Engineered production of 2,4-diacetylphloroglucinol in the diazotrophic endophytic bacterium Pseudomonas sp WS5 and its beneficial effect in multiple plant-pathogen systems

The 2,4-diacetylphloroglucinol (2,4-DAPG) biosynthetic gene clusters were amplified from Pseudomonas protegee Pf-5 and Pseudomonas sp. G22 (lab isolate) and cloned into pUCPM18Gm vector for constitutive expression in diazotrophic endophytic Pseudomonas sp. WS5 isolated from wheat plant 2,4-DAPG production in recombinant strains as quantitated by HPLC analysis was 12-14 mu g ml(-1) while the native 2,4-DAPG producing strains showed < 2 mu g ml(-1). The antifungal extract of the recombinant strains showed antagonistic effect against Magnaporthe oryzae B157 and Rhizoctonia solani. Endophytic colonization and plant protection ability of recombinant strains was observed in rice, sorghum, and wheat after 60 d of growth in plants challenged with the fungal pathogens, indicating the endophytic recombinant strain was effective in promoting the plant growth during infection. Pathogenesis-related genes expression in rice plants as analyzed by qPCR showed that the rice plants colonized by 2,4-DAPG producing recombinant strain when challenged with M. oryzae B157 had elevated levels of NPR1 and PR10a gene expression.