Functional Genomic Analysis of Bacillus thuringiensisC25 Reveals the Potential Genes Regulating Antifungal Activity against Rosellinia necatrix

Kangmin Kim¹² Hwa-Yong Lee ³ Wonsil Bae³ Min Cho^1,2,* Hojin Ryu^3,*

¹Division of Biotechnology, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 54596, Korea
²Safety, Environment, and Life Sciences Center, Chonbuk National University, Iksan 54596, Korea
³Department of Biology, Chungbuk National University, Cheongju 28644, Korea

Abstract

biocontrol agents (BCAs) are widely used to protect plants from diverse biotic and abiotic stresses in agricultural and ecological fields. Among the various microbes, many subspecies of the gram-positive genus, Bacillus, have been successfully industrialized as eco-friendly biological pesticides and fertilizers. In the current study, we demonstrated that Bacillus thuringiensis C25 exhibited antagonistic effects on the mycelial growth of Rosellinia necatrix, a fungal phytopathogen. Scanning electron microscopy analysis revealed that B. thuringiensis C25 degraded the cell wall structures of R. necatrix mycelia. In the functional genomic analysis of B. thuringiensis C25, we annotated 5,683 genes and selected the gene sets that potentially encoded fungal cell wall degrading enzymes (CWDEs). The growth inhibition effects on R. necatrix were highly correlated with the transcriptional activity of the mycelial cell wall degrading genes of B. thuringiensis C25. The transcript levels of CWDEs, including CshiA, B, and Glycos_transf_2 genes in B. thuringiensis C25, were enhanced following co-cultivation with R. necatrix. In conclusion, our study suggested that B. thuringiensis C25 could serve as a suitable candidate for controlling R. necatrix and could facilitate elucidating the mechanisms underlying the antifungal activities of BCAs against phytopathogens.

Figures & Tables

Fig. 1. Antifungal effects of B. C25 against R. . A, The inhibition of mycelial growth of R. in presence of B. C25. Two agar plugs (9 mm in diameter per each) of R. (KACC 40168 and KACC 40445) were put on the opposite sides of PDA plate. Then, B. C25 suspension was in℃ulated on the central line on PDA plates and subjected to incubation for 5 days at 28±1°C. B, The growth inhibition rates of mycelia of R. KACC 40168/40445 in presence of B. C25. The radius of mycelia of R. in the absence and presence of B. C25 were relatively compared and presented as percentage.