A Salt-Tolerant Streptomyces paradoxus D2-8 from Rhizosphere Soil of Phragmites communis Augments Soybean Tolerance to Soda Saline-Alkali Stress

Abstract

Soil salinity and alkalization limit plant growth and agricultural productivity worldwide. The application of salt-tolerant plant growth-promoting rhizobacteria (PGPR) effectively improved plant tolerance to saline-alkali stress. To obtain the beneficial actinomyces resources with salt tolerance, thirteen isolates were isolated from rhizosphere saline and alkaline soil of Phragmites communis. Among these isolates, D2-8 was moderately halophilic to NaCl and showed 120 mmol soda saline-alkali solution tolerance. Moreover, the plant growth-promoting test demonstrated that D2-8 produced siderophore, IAA, 1-aminocyclopropane-1-carboxylate deaminase (ACCD), and organic acids. D2-8 showed 99.4% homology with the type strain Streptomyces paradoxus NBRC 14887T and shared the same branch, and, therefore, it was designated S. paradoxus D2-8. Its genome was sequenced to gain insight into the mechanism of growth-promoting and saline-alkali tolerance of D2-8. IAA and siderophore biosynthesis pathway, genes encoding ACC deaminase, together with six antibiotics biosynthesis gene clusters with antifungal or antibacterial activity, were identified. The compatible solute ectoine biosynthesis gene cluster, production, and uptake of choline and glycine betaine cluster in the D2-8 genome may contribute to the saline-alkali tolerance of the strain. Furthermore, D2-8 significantly promoted the seedling growth even under soda saline-alkali stress, and seed coating with D2-8 isolate increased by 5.88% of the soybean yield in the field. These results imply its significant potential to improve soybean soda saline-alkali tolerance and promote crop health in alkaline soil.

Metagenomic assembled genomes indicated the potential application of hypersaline microbiome for plant growth promotion and stress alleviation in salinized soils

“…IAAs serve as an auxin regulating plant growth and development. Several examples of the rhizosphere halophiles exhibiting siderophore production, potassium solubilization, and IAA synthesis were also observed ( 53 , 54 ). The production of EPS is also a crucial PGP attribute because it facilitates the initial root colonization by microbes and the production of a water-rich polysaccharide layer around roots, which acts as a barrier preventing them from excess ionic salts.…”

Inoculation with Actinobacteria spp. Isolated from a Hyper-Arid Environment Enhances Tolerance to Salinity in Lettuce Plants (Lactuca sativa L.)

“…In this work, we insolated four actinobacterial strains from the Atacama Desert and based on 16S gene sequencing one insolated had 98.99% of similarity with the genus Pseudarthrobacter and the rest of them had 99.08–99.79% with the genus Streptomyces. Both genera isolated here have been reported, such as plant-promoting rhizobacteria with the ability of fixing nitrogen, solubilizing phosphate, producing siderophores and auxin, and was use for improving salt tolerance in tomato [ 25 , 26 ], sage [ 27 ], maize [ 28 ], wheat [ 29 ], and soybean [ 30 ].…”

Actinobacteria–Plant Interactions in Alleviating Abiotic Stress

“…Genes related to PGP-traits including IAA biosynthesis, ACC deaminase, and ammonia assimilation were found in the genome of S. paradoxus D2-8. Genes related to stress tolerance including osmolytes such as ectoine and genes involved in the production and uptake of choline and glycine betaine were also detected [ 116 ]. A detailed list of genes that help in alleviating abiotic stress in plants is in Table 1 .…”