On the complexity of the Saccharomyces bayanus taxon: hybridization and potential hybrid speciation.
Although the genus Saccharomyces has been thoroughly studied, some species in the genus has not yet been accurately resolved; an example is S. bayanus, a taxon that includes genetically diverse lineages of pure and hybrid strains. This diversity makes the assignation and classification of strains belonging to this species unclear and controversial. They have been subdivided by some authors into two varieties (bayanus and uvarum), which have been raised to the species level by others. In this work, we evaluate the complexity of 46 different strains included in the S. bayanus taxon by means of PCR-RFLP analysis and by sequencing of 34 gene regions and one mitochondrial gene. Using the sequence data, and based on the S. bayanus var. bayanus reference strain NBRC 1948, a hypothetical pure S. bayanus was reconstructed for these genes that showed alleles with similarity values lower than 97% with the S. bayanus var. uvarum strain CBS 7001, and of 99-100% with the non S. cerevisiae portion in S. pastorianus Weihenstephan 34/70 and with the new species S. eubayanus. Among the S. bayanus strains under study, different levels of homozygosity, hybridization and introgression were found; however, no pure S. bayanus var. bayanus strain was identified. These S. bayanus hybrids can be classified into two types: homozygous (type I) and heterozygous hybrids (type II), indicating that they have been originated by different hybridization processes. Therefore, a putative evolutionary scenario involving two different hybridization events between a S. bayanus var. uvarum and unknown European S. eubayanus-like strains can be postulated to explain the genomic diversity observed in our S. bayanus var. bayanus strains.
Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos (CSIC), València, Spain.
Laura
L
Pérez-Través
Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos (CSIC), València, Spain; Grupo de Biodiversidad y Biotecnología de Levaduras, Instituto Multidisciplinario de Investigación y Desarrollo de la Patagonia Norte (IDEPA), CONICET-UNCo, Departmento Química, Facultad de Ingeniería, Universidad Nacional del Comahue, Buenos Aires, Neuquén, Argentina.
Christian A
CA
Lopes
Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos (CSIC), València, Spain.
Amparo
A
Querol
Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos (CSIC), València, Spain; Departament de Genètica, Universitat de València, València, Spain.
Eladio
E
Barrio
D001483:Base Sequence; D016000:Cluster Analysis; D049810:Genetic Speciation; D014644:Genetic Variation; D005828:Genetics, Population; D006824:Hybridization, Genetic / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012440:Saccharomyces / Q000145:classification* / Q000235:genetics*; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D013045:Species Specificity