Multi-omics integration reveals glucosinolate biosynthesis as a regulatory hub coordinating combined heat and salt stress responses in cabbage (Brassica oleracea L.)

Abstract

Global warming has intensified the concurrent occurrence of heat and salt stress, posing a significant threat to cabbage production. However, the regulatory mechanisms governing cabbage responses to this stress combination remain largely elusive. Here, we integrated physiological, transcriptomic, and metabolomic analyses to decipher the stress response strategies of four cabbage genotypes with contrasting heat or salt tolerance. While combined stress suppressed growth and photosynthetic parameters across different genotypes, physiological profiling revealed that salt stress is the primary driver of injury under combined conditions. Based on the levels of H₂O₂ and the Fv/Fm ratio in leaves, analyses showed that 48 h of stress represented a critical juncture marked by maximal photoinhibition and reactive oxygen species accumulation. Transcriptomic and metabolomic analyses showed that 5255 differentially expressed genes (DEGs) and 857 differentially abundant metabolites (DAMs) were identified in the salt-tolerant genotype ‘JSA9’, while 9019 DEGs and 858 DAMs were identified in the heat-tolerant genotype ‘JSA12’ under combined stress. Crucially, integrated multi-omics network analysis unveiled the glucosinolate biosynthesis pathway as a central regulatory hub coordinating the combined stress response, a role that has not been previously characterized in cabbage under combined heat and salt stress. This pathway exhibited genotype-specific regulatory architectures, with key genes including CYP79B2-1, BCAT4, and ST5a-2 displaying divergent expression patterns linked to distinct adaptive strategies. Collectively, our findings establish a high-resolution molecular framework for combined stress adaptation in cabbage and identify a set of candidate genes for functional validation and breeding of multi-stress-tolerant varieties.