this case, the cas2 open reading frame starts with a CTG, encoding for Leu37 in the original gene, instead of the ATG start codon. Found DOC) Construction of double knock-out strains Conventional genetic analyses were used to generate double knock-out strains as described previously [23]. Two single knock- out strains were crossed on BMM medium plates and asci from recombinant perithecia were isolated after 7–10 days. For the identification of hybrid perithecia, mutant strains producing black spores were crossed against mutant strains carrying in addition the spore color marker fus1-1. Single spore isolates of selected asci were analyzed by PCR to verify double knock-out strains. Microscopic investigations S. macrospora strains were inoculated on glass slides for 1 to 7 days. Slides were overlaid with BMM or SWG minimal medium as described earlier [18]. Light and fluorescence microscopic investigations were carried out according to Elleuche and Po¨ ggeler [28]. 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