Influence of Different Light Regimes on the Mycoparasitic Activity and 6-Pentyl-α-pyrone Biosynthesis in Two Strains of <i<Trichoderma atroviride</i<

The ascomycete <i<Trichoderma atroviride</i< is well known for its mycoparasitic lifestyle. Similar to other organisms, light is an important cue for <i<T. atroviride.</i< However, besides triggering of conidiation, little is known on the physiological responses of <i<T...
Ausführliche Beschreibung

The ascomycete <i<Trichoderma atroviride</i< is well known for its mycoparasitic lifestyle. Similar to other organisms, light is an important cue for <i<T. atroviride.</i< However, besides triggering of conidiation, little is known on the physiological responses of <i<T. atroviride</i< to light. In this study, we analyzed how cultivation under different light wavelengths and regimes impacted the behavior of two <i<T. atroviride</i< wild-type strains: IMI206040 and P1. While colony extension of both strains was slightly affected by light, massive differences in their photoconidation responses became evident. <i<T. atroviride</i< P1 colonies conidiated under all conditions tested including growth in complete darkness, while IMI206040 required white, blue or green light to trigger asexual reproduction. Interestingly, deletion of the stress-activated MAP kinase-encoding gene <i<tmk3</i< abolished the ability of strain P1 to conidiate in red and yellow light as well as in darkness. Furthermore, light-dependent differences in the mycoparasitic activity and in the biosynthesis of the secondary metabolite 6-pentyl-α-pyrone (6-PP) became evident. 6-PP production was highest upon dark incubation, while light, especially exposure to white light as light/dark cycles, had an inhibitory effect on its biosynthesis. We conclude that the response of <i<T. atroviride</i< to light is strain-dependent and impacts differentiation, mycoparasitism, and 6-PP production; hence, this should be considered in experiments testing the mycoparasitic activity of these fungi. Ausführliche Beschreibung