Genome Sequencing and Comparative Transcriptomics of the Model Entomopathogenic Fungi Metarhizium anisopliae and M. acridum

Abstract

Metarhizium spp. are being used as environmentally friendly alternatives to chemical insecticides, as model systems for studying insect-fungus interactions, and as a resource of genes for biotechnology. We present a comparative analysis of the genome sequences of the broad-spectrum insect pathogen Metarhizium anisopliae and the acridid-specific M. acridum. Whole-genome analyses indicate that the genome structures of these two species are highly syntenic and suggest that the genus Metarhizium evolved from plant endophytes or pathogens. Both M. anisopliae and M. acridum have a strikingly larger proportion of genes encoding secreted proteins than other fungi, while ∼30% of these have no functionally characterized homologs, suggesting hitherto unsuspected interactions between fungal pathogens and insects. The analysis of transposase genes provided evidence of repeat-induced point mutations occurring in M. acridum but not in M. anisopliae. With the help of pathogen-host interaction gene database, ∼16% of Metarhizium genes were identified that are similar to experimentally verified genes involved in pathogenicity in other fungi, particularly plant pathogens. However, relative to M. acridum, M. anisopliae has evolved with many expanded gene families of proteases, chitinases, cytochrome P450s, polyketide synthases, and nonribosomal peptide synthetases for cuticle-degradation, detoxification, and toxin biosynthesis that may facilitate its ability to adapt to heterogenous environments. Transcriptional analysis of both fungi during early infection processes provided further insights into the genes and pathways involved in infectivity and specificity. Of particular note, M. acridum transcribed distinct G-protein coupled receptors on cuticles from locusts (the natural hosts) and cockroaches, whereas M. anisopliae transcribed the same receptor on both hosts. This study will facilitate the identification of virulence genes and the development of improved biocontrol strains with customized properties.

Unveiling the biosynthetic puzzle of destruxins in Metarhizium species

“…Dtxs are recognized as important virulence determinants in Metarhizium spp (11)(12)(13). The Metarhizium genus contains a dozen species (14), including M. anisopliae and M. robertsii, which can kill hundreds of insect species, and M. acridum, which can only kill locusts and grasshoppers (15,16). It has frequently been observed that dtx production correlates with host specificity (12,17).…”

Introgression and gene family contraction drive the evolution of lifestyle and host shifts of hypocrealean fungi

“…The RASP yielding ancestral lifestyle and the identification of numerous plant parasitism-related genes in the genomes of Metarhizium spp. also support this hypothesis (Gao et al 2011). …”

“…The utilisation of host-based nutrition is critical for fungal parasitism and includes or carbohydrate-activated enzymes (CAZymes) and as well as proteases, which are among key virulence factors involved in parasitism in various pathogenic fungi (Gao et al 2011; Klosterman et al 2011; Xiao et al 2012). The abundance and types of these enzymes should be key to the adaption to different host-based nutrition.…”

“…Most of the research on genomics in Hypocreales are mainly focused on gene function related to phylogeny, development and pathogenesis, and has revealed the sophisticated strategies associated with the adaption to various lifestyles (Klosterman et al 2011; Rouxel et al 2011). The subtilisins and chitinases, for example, have been shown to be involved in the pathogenesis of insects (Gao et al 2011). Polysaccharide lyases (PLs) and glycoside hydrolases (GHs), enzymes involved in the breakdown of pectin and cellulose in plant cell walls play a role in the infection of plants (Klosterman et al 2011).…”

Specific adaptation of Ustilaginoidea virens in occupying host florets revealed by comparative and functional genomics

“…In contrast, the proteins in the oxidoreduction-driven transporter subclass are expanded (Supplementary Table 18, Supplementary Note 7). Many MFS transporters are involved in the transport of a wide range of nutrient substrates, such as sucrose, galactoside, amino acid and peptides 34 . Reduced MFS transporters and lack of Comparison between the putative PKS gene cluster for ustilaginoidin biosynthesis in U. virens (upper) and the aurofusarin biosynthesis gene cluster in F. graminearum (bottom).…”