Author/Editor		Marinoni, Gaealle; Piškur, Jure; Lachance, Marc-Andre
Title		Ascospores of large-spored Metschnikowia species are genuine meiotic products of these yeasts
Type		članek
Source		FEMS Yeast Res
Vol. and No.		Letnik 3, št. 1
Publication year		2003
Volume		str. 85-90
Language		eng
Abstract		The asci of Metschnikowia species normally contain two ascospores (never more), raising the question of whether these spores are true meiotic products. We investigated this problem by crossing genetically-marked strains of the haploid, heterothallic taxa Metschnikowia hawaiiensis, Metschnikowia continentalis var. continentalis, and M. continentalis var. borealis. Asci were dissected and the segregation patterns for various phenotypes analyzed. In all cases (n = 47) both mating types (h+ and h-) were recovered in pairs of sister spores, casting further uncertainty as to whether normal meiosis takes place. However, the segregation patterns for cycloheximide resistance and several auxotrophic markers were random, suggesting that normal meiosis indeed occurs. To explain the lack of second-division segregation of mating types, we concluded that crossing-over does not occur between the mating-type locus and the centromere, and that meiosis I is tied to spore formation, which explains why the number of spores is limited to two. The latter assumption was also supported by fluorescence microscopy. The second meiotic division takes place inside the spores and is followed by the resorption of two nuclei, one in each spore.
Descriptors		CROSSES, GENETIC DIPLOIDY MEIOSIS MICROSCOPY, FLUORESCENCE MUTAGENESIS PHENOTYPE RECOMBINATION, GENETIC SPORES, FUNGAL