Pseudomonas koreensis promotes tomato growth and shows potential to induce stress tolerance via auxin and polyphenol‐related pathways

Pseudomonas koreensis, a subgroup of the P. fluorescens complex, is a potential plant growth-promoting rhizobacterium. This study explored the mechanisms of plant growth promotion by P. koreensis and its potential to induce stress tolerance in tomato. Tomato plants in pots were inoculated with P. koreensis GS and cultured for 60 days. RNA sequencing and gas chromatography-mass spectrometry were used to detect global transcriptomic and metabolomic changes in tomato leaves. Liquid chromatography-mass spectrometry was used for quantification of plant hormones. The inoculated plants showed more vigorous growth, with higher leaf chlorophyll content and shoot biomass compared with uninoculated controls. The activities of several defense enzymes (e.g., phenylalanine ammonia-lyase) were enhanced in the leaves of inoculated plants. A total of 737 differentially expressed genes were identified, which were related to plant hormone biosynthesis, MAPK signaling transduction, and polyphenol biosynthesis. The contents of specific metabolites related to plant growth and stress tolerance, including polyphenols (phenylpropanoids) and amino acids (tryptophanand and proline), were increased after inoculation. Plant hormones such as indole-3-acetic acid participated in plant growth promotion by P. koreensis. P. koreensis promoted plant growth and showed potential to induce stress tolerance in tomato by enhancing auxin and polyphenol-related pathways.