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We investigated sex chromosome diversity in Zygosaccharomyces rouxii (Z. rouxii). In the current study, we show that the organization of the mating-type (MAT) locus is highly variable in the Z. rouxii population, indicating the MAT, HML, and HMR loci are translocation hotspots. Although NBRC1130 and CBS732 were originally two stocks of the type strain of the species, only NBRC1130 retains the original karyotype. A reciprocal translocation between the MAT and HMR loci appears to have occurred during the early passage culture of CBS732, which was used for genome sequencing. In NBRC1733, NBRC0686, NBRC0740 and NBRC1053, the terminal region of the chromosome containing the HMR locus was replaced with the chromosomal region to the left of the MAT or HML loci. The translocation events found in NBRC1733, NBRC0686, NBRC0740, and NBRC1053 were reconstructed under our experimental conditions using the DA2 background, and the reconstruction suggests that the frequency of this type of translocation is approximately 10−7. These results suggest that the MAT and MAT-like loci were the susceptible regions in the genome, and the diversity of mating-type chromosome structures in Z. rouxii was caused by ectopic exchanges between MAT-like loci.

The mechanism of whole-genome duplication (WGD) in yeast has been intensively studied because it has a large impact on yeast evolution. WGD has shaped the genomic architecture of modern ; however, the mechanism for restoring fertility after interspecies hybridization, which would be involved in the process of WGD, has not been thoroughly elucidated. In this study, we obtained a draft genome sequence of the salt-tolerant yeast NBRC110957 and revealed that it is a hybrid lineage of (allodiploid) with two subgenomes equivalent to NBRC1876. Because this allodiploid yeast can mate with other allodiploid strains and form spores, it can be a good model of restoring fertility after interspecies hybridization. We observed that NBRC110957 and NBRC1876 contain six mating-type-like () loci. There are no large deletions or deleterious mutations in loci, except for several-base-pair deletions in the X region in certain loci. We also assigned only one mating-type (MAT) locus that exclusively determines mating types from six loci. These results suggest that it is possible to recover mating competence regardless of whether cells lose one locus through random gene loss by mitotically dividing after interspecies hybridization. Moreover, we propose that perturbation of gene expression and substantial breakdown of heterozygosity caused by chromosomal rearrangement at loci play roles in restoring the mating competence of allodiploids. This scenario can provide a mechanism for restoring fertility after interspecies hybridization that is compatible with random gene loss models and suggests genomic plasticity during WGD in yeast. A whole-genome duplication occurred in an ancestor of the baker's yeast The origins of this complex and multifaceted process, which requires intra- or interspecies hybridization followed by dysfunction of one mating-type () locus to regain mating competence, has not been thoroughly elucidated. In this study, we provide a mechanism for regaining fertility in an interspecies hybrid, The draft genome sequence analysis and mating test showed that the strain used in this study is an intact interspecies hybrid, suggesting that it is possible to recover fertility regardless of whether cells lose one locus.

To characterize aspartyl aminopeptidase from Aspergillus oryzae, the recombinant enzyme was expressed in Escherichia coli. The enzyme cleaves N-terminal acidic amino acids. About 30% activity was retained in 20% NaCl. Digestion of defatted soybean by the enzyme resulted in an increase in the glutamic acid content, suggesting that the enzyme is potentially responsible for the release of glutamic acid in soy sauce mash.

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Copy number variations (CNVs) contribute to the adaptation process in two possible ways. First, they may have a direct role, in which a certain number of copies often provide a selective advantage. Second, CNVs can also indirectly contribute to adaptation because a higher copy number increases the so-called "mutational target size." In this study, we show that the copy number amplification of FLO11D in the osmotolerant yeast Zygosaccharomyces rouxii promotes its further adaptation to a florformative environment, such as osmostress static culture conditions. We demonstrate that a gene, which was identified as FLO11D, is responsible for flor formation and that its expression is induced by osmostress under glucose-free conditions, which confer unique characteristics to Z. rouxii, such as osmostress-dependent flor formation. This organism possesses zero to three copies of FLO11D, and it appears likely that the FLO11D copy number increased in a branch of the Z. rouxii tree. The cellular hydrophobicity correlates with the FLO11D copy number, and the strain with a higher copy number of FLO11D exhibits a fitness advantage compared to a reference strain under osmostress static culture conditions. Our data indicate that the FLO gene-related system in Z. rouxii has evolved remarkably to adapt to osmostress environments.A N organism adapts to adverse environments to survive and produce progeny. Adaptive evolution is the process through which a population becomes better suited to its environment via mutation, selection, and random drift (Bürger 2000;Cressman 2003;Ewens 2004;Nowak and Sigmund 2004). Types of mutations include nucleotide changes (Steiner et al. 2007;Barrick and Lenski 2009), transposition events (Wilke and Adams 1992;Aminetzach et al. 2005), and copy number variations (CNVs), including gene amplifications (duplication) and deletions (Brown et al. 1998;Perry et al. 2007;Gresham et al. 2010). CNVs can have a phenotypic impact and can consequently alter the fitness of an allele through the following mechanisms: (i) changing the coding sequence of a gene (Yamanaka et al. 2009;Schlattl et al. 2011), (ii) creating paralogs that can diverge from each other and take on new or specialized functions (neofunctionalization or subfunctionalization, respectively) (Ohno 1970;Innan and Kondrashov 2010), and (iii) altering the expression level of a gene (gene dosage effect) (Stranger et al. 2007;Yamanaka et al. 2009;Iskow et al. 2012). In humans, most CNVs overlapping genes are under purifying (negative) selection (Conrad et al. 2010), but a handful of CNVs are thought to be under positive selection (Cooper et al. 2007;Hurles et al. 2010;Iskow et al. 2012) such as AMY1 (Perry et al. 2007). In yeast, there are several examples of how the (increased) copy number can provide a direct selective advantage (Gresham et al. 2008;Voordeckers et al. 2012).In nature, budding yeast exhibits a number of adaptive responses, such as filamentation, invasive growth, flocculation, and biofilm formation, to overcome a deleterious enviro...

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