Transcriptomic analysis and knockout experiments reveal the role of suhB in the biocontrol effects of Pantoea jilinensis D25 on Botrytis cinerea.

ABSTRACT

Tomato gray mold, caused by Botrytis cinerea, is an important disease in tomato. Pantoea jilinensis D25, isolated form tomato rhizosphere soil, can prevent B. cinerea infection in tomato. To determine the underlying biocontrol mechanism, the transcriptome of P. jilinensis D25 was assessed. Differential expression analysis revealed that 941 genes were upregulated and 997 genes were downregulated. Through transcriptome analysis, the suhB gene was knocked out. ΔPj-suhB exhibited lower swimming motility and colonization abilities than strain D25. After 4 days of co-cultivation, ΔPj-suhB could reduce the colony diameter, mycelial weight, and spore production of B. cinerea with the inhibitory rates of 31.72 %, 39.62 %, and 47.42 %, respectively, compared with control. However, the inhibitory rates of strain D25 were 52.91 %, 60.09 %, and 76.85 %, respectively, compared with control. Strain D25 could significantly downregulate pathogenesis-related genes in B. cinerea, whereas the expression level of these genes in B. cinerea was higher after treatment with ΔPj-suhB than after that with strain D25. In vitro experiments revealed that the lesion area and disease control efficacy were 1.520 and 0.038 cm2 and 68.7 % and 99.0 %, respectively, after ΔPj-suhB and strain D25 treatments. Pot experiments revealed that ΔPj-suhB and strain D25 could prevent tomato plants from B. cinerea infection with the disease reduction rate of 37.5 % and 75.0 %, respectively. Though the activities of defense-related enzymes and expression level of defense related genes in tomato plants were increased under ΔPj-suhB treatment, these effects were higher after strain D25 treatment. Thus, these results demonstrated that suhB was the key gene in strain D25 underlying its biocontrol effect and mobility.