Microbial Volatile Organic Compounds (mVOCs) from rhizobacterium RL-WG62 mediate salt tolerance in Brassica napus by reprogramming transcriptome

Salt stress severely constrains Brassica napus production, and utilizing beneficial microorganisms to enhance crop salt tolerance represents a sustainable strategy. Microbial volatile organic compounds (mVOCs), as crucial signaling molecules, play an important role in plant-microbe interactions. This study investigated plant growth-promoting rhizobacteria (PGPR) Rossellomorea vietnamensis RL-WG62, isolated from the rhizosphere of seawater rice 86 (SR86), to assess its ability to enhance salt tolerance in rapeseed. Field and laboratory experiments showed that RL-WG62 significantly improved rapeseed seedling survival and germination rate under salt stress, respectively. Further, using a split-plate co-culture system to prevent direct contact between strain RL-WG62 and rapeseed, strain RL-WG62 was shown to enhance the growth of salt-stressed B. napus by increasing root length, lateral root number, and biomass, while reducing malondialdehyde (MDA) content and elevating superoxide dismutase (SOD) activity. These results indicated that the promotion of growth and salt tolerance is mediated by mVOCs released from RL-WG62. Among these mVOCs, methyl thioacetate, 1-bromooctane, and dimethyl trisulfide proved effective in promoting rapeseed growth. what’s more, transcriptomic analysis revealed that 287 genes were specifically induced by RL-WG62 in B. napus under salt stress. Functional analysis and qRT-PCR validation demonstrated that RL-WG62, through the release of mVOCs, could activate plant hormone signaling (ABA, JA, and IAA), the MAPK signaling pathway, root development, and abiotic stress responses, thereby establishing a defense system against salt stress in rapeseed. This study provided valuable information, indicating that strain RL-WG62 could enhance salt stress tolerance in B. napus by releasing mVOCs and clarifying the underlying mechanism.