Sporeless white caps: identification of novel sporulation-related unannotated genes regulating sporogenesis in Agaricomycetes
Csenge Földi1*, Zsolt Merényi1, Balázs Bálint1, Zhihao Hou1, László Galgóczy1,2 and László G. Nagy1
1Synthetic and Systems Biology Unit, Institute of Biochemistry, Biological Research Centre, Szeged, Hungary
2Department of Biotechnology, Faculty of Science and Informatics, University of Szeged, Szeged 6726, Hungary
Spores are the primary means of reproduction in fungi that enable genetic diversity and colonisation of new habitats. At the same time, in industrial settings spores of mushroom-forming fungi (Agaricomycetes) cause respiratory diseases, clog aeration systems, endanger wild populations and enable the spread of viruses in crops; necessitating the development of sporeless mushroom strains. However, the molecular mechanisms of spore production in Agaricomycetes are poorly known. Here we set out to characterise novel, sporogenesis-related, conserved genes in the basidiomycete model organism Coprinopsis cinerea.
First, we performed RNA-Seq analysis spanning the first meiotic division to the appearance of basidiospores, which revealed 1401 genes upregulated at least 3-fold. Of these we chose three, tentatively named sbr1, sbr2 and sbr3, that are highly conserved, contain no known functional domains and based on previously published expression datasets, are exclusively upregulated during sporogenesis. Using the CRISPR/Cas9 system, we disrupted these genes in C. cinerea. Fruiting bodies of the mutants failed to produce spores and accordingly had white caps, in contrast with the wild types, which produced black spores and dark caps. Apart from the lack of spores, mutants displayed wild-type fruiting body morphology. Taken together, these results suggest that sbr1-3 play key roles in sporogenesis in the Agaricomycetes, including commercially produced species like Pleurotus ostreatus making them promising candidates for developing sporeless strains.