Abstract
The ascomycete Trichoderma atroviride is well known for its mycoparasitic lifestyle. Similar to other organisms, light is an important cue for T. atroviride. However, besides triggering of conidiation, little is known on the physiological responses of T. atroviride to light. In this study, we analyzed how cultivation under different light wavelengths and regimes impacted the behavior of two T. atroviride 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. T. atroviride 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 tmk3 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 T. atroviride 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.
Highlights
The mycoparasitic fungus Trichoderma atroviride is applied in agriculture to protect plants against a variety of fungal pathogens
Much of our knowledge on fungal mycoparasitism comes from studies with T. atroviride, of which two strains are frequently used as model organisms: T. atroviride IMI206040, a strain isolated from a plum tree in an orchard in southern Sweden, and T. atroviride P1 (ATCC 74058), a fungicide resistant isolate from the UK
We provide data on their light-dependent radial growth, conidiation behavior, and mycoparasitic activities as well as the influence of the different light regimes on the production of 6-pentyl-α-pyrone (6-PP), one of the main antifungal secondary metabolites derived from T. atroviride
Summary
The mycoparasitic fungus Trichoderma atroviride is applied in agriculture to protect plants against a variety of fungal pathogens. Much of our knowledge on fungal mycoparasitism comes from studies with T. atroviride, of which two strains are frequently used as model organisms: T. atroviride IMI206040, a strain isolated from a plum tree in an orchard in southern Sweden, and T. atroviride P1 (ATCC 74058), a fungicide resistant isolate from the UK. Both T. atroviride strains are known as producers of. 6-pentyl-α-pyrone (6-PP), a strongly antifungal secondary metabolite, which shows plant-growth promoting characteristics, in a concentration-dependent manner.
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