, the ipdc gene that encodes indolepyruvate decarboxylase, a key enzyme in the indolepyruvic acid pathway, was isolated from the plant growth-promoting bacterium Pseudomonas putida GR12-2 and an IAA-deficient mutant constructed by insertional mutagenesis. The canola seedling primary roots from seeds treated with wild-type P. putida GR12-2 were on average 35 to 50% longer than the roots from seeds treated with the IAA-deficient mutant and the roots from uninoculated seeds. In addition, exposing mung bean cuttings to high levels of IAA by soaking them in a suspension of the wild-type strain stimulated the formation of many, very small, adventitious roots. Formation of fewer roots was stimulated by treatment with the IAA-deficient mutant. These results suggest that bacterial IAA plays a major role in the development of the host plant root system.

Plant growth promotion abilities and formulation of Bacillus megaterium strain B 388 (MTCC6521) isolated from a temperate Himalayan location

“…The broth was incubated for 24 h at 28ºC on a rotary shaker. IAA production was quantifi ed periodically [9].…”

Plant growth promoting traits of psychrotolerant bacteria: A boon for agriculture in hilly terrains

“…Plant growth promoting rhizobacteria produce phytohormones that can affect cell proliferation in the root architecture by over production of lateral roots and root hairs with a subsequent increase of nutrient and water uptake a) Indole-3 -acetic acid (IAA) production The auxin, indole-3-acetic acid is an important phytohormone produced by PGPB and treatment with auxin-producing rhizobacteria has been shown to increase the plant growth (19). Many bacterial species have been isolated from cold environmental capable of producing IAA at low temperature.…”

The potential of plant microbiota in reducing postharvest food loss

“…Many plant‐associated bacteria are able to produce plant hormone‐like metabolites, and the role of auxins, cytokinins and gibberellins produced by bacteria in plant growth regulation is well documented (e.g. Steenhoudt and Vanderleyden, 2000; Patten and Glick, 2002; Spaepen et al ., 2007; Ortíz‐Castro et al ., 2008; Cassán et al ., 2009; Lambrecht et al ., 2000). Slininger et al .…”