Abstract
The Bacillus amyloliquefaciens-SN13 and model crop rice (Oryza sativa) were chosen to understand the complex regulatory networks that govern plant-PGPR interaction under salt stress. During stress, inoculation with SN13 significantly increased biomass, relative water content, proline and total soluble sugar in rice while decreased lipid peroxidation and electrolyte leakage. Extensive alterations in gene expression were also observed in rice root transcriptome under stress in the presence of SN13. Rhizobacteria induced changes in expression of a considerable number of photosynthesis, hormone, and stress-responsive genes, in addition to cell-wall and lipid metabolism-related genes under salt stress as compared to salt stress or SN13 inoculation alone, indicating its potential role in reducing the harmful effects of salinity. To validate RNA-seq data, qRT-PCR was performed for selected differentially expressed genes representing various functional categories including metabolism, regulation, stress-response, and transporters. Results indicate qualitative and quantitative differences between roots responses to SN13 under stressed and unstressed conditions. Functional expressions of OsNAM and OsGRAM in yeast showed enhanced tolerance to various abiotic stresses, indicating crucial SN13-rice interaction in imparting beneficial effects under stress. This is first detailed report on understanding molecular mechanism underlying beneficial plant-microbe interaction in any economically important model crop plant under abiotic stress.
Highlights
Salinity is one of the major stress factor that pose a serious threat to sustainable agricultural production and global food security by causing yield loss of cereal crops[1]
One-week-old rice seedlings were subjected to 7 days of salt stress with and without strain NBRISN13 (SN13) inoculation to determine the effects of SN13-inoculation on root and shoot growth as well as biomass
Based on unique differentially expressed genes (DEGs) found in salt + SN13 sample along with previous literature and established concepts, a functional hypothesis for the mechanism of plant growth promoting rhizobacteria (PGPR)-mediated salt stress tolerance in rice has been elaborated (Fig. 7)
Summary
Salinity is one of the major stress factor that pose a serious threat to sustainable agricultural production and global food security by causing yield loss of cereal crops[1]. Development of varieties for improved salt tolerance through transgenic technology or conventional breeding requires identification of traits or genes that could confer resistance to salinity[1]. Both these approaches are labour and cost intensive as well as time-consuming. Considering the above factors, it has become a prerequisite to use alternate technologies for sustained agricultural production such as the use of plant growth promoting rhizobacteria (PGPR) for salt stress amelioration. Due to its significant phytobeneficial traits and abiotic stress tolerance characteristics, SN13 has emerged as an excellent PGPR for rice which is generally very sensitive to salt stress at young seedling stage but has opened up the area of research pertaining to deciphering the complex molecular networks of perception, response, and adaptation to abiotic stress(s). Present study aimed towards understanding the detailed molecular mechanism underlying beneficial microbe-plant interaction in rice crop exposed to salt stress
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