Bacillus mycoides PM35 Reinforces Photosynthetic Efficiency, Antioxidant Defense, Expression of Stress-Responsive Genes, and Ameliorates the Effects of Salinity Stress in Maize.

Baber Ali,Mehreen Ghazal,Xiukang Wang,Muhammad Siddique Afridi,Shafaqat Ali,Tayyaba Batool,Ayesha Qayyum,Muhammad Hamzah Saleem,Muhammad Atif Azeem,Mehwish Nadeem,Aishah Alatawi

doi:10.3390/life12020219

Abstract

Soil salinity is one of the abiotic constraints that imbalance nutrient acquisition, hampers plant growth, and leads to potential loss in agricultural productivity. Salt-tolerant plant growth-promoting rhizobacteria (PGPR) can alleviate the adverse impacts of salt stress by mediating molecular, biochemical, and physiological status. In the present study, the bacterium Bacillus mycoides PM35 showed resistance up to 3 M NaCl stress and exhibited plant growth-promoting features. Under salinity stress, the halo-tolerant bacterium B. mycoides PM35 showed significant plant growth-promoting traits, such as the production of indole acetic acid, siderophore, ACC deaminase, and exopolysaccharides. Inoculation of B. mycoides PM35 alleviated salt stress in plants and enhanced shoot and root length under salinity stress (0, 300, 600, and 900 mM). The B. mycoides PM35 alleviated salinity stress by enhancing the photosynthetic pigments, carotenoids, radical scavenging capacity, soluble sugars, and protein content in inoculated maize plants compared to non-inoculated plants. In addition, B. mycoides PM35 significantly boosted antioxidant activities, relative water content, flavonoid, phenolic content, and osmolytes while reducing electrolyte leakage, H2O2, and MDA in maize compared to control plants. Genes conferring abiotic stress tolerance (CzcD, sfp, and srfAA genes) were amplified in B. mycoides PM35. Moreover, all reactions are accompanied by the upregulation of stress-related genes (APX and SOD). Our study reveals that B. mycoides PM35 is capable of promoting plant growth and increasing agricultural productivity.

Highlights

Introduction distributed under the terms andSalinity stress negatively affects plant growth and development by unbalancing the nutritional and osmotic potential [1]
Maximum bacterial growth appeared at 1 M concentration of NaCl rather than at 2 and 3 M concentrations
The present study concludes that inoculation of halo-tolerant B. mycoides PM35 containing ACC deaminase and producing EPS significantly alleviates salinity stress in maize plants by producing proline and antioxidant enzymes

Summary

Introduction

Salinity stress negatively affects plant growth and development by unbalancing the nutritional and osmotic potential [1]. Soil salinization is caused by excessive irrigation, conditions of the Creative Commons. Salinity stress is defined as the accumulation of excessive soluble salts in soil, which eventually have detrimental impacts on plant growth and development [5]. Physiology, biochemistry, and molecular processes are affected by salinity stress [6]. Seed germination and plant development are negatively affected by the osmotic and ionic imbalances of Na+ and Cl− [7]. Salinity stress significantly decreases photosynthesis, chlorophyll content, leaf area, stomatal conductance, and the efficiency of photosystem II, which leads to growth hamper and productivity loss [9]. It is crucial to develop and adapt various techniques to use saline land for agricultural productivity [11]

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