Opaque cells of <i>C. albicans MTL</i>a/α strains cannot mate with a/a or α/α opaque cells.

<p>10⁶ opaque cells of each mating partner were mixed and spotted onto Lee's GlcNAc agar and incubated at 25°C for 4 days. (A) Patches of <b>a</b>/α cells and <b>a</b>/<b>a</b> or α/α mixture on Lee's GlcNAc medium at 25°C. Three natural <b>a</b>/α isolates were tested. WT<b>a</b>/<b>a</b> (GH1012) and α/α (WO-1) mixture served as a positive control of mating assay. Wrinkle surface indicated the formation of long mating conjugation tubes. (B) Mating response of corresponding patches in panel A. Cell fusion and mating conjugation tubes were only observed in the crosses of (d) and (h). (C) Quantitative mating assay. SZ306u (<i>MTL</i><b>a</b>/α, <i>ura3-</i>), WT<b>a</b> (SN152a, <i>MTL</i><b>a</b>/Δ, <i>arg4-his1-leu2-</i>), WTα (GH1349, a derivative of WUM5A, <i>MTL</i>α/α, <i>agr4-</i>, used for the SZ306u × WTα cross), and WTα (WUM5A, <i>MTL</i>α/α, <i>ura3-</i>, used for the control WTα × WT<b>a</b> cross). Mating efficiency = average ± SD. “<” indicated no prototropic colonies were observed. Opaque cells were used for all the mating crosses.