Intrinsic and extrinsic regulatory mechanisms of Pseudomonas palleroniana GZNU148 for enhancing Themeda japonica tolerance to drought stress

Drought is a major abiotic stress that hinders plant growth and crop productivity. However, the intrinsic and extrinsic mechanisms by which Pseudomonas palleroniana GZNU148 increase drought tolerance in Themeda japonica are still unclear.

Physio-biochemical, transcriptomics and 16S rRNA sequencing were employed to examine the effect of GZNU148 on roots’ transcriptional, rhizosphere bacterial community. The rhizosphere soil metabolites analysis was performed by LC-MS. The relationships among rhizosphere bacterial communities, rhizosphere soil differential metabolites and physicochemical properties were explored by co-occurrence networks.

GZNU148 significantly decreased MDA and H₂O₂ content, SOD and CAT activities, and regulated 1158 differentially expressed genes (DEGs) under drought stress. GO terms showed that many DEGs involved in glycogen biosynthetic and sucrose metabolic process. KEGG analysis showed that DEGs were classified into different pathway categories involved in various processes, such as tyrosine metabolism, glycolysis/gluconeogenesis, etc. GZNU148 significantly decreased Chao1 and Shannon index, recruited several beneficial rhizosphere bacterial groups related to carbohydrate metabolism and amino acid metabolism, and increased urease activity in rhizosphere soil under drought stress. GZNU148 also the increased secondary metabolites (SMs) content of rhizosphere soil, which were associated with plant drought, and enhanced the relationships among the rhizosphere soil differential metabolites, physicochemical properties and bacterial communities under drought stress.

GZNU148 improved T. japonica growth under drought stress by increasing the expression levels of drought tolerance related genes (sucrose synthase 4, glucose-6-phosphate isomerase, etc.) in roots, recruiting beneficial rhizosphere bacteria and increasing SMs content in rhizosphere soil.