Transcriptomic and metabolomic analysis of the mechanism by which Bacillus tequilensis inhibits Alternaria alternata to control pear black spot

Pear black spot caused by Alternaria alternata is widespread in Chinese orchards, causing serious losses. Screening of effective biocontrol microorganisms is important for controlling this disease. Bacillus tequilensis 2_2a has biocontrol potential. This study aimed to verify the antifungal activity of B. tequilensis against A. alternata and biocontrol effect on pear black spot, to elucidate by transcriptomic and metabolomic approach, the molecular pathway underlying to effect of strain against A. alternata, to validate the effect on genes and metabolic components related to the molecular action mechanisms, and to analyse the mechanisms and molecular targets of the biocontroller bacteria. The results showed that B. tequilensis inhibited mycelial growth. B. tequilensis caused A. alternata mycelial aggregation, twisting, and entanglement. B. tequilensis controlled pear black spot by over 90%. Six pathways were related to the key differentially expressed genes and metabolites of B. tequilensis-treated A. alternata: glycolysis, citric acid cycle, oxidative phosphorylation, pentose phosphate pathway, pyrimidine metabolism and cell cycle. Validated changes in the expression of key genes were consistent with the transcriptomic data, and the interactions among these pathways mainly affected glucose conversion, citric acid synthesis, intracellular redox-related biosynthesis of pyridine nucleotides, and adenine nucleotides that provide energy. This research helps to promote the biocontrol agent B. tequilensis, as it provides the mechanism behind its biocontrol efficacy.