title: Secondary metabolite gene clusters in the entomopathogen fungus Metarhizium anisopliae: genome identification and patterns of expression in a cuticle infection model.
abstract: The described species from the Metarhizium genus are cosmopolitan fungi that infect arthropod hosts. Interestingly, while some species infect a wide range of hosts (host-generalists), other species infect only a few arthropods (host-specialists). This singular evolutionary trait permits unique comparisons to determine how pathogens and virulence determinants emerge. Among the several virulence determinants that have been described, secondary metabolites (SMs) are suggested to play essential roles during fungal infection. Despite progress in the study of pathogen-host relationships, the majority of genes related to SM production in Metarhizium spp. are uncharacterized, and little is known about their genomic organization, expression and regulation. To better understand how infection conditions may affect SM production in Metarhizium anisopliae, we have performed a deep survey and description of SM biosynthetic gene clusters (BGCs) in M. anisopliae, analyzed RNA-seq data from fungi grown on cattle-tick cuticles, evaluated the differential expression of BGCs, and assessed conservation among the Metarhizium genus. Furthermore, our analysis extended to the construction of a phylogeny for the following three BGCs: a tropolone/citrinin-related compound (MaPKS1), a pseurotin-related compound (MaNRPS-PKS2), and a putative helvolic acid (MaTERP1).
  
  
  
  Among 73 BGCs identified in M. anisopliae, 20 % were up-regulated during initial tick cuticle infection and presumably possess virulence-related roles. These up-regulated BGCs include known clusters, such as destruxin, NG39x and ferricrocin, together with putative helvolic acid and, pseurotin and tropolone/citrinin-related compound clusters as well as uncharacterized clusters. Furthermore, several previously characterized and putative BGCs were silent or down-regulated in initial infection conditions, indicating minor participation over the course of infection. Interestingly, several up-regulated BGCs were not conserved in host-specialist species from the Metarhizium genus, indicating differences in the metabolic strategies employed by generalist and specialist species to overcome and kill their host. These differences in metabolic potential may have been partially shaped by horizontal gene transfer (HGT) events, as our phylogenetic analysis provided evidence that the putative helvolic acid cluster in Metarhizium spp. originated from an HGT event.
  
  
  
  Several unknown BGCs are described, and aspects of their organization, regulation and origin are discussed, providing further support for the impact of SM on the Metarhizium genus lifestyle and infection process.
authors: Rede Avançada em Biologia Computacional, RABICÓ, Petrópolis, RJ, Brazil.|Centro de Biotecnologia, Programa de Pós-graduação em Biologia Celular e Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors: Nicolau
authors: N
authors: Sbaraini
authors: Rede Avançada em Biologia Computacional, RABICÓ, Petrópolis, RJ, Brazil.|Laboratório Nacional de Computação Científica, LNCC, Petrópolis, RJ, Brazil.
authors: Rafael Lucas Muniz
authors: RL
authors: Guedes
authors: Rede Avançada em Biologia Computacional, RABICÓ, Petrópolis, RJ, Brazil.|Centro de Biotecnologia, Programa de Pós-graduação em Biologia Celular e Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors: Fábio Carrer
authors: FC
authors: Andreis
authors: Rede Avançada em Biologia Computacional, RABICÓ, Petrópolis, RJ, Brazil.|Centro de Biotecnologia, Programa de Pós-graduação em Biologia Celular e Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors: Ângela
authors: Â
authors: Junges
authors: Rede Avançada em Biologia Computacional, RABICÓ, Petrópolis, RJ, Brazil.|Centro de Biotecnologia, Programa de Pós-graduação em Biologia Celular e Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.|Laboratório Nacional de Computação Científica, LNCC, Petrópolis, RJ, Brazil.
authors: Guilherme Loss
authors: GL
authors: de Morais
authors: Rede Avançada em Biologia Computacional, RABICÓ, Petrópolis, RJ, Brazil.|Centro de Biotecnologia, Programa de Pós-graduação em Biologia Celular e Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
authors: Marilene Henning
authors: MH
authors: Vainstein
authors: Rede Avançada em Biologia Computacional, RABICÓ, Petrópolis, RJ, Brazil.|Laboratório Nacional de Computação Científica, LNCC, Petrópolis, RJ, Brazil.
authors: Ana Tereza Ribeiro
authors: AT
authors: de Vasconcelos
authors: Rede Avançada em Biologia Computacional, RABICÓ, Petrópolis, RJ, Brazil. aschrank@cbiot.ufrgs.br.|Centro de Biotecnologia, Programa de Pós-graduação em Biologia Celular e Molecular, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil. aschrank@cbiot.ufrgs.br.
authors: Augusto
authors: A
authors: Schrank
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D023061:Gene Order; D016681:Genome, Fungal; D023281:Genomics / Q000379:methods; D054884:Host-Pathogen Interactions; D052981:Metarhizium / Q000145:classification / Q000235:genetics* / Q000378:metabolism*; D010802:Phylogeny; D019655:Quantitative Trait, Heritable; D064210:Secondary Metabolism / Q000235:genetics*; D013987:Ticks / Q000382:microbiology; D059467:Transcriptome
keywords: Biological control; Cattle tick; Infection process; Metarhizium spp; Secondary metabolite biosynthetic gene clusters; Transcriptome analysis