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

• Main Authors: Dubraska Moreno-Ruiz, Alessandro Fuchs, Kristina Missbach, Rainer Schuhmacher, Susanne Zeilinger
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Pathogens
• Subjects: Trichoderma atroviride; mycoparasitism; secondary metabolites; 6-pentyl-α-pyrone; Tmk3 MAP kinase; light
• Online Access: https://www.mdpi.com/2076-0817/9/10/860

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.