The melanin synthesis is positively regulated by alpha-MSH hormone secreted by the pituitary gland. Further, the modification of POMC is essential for both pituitary gland cells and peripheral skin cells to produce and secrete alpha-MSH and endorphin. Given these phenomena are kept in the long evolution context, the light-sensitive mammals and even the lower animals benefit from melanin synthesis to protect themselves from UV-induced DNA damage.  

Thanks for your answer, I am looking for something specific to fungi

In fungi, melanin biosynthesis is related to several issues, such infectiviry, formation of fruit bodies, greater resistance of cell walls and resistance against host toxins.

There are some reviews concerning your interest. Just to start with, 

Fungal melanins: a review, M J Butler, A W Day. Canadian Journal of Microbiology, 1998, 44(12): 1115-1136.

Melanin and virulence in Cryptococcus neoformans. Arturo Casadevall, , Angel L Rosas, Joshua D Nosanchuk. Current Opinion in Microbiology, 3, 2000, 354-358

 Thank you very much for your interest, I read many paper concerning melanin and melanin biosynthesis but I can not catch how is melanin evolute in fungi? I found information about melanin evolution in human but not in fungi.

Regard