Abstract
The objectives of this study were to evaluate the plant growth promoting effects on Arabidopsis by Pseudomonas sp. strains associated with rhizosphere of crop plants grown in Mekong Delta, Vietnam. Out of all the screened isolates, Pseudomonas PS01 isolated from maize rhizosphere showed the most prominent plant growth promoting effects on Arabidopsis and maize (Zea mays). We also found that PS01 altered root system architecture (RSA). The full genome of PS01 was resolved using high-throughput sequencing. Phylogenetic analysis identified PS01 as a member of the Pseudomonas putida subclade, which is closely related to Pseudomonas taiwanensis. PS01 genome size is 5.3 Mb, assembled in 71 scaffolds comprising of 4820 putative coding sequence. PS01 encodes genes for the indole-3-acetic acid (IAA), acetoin and 2,3-butanediol biosynthesis pathways. PS01 promoted the growth of Arabidopsis and altered the root system architecture by inhibiting primary root elongation and promoting lateral root and root hair formation. By employing gene expression analysis, genetic screening and pharmacological approaches, we suggested that the plant-growth promoting effects of PS01 and the alteration of RSA might be independent of bacterial auxin and could be caused by a combination of different diffusible compounds and volatile organic compounds (VOCs). Taken together, our results suggest that PS01 is a potential candidate to be used as bio-fertilizer agent for enhancing plant growth.
Highlights
Plant growth-promoting rhizobacteria (PGPR) colonize the rhizosphere and play a key role in the improvement of plant fitness and yield [1]
Thereby, the present study aims to (i) screen and select a novel strain of Pseudomonas spp. which was isolated from rhizospheres of some plant species grown on the Mekong Delta, (ii) characterize the effects of the isolate with respect to plant growth promotion and alteration of root system architecture (RSA), and (iii) investigate the relevant molecular mechanisms
Our results suggested that Pseudomonas PS01-induced modulation of the RSA and plant growth probably involves distinct signaling pathways, and that Pseudomonas PS01 could be commercialized as a bio-inoculant, which could be applied for a sustainable agriculture development
Summary
Plant growth-promoting rhizobacteria (PGPR) colonize the rhizosphere and play a key role in the improvement of plant fitness and yield [1]. The genus Pseudomonas is one of the most abundant genera of PGPR, which is capable of enhancing plant growth and modulating the root system architecture in different plant species [2,3,4]. Pseudomonas spp. promote plant growth or modulate root development by producing and secreting phytohormones (e.g., indole-3-acetic acid, IAA) and/or volatile organic compounds (VOCs) [4,12,13,14,15,16,17]. Some Pseudomonas species produce IAA, which can enhance plant growth and alter root system architecture. Some bacterial VOCs such as 2,3-butanediol, 3-hydroxy-2butanone, 2-pentylfuran, N,N-dimethyl-hexadecanamine, carbon dioxide (CO2), 13-tetradecadien-1-ol, 2-butanone and 2-methyl-n-1- tridecene promote plant growth and modulate root system architecture. P. fluorescens SS101 promotes the growth of plants via the release of VOCs including 13-Tetradecadien1-ol, 2-butanone and 2-Methyl-n-1-tridecene [17]
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