Bacillus subtilis YN145: effect on melanin synthesis of Magnaporthe oryzae and genome-wide analysis

Abstract:

[Background] Bacillus subtilis YN145 is a bacterial strain isolated from healthy rice plants in Taojiang County of Hunan Province. Studies have demonstrated that YN145 has significant antagonistic effect against Magnaporthe oryzae and great potential in biocontrol. [Objective] To further study the biocontrol mechanism and screen out the gene clusters for secondary metabolite synthesis of this strain. [Methods] The strain YN145, whose extracellular substances had the best inhibitory effect on the melanin synthesis of M. oryzae, was selected from four biocontrol bacterial strains. The absorbance values of the extracellular and intramycelial melanin liquids of M. oryzae were measured by a UV-visible spectrophotometer at a wavelength of 400 nm. The antifungal activity of YN145 was determined by mycelial growth inhibition assay and conidial germination inhibition assay. PacBio Sequel IIe and Illumina Hiseq platforms were employed to sequence the whole genome of YN145, and the sequencing data were assembled and annotated for prediction of gene functions and analysis of the gene clusters for secondary metabolite synthesis. [Results] The extracellular antimicrobial substances of YN1145 effectively inhibited the melanin synthesis, conidial germination, and mycelial growth of M. oryzae. The full-length genome of YN1145 was 4 167 871 bp, with the GC content of 43.86% and coding sequence (CDS) number of 4 294. A total of 85 tRNAs, 30 rRNAs, and 92 sRNAs were identified in the genome. Meanwhile, five known gene clusters for secondary metabolite synthesis were predicted, which mainly encoded bacillaene, bacillibactin, fengycin, subtilosin-A, and baclysin. [Conclusion] This study analyzed the intrinsic reasons for the good antimicrobial effect of YN145 at the genome level and obtained rich basic data. It provides a reference for further in-depth research on the secondary metabolite synthetic pathway of B. subtilis and has great significance for the subsequent research of YN145.