Production and Metabolism of Indole Acetic Acid in Root Nodules and Symbiont (Rhizobium undicola) Isolated from Root Nodule of Aquatic Medicinal LegumeNeptunia oleraceaLour.

Abstract

Indole acetic acid is a phytohormone which plays a vital role in plant growth and development. The purpose of this study was to shed some light on the production of IAA in roots, nodules, and symbionts of an aquatic legume Neptunia oleracea and its possible role in nodular symbiosis. The symbiont (N37) was isolated from nodules of this plant and identified as Rhizobium undicola based on biochemical characteristics, 16S rDNA sequence homology, and DNA-DNA hybridization results. The root nodules were found to contain more IAA and tryptophan than root; however, no detectable amount of IAA was found in root. The IAA metabolizing enzymes IAA oxidase, IAA peroxidase (E.C.1.11.1.7), and polyphenol oxidase (E.C.1.14.18.1) were higher in root than nodule but total phenol and IAA content were reversed. The strain N37 was found to produce copious amount of IAA in YEM broth medium with tryptophan and reached its stationary phase at 20 h. An enrichment of the medium with mannitol, ammonium sulphate, B12, and 4-hydroxybenzaldehyde was found to promote the IAA production. The presence of IAA metabolizing enzymes and IAA production with PGPR traits including ACC deaminase activity of the symbionts was essential for plant microbe interaction and nodule function.

Bacteria-Inducing Legume Nodules Involved in the Improvement of Plant Growth, Health and Nutrition

“…The production of aminocyclopropane-1-carboxylate (ACC) deaminase, responsible for the cleavage of the ethylene precursor ACC into ammonia and α-ketobutyrate, has been reported in different species of rhizobia from different genera (Nascimento et al 2014(Nascimento et al , 2018, such as Rhizobium (Ma et al 2003;Duan et al 2009), Allorhizobium (Ghosh et al 2015), Ensifer (formerly Sinorhizobium) (Ma et al 2004;Kong et al 2015), Mesorhizobium (Nascimento et al 2012) and Bradyrhizobium (Rangel et al 2017), and in nodulating species of Methylobacterium (Ekimova et al 2018).…”

“…Different genera of rhizobia have been reported to produce siderophores (Carson et al 2000;García-Fraile et al 2012;Gopalakrishnan et al, 2015;Vargas et al 2017;Velázquez et al 2017), for example, Rhizobium (Patel et al 1988;Carson et al 1992;Wright et al 2013;Jiménez-Gómez et al 2018), Mesorhizobium (Berraho et al 1997 1987;Lesueur et al 1993;Abd-Alla 1998;Khandelwal et al 2002;Boiero et al 2007), Allorhizobium (Ghosh et al 2015) and Ensifer (Lynch et al 2001).…”

Untitled

“…The nodules were crushed in a small drop of sterile distilled water to obtain milky suspension. Then, serial dilutions were made and aliquots dilutions were spread on yeast extract mannitol agar (YEMA) medium plates were incubated at 28±1°C for 3-5 days 9 .…”

Isolation,Characterization and Optimization of Wild Type Sinorhizobium meliloti to Produce High Concentrations of Indole Acetic Acid

“…Soil bacteria belonging to the Rhizobacteriaceae family, especially Rhizobium bacteria, are of special importance from an agricultural point of view, as they work to increase soil fertility by fixing atmospheric nitrogen [3]. In addition, auxins, especially indole acetic acid, are produced from the amino acid tryptophan by this bacteria during its symbiotic relationship with the legume plant that is specialized in bacterial attraction by roots exudates [4]. Bacterial IAA stimulates the growth of roots and the division of cells infected with the bacteria to form the root nodules.…”