Pheromone systems are essential to determining mating compatibility even in fungi that also exhibit anisogamy; the determination of gamete morphology is very rarely linked to molecular mating types (Billiard et al., 2011).
Using tester strains with good mating abilities and five asexual strains for which the molecular determination of mating type had been obtained, we repeated crosses and confirmed that these strains do not mate in culture.
For determination of mating type, all plasmids were removed via cultivation in YPD medium to yield strains K76A and K76AL (Table 1).
In oomycetes, SSRs have had important applications such as diagnosis and determination of mating type [ 13], genetic structure and disease dynamics [ 14, 15], and population genetics [ 16, 17].
Consistent with other Ascomycota, our expression data suggest that MAT1-1 and MAT1-2 are likely responsible for determination of mating type, because the precursor to α-pheromone (ppg1) was only expressed in the MAT1-1 background.
In fungi, however, the haploid determination of mating compatibility creates the distinction that pseudoautosomal regions would be under more frequent selection to maintain this homolog-pairing role during every meiosis, rather than in just half of meioses, because there is no homogametic diploid.
More precise determination of the mating projection direction was aided by using the fluorescent dye ConA-Alexa-488 to label the growing projection; this dye did not perturb the directional sensing (Supporting Information, Fig. S2).
Determination of the mating type was done by PCR and pheromone assay.
For chromosomal sex determination systems, cross-mating should yield an approximately 1 1 ratio of males to hermaphrodites.
