FIG. 6.

Model for the regulation of sexual development in C. neoformans. Model for the role of Sxi1α and Sxi2a in controlling sexual development. Large ovals represent cells. A solid circle represents the a nucleus, and a hatched blue circle represents the α nucleus. The yellow oval X and shaded blue square Y represent unknown a- and α-specific factors, respectively, that lead to the induction of SXI1α and SXI2a. The blue shaded oval represents Sxi1α, and the yellow star represents Sxi2a. (Top) SXI1α and SXI2a are expressed at low levels in haploid cells. (Middle) Following cell fusion, SXI1α and SXI2a expression is dependent upon and induced by factors from both a and α cells (X and Y). (Bottom) After induction, Sxi1α and Sxi2a form a heterodimeric complex that establishes the dikaryotic state and induces sexual development through the repression of mating genes.