Abstract
It is commonly accepted that bacteria actively interact with plant host and have beneficial effects on growth and adaptation and grant tolerance to various biotic and abiotic stresses. However, the mechanisms of plant growth promoting bacteria to communicate and adapt to the plant environment are not well characterized. Among the examined bacteria isolates from different saline soils, Arthrobacter nitroguajacolicus was selected as the best plant growth-promoting bacteria under salt stress. To study the effect of bacteria on wheat tolerance to salinity stress, bread wheat seeds were inoculated with A. nitroguajacolicus and grown under salt stress condition. Comparative transcriptome analysis of inoculated and un-inoculated wheat roots under salt stress showed up-regulation of 152 genes whereas 5 genes were significantly down-regulated. Many genes from phenylpropanoid, flavonoid and terpenoid porphyrin and chlorophyll metabolism, stilbenoid, diarylheptanoid metabolism pathways were differentially expressed within inoculated roots under salt stress. Also, a considerable number of genes encoding secondary metabolites such as phenylpropanoids was detected. They are known to take part in lignin biosynthesis of the cell wall as well as antioxidants.
Highlights
Crop yields and biomass is severely reduced by salt stress, primarily causes ionic imbalances leading to harmful effects on nutrient K+ attainment, water uptake, photosynthesis, enzyme activities and metabolism in the presence of high concentrations of Na1
The suspensions of soil were diluted and 100 μl of each suspension was cultured on several medium plates such as yeast extract mannitol agar (YEMA), King’s B (KB) agar, nutrient agar (NA), water yeast extract agar (WYE), glycerol yeast extract agar (GYA), Luria bertani agar (LBA), triptic soy agar (TSA), eosin methylene blue (EMB). the plates were supplemented with 5% NaCl and incubated at 30 ± 2 °C for 3 days
Our results demonstrated that symbiosis of wheat with A. nitroguajacolicus increased shoot and root mass
Summary
Crop yields and biomass is severely reduced by salt stress, primarily causes ionic imbalances leading to harmful effects on nutrient K+ attainment, water uptake, photosynthesis, enzyme activities and metabolism in the presence of high concentrations of Na1. PGPRs induce changes in plants, and growth promotion due to a complex combination of various PGPR-induced mechanisms that affect both plant development as well as plant nutrition such as production of siderophores for iron absorption, plant hormones such as auxins and cytokinins, solubilizing phosphates, minerals and nutrients[7,8,9]. They facilitate plant growth under drought, heavy metals, flood and especially high salinity stresses by reducing the stress through the production of diminase-1-amino-cyclopropane -1-carboxylate (ACC) and altering the selectivity of K+, Na+ and Ca2+ and maintain a higher K+/Na+ ratio[10,11]. Promotion of tolerance to salinity occurs through various mechanisms, including the synthesis of compounds like osmolytes and polyamines, the attenuation of reactive oxygen species (ROSs) by antioxidants, the synthesis of polyamines transporting the ion homeostasis and compartmentalization[12,13,14], nitric oxide formation[15] and the www.nature.com/scientificreports/
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