Physiological, biochemical, and global transcriptomic and metabolomic analyses of the effect of the antifungal compound isobavachalcone on Botrytis cinerea on cherry tomatoes

Botrytis cinerea is a major postharvest pathogen on cherry tomato (Solanum lycopersicum). In this study, isobavachalcone (IBC) exhibited inhibitory activity against fungus B. cinerea in vitro and in vivo. Morphological and ultrastructural observations were conducted revealing that IBC caused significant changes in B. cinerea, including rupturing of the cell membrane, loosening of the cell wall, swelling of mitochondria, and massive reductions in the number of ribosomes. Physiological and biochemical analyses confirmed that IBC increased the permeability of the cell wall and membrane which had led to decrease in mitochondrial membrane potential (MMP), while significant increase in reactive oxygen species (ROS) level. According to transcriptomic and metabolomic analysis, IBC inhibited the expression of chitin deacetylase (CDA), glucan 1,3-beta-glucosidase (EXG), and squalene monooxygenase (ERG1) genes, which may result in the degradation of cell wall and membrane components, ultimately increasing cell permeability. IBC also interfered with the expression of cytochrome P450 (CYP102A) and cytochrome-b5 reductase (CYB5R) genes, which had a negative impact on mitochondrial energy metabolism. Additionally, the structure of the ribosomal large subunit and small subunit were altered by IBC, thus, interfering with translation initiation and polypeptide extension. These results provide an effective alternative approach against B. cinerea on cherry tomato.