A sexual interaction was discovered between two strains of Rhodotorula glutinis considered as haploid. The nutritionally prototrophic mycelial colony was obtained by the conjugation and plasmogamy of cells of their auxotrophic mutants. The mycelial development was also found in the couple of their wild type cells. The mycelium has septa with clamp-connections, and consists of dikaryotic cells. It produces terminally brown pear-shaped resting spores which are regarded as diploid. The resting spore germinates to form a promycelium, on which haploid sporidia bud off laterally. Single sporidium propagates by budding and develops to the same haploid yeast as that of the original Rhodotorula strains.Among monosporidial yeasts, there are two mating types. The same mycelial stage appears again by conjugation of the two mating types. For the perfect stage of these strains of Rhodotorula, a life history is proposed schematically. It was concluded that this organism was related to the order Ustilaginales of Basidiomycetes.After the examination for sexual interaction in many couples of the authentic strains of Rhodotorula, the same mating reactions were found between IFO. 0559, IFO. 0413, or IFO. 0871 and IFO. 0880 or IFO.1236. The mating types of the former three and the latter two were designated by symbols A and a, respectively.A monotypic new genus, Rhodosporidium, was proposed and a new species, Rhodosporidium toruloides, was given to the perfect stage of these Rhodotorula strains.Rhodotorula, a well-known red yeast genus, has been studied taxonomically since FRESENIUS (1) described in 1852 the first red yeast under the name of Cryptococcus glutinis.The present genus has been regarded as a member of the Fungi Imperfecti, but BANNO (2) reported preliminarily on the cell conjugation and mycelial stage in two Rhodotorula yeasts. The present paper describes the details of a research on the sexuality and the life cycle of some Rhodotorula yeasts. MATERIALS AND METHODS Microorganisms.Two strains, IFO. 0559 and 0880 of Rhodotorula glutinis, were mainly used. The former was isolated from a wood-pulp and 167

The structural gene, PHO13, for the specific p-nitrophenyl phosphatase of Saccharomyces cerevisiae was cloned and its nucleotide sequence determined. The deduced PHO13 protein consists of 312 amino acids and its molecular weight is 34635. The disruption of the PHO13 gene produced no effect on cell growth, sporulation, or viability of ascospores. The PHO13 locus was mapped at 1.9 centimorgans from the HO locus on the left arm of chromosome IV. By chromosome fragmentation, the PHO13 locus was found to be located about 72 kb from the left-hand telomere of chromosome IV and distal to the HO locus.

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