Comparative transcriptomics of the model mushroom Coprinopsis cinerea reveals tissue-specific armories and a conserved circuitry for sexual development

Abstract

BackgroundIt is well known that mushrooms produce defense proteins and secondary metabolites against predators and competitors; however, less is known about the correlation between the tissue-specific expression and the target organism (antagonist) specificity of these molecules. In addition, conserved transcriptional circuitries involved in developing sexual organs in fungi are not characterized, despite the growing number of gene expression datasets available from reproductive and vegetative tissue. The aims of this study were: first, to evaluate the tissue specificity of defense gene expression in the model mushroom Coprinopsis cinerea and, second, to assess the degree of conservation in transcriptional regulation during sexual development in basidiomycetes.ResultsIn order to characterize the regulation in the expression of defense loci and the transcriptional circuitries controlling sexual reproduction in basidiomycetes, we sequenced the poly (A)-positive transcriptome of stage 1 primordia and vegetative mycelium of C. cinerea A43mutB43mut. Our data show that many genes encoding predicted and already characterized defense proteins are differentially expressed in these tissues. The predicted specificity of these proteins with regard to target organisms suggests that their expression pattern correlates with the type of antagonists these tissues are confronted with. Accordingly, we show that the stage 1 primordium-specific protein CC1G_11805 is toxic to insects and nematodes. Comparison of our data to analogous data from Laccaria bicolor and Schizophyllum commune revealed that the transcriptional regulation of nearly 70 loci is conserved and probably subjected to stabilizing selection. A Velvet domain-containing protein was found to be up-regulated in all three fungi, providing preliminary evidence of a possible role of the Velvet protein family in sexual development of basidiomycetes. The PBS-soluble proteome of C. cinerea primordia and mycelium was analyzed by shotgun LC-MS. This proteome data confirmed the presence of intracellular defense proteins in primordia.ConclusionsThis study shows that the exposure of different tissues in fungi to different types of antagonists shapes the expression pattern of defense loci in a tissue-specific manner. Furthermore, we identify a transcriptional circuitry conserved among basidiomycetes during fruiting body formation that involves, amongst other transcription factors, the up-regulation of a Velvet domain-containing protein.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-492) contains supplementary material, which is available to authorized users.

Entomotoxic and nematotoxic lectins and protease inhibitors from fungal fruiting bodies

“…MOA and the C. cinerea homolog of LSL have nematotoxic and the latter also entomotoxic activity (Plaza et al 2014;Wohlschlager et al 2011). LSL was shown to associate into hexamers in solution and crystals (Mancheno et al 2005).…”

“…SCA exhibits the carbohydrate-binding specificity of MOA but not its catalytic activity ). On the other hand, the homology of LSL to fruiting bodyspecific proteins of C. cinerea is restricted to the aerolysin domain (Plaza et al 2014). SCA and the C. cinerea homolog of LSL are differentially expressed in fruiting bodies compared to the vegetative mycelium in S. commune and in C. cinerea (Ohm et al 2010;Plaza et al 2014).…”

“…Galectins CGL1 and CGL2 are highly abundant in young fruiting bodies but hardly produced in the vegetative mycelium of C. cinerea (Boulianne et al 2000;Plaza et al 2014). Expression of the genes is, however, induced in the vegetative mycelium upon challenge of this tissue with the fungivorous nematode Aphelenchus avenae .…”

“…Based on the accumulation of protein during sclerotium formation and its depletion during mycelium germination, a storage function for RSA in R. solani has been proposed. CCL2 and its paralog CCL1 exhibit a pronounced fruiting body-specific expression with almost no expression in the vegetative mycelium of C. cinerea (Plaza et al 2014;Schubert et al 2012).…”

“…The numbers and specificities of the carbohydrate-binding sites of the β-trefoil domains differ in that all three canonical binding sites of MOA are functional and bind to glycans carrying terminal Gal-α1,3-Gal/ GalNAc-β epitopes (Grahn et al 2007;Grahn et al 2009;Wohlschlager et al 2011) while only two of the three canonical binding sites of LSL appear to be functional and specific for β-galactosides including lactose and LacNAc (Angulo et al 2011;Mancheno et al 2005). Homologs of both proteins from other dikaryotic fungi have been partially characterized (Chumkhunthod et al 2006;Kadirvelraj et al 2011;Plaza et al 2014;Wohlschlager et al 2011). The MOA homologs PSL and SCA (Schizophyllum commune agglutinin), from the saprophytic mushrooms Polyporus squamosus and S. commune, differ from MOA in that PSL harbors a lower number of functional carbohydrate-binding sites with a different specificity toward terminal Neu5Ac-α2,6-Gal-β epitopes but with the catalytic triad of the cysteine protease domain conserved (Kadirvelraj et al 2011;Wohlschlager et al 2011).…”