Bacillus safensis from wheat rhizosphere promotes growth and ameliorates salinity stress in wheat

Bacillus safensis (W10) from wheat rhizosphere which could grow in medium with high concentration of sodium chloride selected for this study showed positive response in in vitro plant growth promoting rhizobacteria (PGPR) tests such as phosphate solubilization, siderophore production, indole acetic acid (IAA) production and 1 aminocyclopropane-1-carboxylase (ACC) deaminase activity. The growth of six cultivars of wheat under normal as well as salt-stressed conditions was promoted by this bacterium also enhanced the tolerance of wheat cultivars to salinity. Activities of antioxidant enzymes were enhanced due to salinity, but not by bacterial application, while those of defense enzymes were significantly enhanced due to application of W10 alone or with NaCl treatment. Microarray and bioinformatic analysis for comparing gene expression in seedlings under salinity stress against those under salinity stress along with bacterial application revealed an up-regulation of 3731 genes and down-regulation of 6312 genes. Some of the up-regulated genes included those for expansins, endotransglucoslylase/hydrolase, sulphur-rich thionin, S-adenosylmethionine decarboxylase precursor and metallothionines while down regulated ones included those for flavanone hydroxylase, oxalate oxidase, protein phosphatase etc. Probably, salinity stress in wheat is alleviated mainly not through enhanced antioxidant systems but up-regulation of several other genes involved in tolerance to salinity as well as defense against biotic stress.