Enhanced stability of YEp plasmids in lager brewing yeasts is related to lager brewing yeast 2-microns DNA

An efficient method for isolating mating-competent cells from bottom-fermenting yeast using mating pheromone-supersensitive mutants

Crossbreeding is an effective approach to construct novel yeast strains with preferred characteristics; however, it is difficult to crossbreed strains of brewer's yeast, especially the bottom-fermenting yeast Saccharomyces pastorianus, because of the relative inefficiency of the available methods to obtain mating-competent cells (MCCs). Here, we describe a productive method for the isolation of MCCs without artificial genetic modification. We focused on the characteristics of two mating pheromone-supersensitive mutants, Δbar1 and Δsst2, that show a growth defect in the presence of the mating pheromone. When MCCs secreting α-factor and a-factor were spotted on to a lawn of MATa Δbar1 and MATα Δsst2, a halo was observed around the respective MCCs. This plate assay was successful in identifying MCCs from bottom-fermenting yeast strains. Furthermore, by selecting for cells that caused the growth defect in pheromone-supersensitive cells on cultures plates, 40 α/α-type and six a/a-type meiotic segregants of bottom-fermenting yeast strains were successfully isolated and crossed with tester strains to verify their mating type. This method of isolation is expected to be applicable to other industrial yeast strains, including wine, sake and distiller's yeasts, and will enable MCCs without genetic modifications to be obtained. As a result, it will be a useful tool for more convenient and efficient crossbreeding of industrial yeast strains that can be applied to practical brewing. Copyright © 2017 John Wiley & Sons, Ltd.

Vectors designed for efficient molecular manipulation in Candida albicans

Functional studies on genes of Candida albicans have been hampered by the fact that few vectors are available for efficient cloning and expression in C. albicans, in contrast to Saccharomyces cerevisiae. Here we report that six vectors were constructed for molecular manipulation in C. albicans. All of them contained the autonomous replicating sequence ARS2 and the uracil gene as a selective marker. Introduction of multicloning site (MCS) facilitated directional cloning into various convenient restriction sites is discussed. Distal to the MCS, the additions of sequences encoding yeast-enhanced green fluorescent protein 3 (yEGFP3) and the terminator of chitin synthase 2 (TCHS2) enabled us to express an open reading frame (ORF) with its own promoter as a GFP fusion protein, so that its intracellular localization could be easily determined. A vector of 7.4 kb was also constructed to express a cloned ORF as a GFP fusion protein under the control of an inducible MET3 promoter (PMET3) located proximal to the MCS. Since this vector was relatively large in size for expressing ORFs, two additional vectors of 6.7 kb were constructed by inserting PMET3 and TCHS2 proximal and distal to the MCS of the above vector containing MCS only, respectively. These six vectors made it possible to study C. albicans in greater detail. They can be used in identification of a promoter, intracellular localization of a protein, and in the induction of lethal genes.