Functional analysis of developmentally regulated genes \(\it chs7\) and \(\it sec22\) in the Ascomycete \(\textit {Sordaria macrospora}\)

During sexual development, filamentous ascomycetes form complex, three-dimensional fruiting bodies for the generation and dispersal of spores. In previous studies, we identified genes with evolutionary conserved expression patterns during fruiting body formation in several fungal species. Here, we present the functional analysis of two developmentally up-regulated genes, \(\it chs7\) and \(\it sec22\), in the ascomycete \(\textit {Sordaria macrospora}\). The genes encode a class VII (division III) chitin synthase and a soluble \(\it N\)-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) protein, respectively. Deletion mutants of \(\it chs7\) had normal vegetative growth and were fully fertile but showed sensitivity toward cell wall stress. Deletion of \(\it sec22\) resulted in a reduced number of ascospores and in defects in ascospore pigmentation and germination, whereas vegetative growth was normal in the mutant. A SEC22-EGFP fusion construct under control of the native \(\it sec22\) promoter and terminator regions was expressed during different stages of sexual development. Expression of several development-related genes was deregulated in the \(\it sec22\) mutant, including three genes involved in melanin biosynthesis. Our data indicate that \(\it chs7\) is dispensable for fruiting body formation in \(\textit {S. macrospora}\), whereas \(\it sec22\) is required for ascospore maturation and germination and thus involved in late stages of sexual development