Abstract
The pathogenic fungus Cryptococcus neoformans uses the Bwc1-Bwc2 photoreceptor complex to regulate mating in response to light, virulence and ultraviolet radiation tolerance. How the complex controls these functions is unclear. Here, we identify and characterize a gene in Cryptococcus, UVE1, whose mutation leads to a UV hypersensitive phenotype. The homologous gene in fission yeast Schizosaccharomyces pombe encodes an apurinic/apyrimidinic endonuclease acting in the UVDE-dependent excision repair (UVER) pathway. C. neoformans UVE1 complements a S. pombe uvde knockout strain. UVE1 is photoregulated in a Bwc1-dependent manner in Cryptococcus, and in Neurospora crassa and Phycomyces blakesleeanus that are species that represent two other major lineages in the fungi. Overexpression of UVE1 in bwc1 mutants rescues their UV sensitivity phenotype and gel mobility shift experiments show binding of Bwc2 to the UVE1 promoter, indicating that UVE1 is a direct downstream target for the Bwc1-Bwc2 complex. Uve1-GFP fusions localize to the mitochondria. Repair of UV-induced damage to the mitochondria is delayed in the uve1 mutant strain. Thus, in C. neoformans UVE1 is a key gene regulated in response to light that is responsible for tolerance to UV stress for protection of the mitochondrial genome.
Highlights
The ability to sense light provides well-known advantages to organisms, such as adapting to photosynthetic light sources in plants and for vision in animals, yet the benefits of light-sensing in non-photosynthetic and non-motile organisms are less established
UVE1 is essential in C. neoformans for survival under UV stress
The UVE1 complemented strain completely rescued the UV sensitivity phenotype (Figure 1). These results show that in C. neoformans the UVE1 gene is required for survival under UV stress
Summary
The ability to sense light provides well-known advantages to organisms, such as adapting to photosynthetic light sources in plants and for vision in animals, yet the benefits of light-sensing in non-photosynthetic and non-motile organisms are less established. Light influences different responses in different fungi, including phototropism, induction of pigmentation, asexual and sexual sporulation, changes is primary and secondary metabolism, and regulating the circadian clock: most of which are controlled, where established, by the WCC [1,2,3]. A major question is what advantage is provided in using light as an environmental signal to regulate these processes. One compelling hypothesis is that protecting DNA from damage provides a selective pressure, and that wavelengths in the visible spectrum are sensed to indicate the presence of deleterious ultraviolet radiation. A DNA repair system common to light-sensing fungi and that acts directly downstream of the WCC is unknown to date
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