The formation of atroviridin by Hypocrea atroviridis is conidiation-associated, and positively regulated by blue light and the G-protein GNA3

TU Wien, Institut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften, FB Gentechnik und Angewandte Biochemie, Getreidemarkt 9-166, 1060 Wien, Austria; TU Berlin, Institutfür Chemie, FG Biochemie und Molekulare Biologie Franklinstr. 29, 10587 Berlin, Germany, National Laboratory of Genomics for Biodiversity, Cinvestav Campus Guanajuato, Apartado Postal 629, Irapuato 36500, Mexico, Anagnostec GmbH, Am Mühlenberg 11, 14476, Potsdam, OT Golm, Germany

	Abstract

Species of the mycoparasitic fungal genus Hypocrea/Trichoderma – are prominent producers of peptaibols, a class of small linear peptides of fungal origin. Some of these peptaibols have been shown to act synergistically with cell wall-degrading enzymes in the inhibition of the growth of other fungi in vitro and in vivo. Here we present the structure of the H. atroviridis peptaibol synthetase gene (pbs1), deduced from the genome sequence of H. atroviridis. It consists of 19 typical peptide synthetase modules with the required additional modifying domains at the N- and C-termini. Phylogenetic and similarity analyses of the individual amino acid activating modules is consistent with its ability to synthesize atroviridins. MALDI-TOF mass spectrometry of surface grown cultures of H. atroviridis showed that no peptaibols were formed during vegetative growth, but a microheterogenous mixture of atroviridins accumulated when the colonies started to sporulate. This correlation between sporulation and atroviridin formation was shown to be independent of the pathway inducing sporulation (i.e. light, mechanical injury and carbon starvation, respectively). Atroviridin formation was dependent on the function of the two blue light regulators BLR1 and BLR2 under some but not all conditions of sporulation, and was repressed in a pkr1-(regulatory subunit of protein kinase A) antisense strain with constitutively active protein kinase A. Conversely, however, loss of function of the G-protein GNA3, which is a negative regulator of sporulation and leads to a hypersporulating phenotype, fully impairs atroviridin formation. Our data show that formation of atroviridin by H. atroviridis occurs in a sporulation-associated manner, but is uncoupled from it at the stage of GNA3.