Bacterial biosynthesis of 1-aminocyclopropane-1-caboxylate (ACC) deaminase, a useful trait to elongation and endophytic colonization of the roots of rice under constant flooded conditions

Abstract

This study was conducted to investigate the role of 1-aminocyclopropane-1-carboxylate (ACC) deaminase in Pseudomonas fluorescens strain REN 1 and its ability to reduce ethylene levels produced during stress, endophytically colonize and promote the elongation of the roots of rice seedlings under gnotobiotic conditions. We isolated 80 bacteria from inside roots of rice plants grown in the farmers' fields in Guilan, Iran. All of the isolates were characterized for plant growth promoting (PGP) traits. In addition, the colonization assay of these isolates on rice seedlings was carried out to screen for competent endophytes. The best bacterial isolate, based on ACC deaminase production, was identified and used for further study. 16S rDNA sequence analysis revealed that the endophyte was closely related to Pseudomonas fluorescens. The results of this study showed ACC deaminase containing P. fluorescens REN1 increased in vitro root elongation and endophytically colonized the root of rice seedlings significantly, as compared to control under constant flooded conditions. The trait of low amount of indole-3-acetic acid (IAA) production (<15 μg mL −1 ) and the high production of ACC deaminase by bacteria may be main factors in colonizing rice seedling roots compared to other PGP traits (siderophore production and phosphate solubilization) in this study. Endophytic IAA and ACC deaminase-producing bacteria may be preferential selections by rice seedlings. Therefore, it may be suggested that the utilization of ACC as a nutrient gives the isolates advantages in more endophytic colonization and increase of root length of rice seedlings.

Indole-3-acetic acid (IAA) production trait, a useful screening to select endophytic and rhizosphere competent bacteria for rice growth promoting agents

“…For example, whether ACC deaminase producing isolates can also produce IAA or siderophore or solubilize phosphate. In our studies [1] , [7] , it was recognized that all of the reisolated strains from rice seedlings were able to produce IAA. In other words, each isolate having PGP trait had at least the ability of production of IAA too.…”

Plant Growth-Promoting Rhizobacteria: Context, Mechanisms of Action, and Roadmap to Commercialization of Biostimulants for Sustainable Agriculture

“…Beneficial microbes also help plants cope with flooding stress. Rice ( Oryza sativa ) seedlings inoculated with an ACC deaminase producing strain of Pseudomonas fluorescens REN1 increased root elongation under constantly flooded conditions ( Etesami et al, 2014 ).…”

Cannabis Microbiome and the Role of Endophytes in Modulating the Production of Secondary Metabolites: An Overview

“…A mixture of four bacterial endophytes significantly improved CBD and THC contents [91]. Endophyte could manipulate that ACC deaminase level, the precursor of THC biosynthesis in the plant [59,67,122]. Despite these advances, the mechanisms underlying the regulation of THC synthesis have not been completely elucidated.…”