Abstract
Light provides critical information for the behavior and development of basically all organisms. Filamentous fungi sense blue light, mainly, through a unique transcription factor complex that activates its targets in a light-dependent manner. In Trichoderma atroviride, the BLR-1 and BLR-2 proteins constitute this complex, which triggers the light-dependent formation of asexual reproduction structures (conidia). We generated an ENVOY photoreceptor mutant and performed RNA-seq analyses in the mutants of this gene and in those of the BLR-1, CRY-1 and CRY-DASH photoreceptors in response to a pulse of low intensity blue light. Like in other filamentous fungi BLR-1 appears to play a central role in the regulation of blue-light responses. Phenotypic characterization of the Δenv-1 mutant showed that ENVOY functions as a growth and conidiation checkpoint, preventing exacerbated light responses. Similarly, we observed that CRY-1 and CRY-DASH contribute to the typical light-induced conidiation response. In the Δenv-1 mutant, we observed, at the transcriptomic level, a general induction of DNA metabolic processes and strong repression of central metabolism. An analysis of the expression level of DNA repair genes showed that they increase their expression in the absence of env-1. Consistently, photoreactivation experiments showed that Δenv-1 had increased DNA repair capacity. Our results indicate that light perception in T. atroviride is far more complex than originally thought.
Highlights
Light is an environmental clue for the behavior, development, and physiology of living beings, they have developed sophisticated mechanisms to perceive and respond to the quality, quantity, and direction of this stimulus
We evaluated the effect of continuous exposure to white light on colony growth of the wild type strain (WT) strain of T. atroviride, and the blr-1, env1, cry-DASH and cry-1 mutants in potato dextrose agar (PDA)
These results indicate that ENVOY plays an important role in regulating growth under constant illumination in T. atroviride
Summary
Light is an environmental clue for the behavior, development, and physiology of living beings, they have developed sophisticated mechanisms to perceive and respond to the quality, quantity, and direction of this stimulus. The energy of light is perceived by the photoreceptors, leading to the adoption of an active state of the protein (Chen et al, 2004; Ko et al, 2007). Fungi use light as a source of information about the environment that surrounds them. Due to their relative simplicity, filamentous fungi have been used as models to understand the mechanisms of light perception. Among the responses mediated by light in filamentous fungi are conidiation, phototropism, sexual development, entrainment of the circadian rhythm, photomorphogenesis and secondary metabolism (Herrera-Estrella and Horwitz, 2007; Rodríguez-Romero et al, 2010). It is known that there are responses regulated by green, red and ultraviolet light, blue light regulates most responses in fungi (Herrera-Estrella and Horwitz, 2007)
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