Research progress on the drought resistance mechanism of plant growth promoting bacteria and plant interactions

Drought is one of the major causes of global vegetation degradation and agricultural yields loss. Beneficial microorganisms, as “second genome”, help the plants cope with environmental stress. Plant growth promoting bacteria (PGPB) are important beneficial microorganisms, and classified into rhizospheric, phyllospheric, and endophytic groups based on their colonization. Under drought stress, PGPB help plants manage osmotic stress by secreting plant hormones or modulating the host's hormonal metabolism, alleviate oxidative damage by enhancing antioxidant enzyme activity and gene expression, and improve water and nutrient uptake by promoting stomatal conductance and root development. This review, based on our researchs for PGPBs derived from desert plants, outlines the main bacterial groups and their mechanisms in drought resistance, including osmotic and hormonal regulation, antioxidant defense, and nutrient absorption. We also introduce relevant strains and plant genes, and would provide references for crop cultivation and molecular breeding under drought.