Genomic Basis of Lifestyle Divergence in Rice-Associated Burkholderia: From Pathogenesis to Plant Growth Promotion

The genus Burkholderia encompasses both plant pathogenic and beneficial species, yet the genomic determinants underlying this lifestyle divergence remain poorly understood. Using 16S rRNA sequencing of 100 rice cultivars, our companion study demonstrated that resistant varieties are enriched in beneficial Burkholderiaceae, leading to the isolation of three phenotypically contrasting strains. Here, we present comparative genomic analyses of non-pathogenic biocontrol strain Burkholderia vietnamiensis J14EpLeaf2 and pathogenic strains Burkholderia gladioli A1EpSeed5 and Burkholderia cepacia J14Eple. Pathogenic strains possess significantly larger genomes (8.36-8.46 Mb) enriched in mobile genetic elements compared to the streamlined 6.95 Mb genome of B. vietnamiensis. CAZyme analysis revealed broader repertoires of glycoside hydrolases and polysaccharide lyases in pathogens, consistent with enhanced plant cell wall degradation. B. gladioli possesses a complete T3SS and expanded T6SS with 301 predicted effectors, while B. cepacia lacks structural T3SS genes but harbors 271 candidate effectors predicted to be secreted via alternative secretion pathways, compared to 180 in B. vietnamiensis. Notably, B. cepacia harbors cystic fibrosis-associated markers (cable pili, ZmpA/ZmpB), raising significant biosafety concerns that preclude its agricultural application. LC-MS validated IAA, ornibactin, and AHL production in B. vietnamiensis, supporting its plant growth-promoting and biocontrol functions. Computational PPI networks predicted distinct interaction landscapes requiring experimental validation. This study provides a genomic framework for distinguishing pathogenic from beneficial Burkholderia and supports B. vietnamiensis as a safe biocontrol agent while cautioning against B. cepacia J14Eple.