An avid reader pointed out that I was not entirely thorough in describing that we don’t enough about the V8 agar media that is used to induce mating in Cryptococcus. In fact a great deal of work on mating in this fungus had focused on identifying what pathways are induced by V8 agar that induce mating. It was shown that inositol stimulates mating through use of defined media containing inositol (Xue et al, 2007). This paper interestingly explores plant-fungal interactions and Cryptococcus suggesting that mating may occur preferentially on plants in cases where inositol is abundant.
It is also worth noting that V8 media contains a high level of copper ions and it was also pointed out to me that Jef Edman’s lab showed that melanin mutants have mating defects, and both phenotypes are suppressed by copper. And more recently (Lin et al, PLOS Genetics 2006) found that alleles of the Mac1 copper regulated transcription factor are a QTL influencing hyphal growth and melanin production, and showed that copper can enhance hyphal growth.
So the role of copper and interplay with V8 agar media and how this induces mating is actually quite known.
C XUE, Y TADA, X DONG, J HEITMAN (2007). The Human Fungal Pathogen Cryptococcus Can Complete Its Sexual Cycle during a Pathogenic Association with Plants Cell Host & Microbe, 1 (4), 263-273 DOI: 10.1016/j.chom.2007.05.005