Abstract
BackgroundEntomopathogenic fungi such as Beauveria bassiana are promising biological agents for control of malaria mosquitoes. Indeed, infection with B. bassiana reduces the lifespan of mosquitoes in the laboratory and in the field. Natural isolates of B. bassiana show up to 10-fold differences in virulence between the most and the least virulent isolate. In this study, we sequenced the genomes of five isolates representing the extremes of low/high virulence and three RNA libraries, and applied a genome comparison approach to uncover genetic mechanisms underpinning virulence.ResultsA high-quality, near-complete genome assembly was achieved for the highly virulent isolate Bb8028, which was compared to the assemblies of the four other isolates. Whole genome analysis showed a high level of genetic diversity between the five isolates (2.85–16.8 SNPs/kb), which grouped into two distinct phylogenetic clusters. Mating type gene analysis revealed the presence of either the MAT1–1–1 or the MAT1–2–1 gene. Moreover, a putative new MAT gene (MAT1-2–8) was detected in the MAT1–2 locus. Comparative genome analysis revealed that Bb8028 contains 163 genes exclusive for this isolate. These unique genes have a tendency to cluster in the genome and to be often located near the telomeres. Among the genes unique to Bb8028 are a Non-Ribosomal Peptide Synthetase (NRPS) secondary metabolite gene cluster, a polyketide synthase (PKS) gene, and five genes with homology to bacterial toxins. A survey of candidate virulence genes for B. bassiana is presented.ConclusionsOur results indicate several genes and molecular processes that may underpin virulence towards mosquitoes. Thus, the genome sequences of five isolates of B. bassiana provide a better understanding of the natural variation in virulence and will offer a major resource for future research on this important biological control agent.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3339-1) contains supplementary material, which is available to authorized users.
Highlights
Entomopathogenic fungi such as Beauveria bassiana are promising biological agents for control of malaria mosquitoes
A high-quality Beauveria bassiana reference genome Five B. bassiana isolates were sequenced that were previously phenotyped for virulence against malaria mosquitoes
This isolate was sequenced with both short and long-reads, single molecule sequencing technology, while two isolates were sequenced with short reads on both short and long insert libraries (Bb1520 and Bb2597), and two isolates were sequenced with short reads only on short insert libraries (Bb4305 and Bb5078)
Summary
Entomopathogenic fungi such as Beauveria bassiana are promising biological agents for control of malaria mosquitoes. Infection by B. bassiana starts when conidia adhere to the host cuticle via hydrophobic interactions and subsequently germinate. Once the host is dead, the fungus breaches the cuticle from the inside outwards, allowing the formation of conidia that upon dispersal start new infections [10]. A good understanding of the life history of B. bassiana as well as the genetic mechanisms of virulence is crucial to develop it as an effective and sustainable biological control agent. Substantial progress has been made in the genetic characterization of the mechanisms involved in the infection cycle of B. bassiana inside insects. Many of the recent findings regarding genes involved in virulence were possible due to the development of reliable protocols that allow genetic manipulation [11] together with the availability of a draft genome sequence [12]. A ΔBbcyp52x1 knock-out mutant showed reduced virulence on Galleria mellonella upon topical application of conidia, though not upon intra-hemocoel injection [14]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
