EST analysis of genes expressed by the zygomycete pathogen Conidiobolus coronatus during growth on insect cuticle

Abstract

Conidiobolus coronatus (Zygomycota) is a facultative saprobe that is a pathogen of many insect species. Almost 2000 expressed sequence tag (EST) cDNA clones were sequenced to analyse gene expression during growth on insect cuticle. Sixty percent of the ESTs that could be clustered into functional groups (E⩽10−5) had their best blast hits among fungal sequences. These included chitinases and multiple subtilisins, trypsin, metalloprotease and aspartyl protease activities with the potential to degrade host tissues and disable anti-microbial peptides. Otherwise, compared to the ascomycete entomopathogen Metarhizium anisopliae, Con. coronatus produced many fewer types of hydrolases (e.g. no phospholipases), antimicrobial agents, toxic secondary metabolites and no ESTs with putative roles in the generation of antibiotics. Instead, Con. coronatus produced a much higher proportion of ESTs encoding ribosomal proteins and enzymes of intermediate metabolism that facilitate its rapid growth. These results are consistent with Con. coronatus having adapted a modification of the saprophytic ruderal-selected strategy, using rapid growth to overwhelm the host and exploit the cadaver before competitors overrun it. This strategy does not preclude specialization to pathogenicity, as Con. coronatus produces the greatest complexity of proteases on insect cuticle, indicating an ability to respond to conditions in the cuticle.

Transcriptome analysis of the entomopathogenic fungus Beauveria bassiana grown on cuticular extracts of the coffee berry borer (Hypothenemus hampei)

“…Expression of such genes involved in general metabolic pathways coupled to antioxidants and host-targeting enzymes appeared similar among B. bassiana and C. coronatus. Among the genes expressed in C. coronatus are the antioxidants c-glutamylcysteine synthetase and gluthatione reductase, subtilisin type hydrolases including metalloprotease, trypsin protease and aspartyl protease and antimicrobials similar to cytochrome p450 of tobacco and cephalosporin (Freimoser et al, 2003b). As indicated from our EST analysis some similar metabolic pathways are also present in B. bassiana.…”

The cuticular fatty acids of Calliphora vicina, Dendrolimus pini and Galleria mellonella larvae and their role in resistance to fungal infection

“…endoproteases, aminopetidases, carboxypetidases, N-acetylglucosoaminidases, chitinases, esterases, and lipases which determine fungal virulence (Gillespie et al, 2000). The relatively little investigated entomopathogen C. coronatus secretes a great complexity of proteinases into culture media (Sutar et al, 1991;Phadatare et al, 1992;Freimoser et al, 2003;Bania et al, 2006). The EST (expressed sequence tags) strategy, a rapid and relatively efficient method for the speedy discovery of large numbers of genes in organisms which have little or no genetic research, has confirmed our report that C. coronatus produces a chitinolytic complex to degrade cuticular components (Czygier et al, 2000;Freimoser et al, 2003).…”

Secretome of fungus-infected aphids documents high pathogen activity and weak host response

“…Leger et al, 1996a;Zhang et al, 2008). A number of clones deduced to encode cuticle-degrading enzymes were identified in two EST studies with cultures of the entomophthoralean pathogens Conidiobolus coronatus and Zoophthora radicans, grown on insect cuticle and isolated from lepidopteran larvae, respectively (Freimoser et al, 2003;Xu et al, 2009). Our findings were substantiated by the identification of homologous clones in these libraries (Table 2, EST hits).…”