title: Genome scan for nonadditive heterotic trait loci reveals mainly underdominant effects in Saccharomyces cerevisiae.
abstract: The overdominant model of heterosis explains the superior phenotype of hybrids by synergistic allelic interaction within heterozygous loci. To map such genetic variation in yeast, we used a population doubling time dataset of Saccharomyces cerevisiae 16 × 16 diallel and searched for major contributing heterotic trait loci (HTL). Heterosis was observed for the majority of hybrids, as they surpassed their best parent growth rate. However, most of the local heterozygous loci identified by genome scan were surprisingly underdominant, i.e., reduced growth. We speculated that in these loci adverse effects on growth resulted from incompatible allelic interactions. To test this assumption, we eliminated these allelic interactions by creating hybrids with local hemizygosity for the underdominant HTLs, as well as for control random loci. Growth of hybrids was indeed elevated for most hemizygous to HTL genes but not for control genes, hence validating the results of our genome scan. Assessing the consequences of local heterozygosity by reciprocal hemizygosity and allele replacement assays revealed the influence of genetic background on the underdominant effects of HTLs. Overall, this genome-wide study on a multi-parental hybrid population provides a strong argument against single gene overdominance as a major contributor to heterosis, and favors the dominance complementation model.
authors.affiliation: b Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet-Dagan, P.O. Box 6, 50250, Israel.
authors.forename: Efrat
authors.initials: E
authors.lastname: Laiba
authors.affiliation: a The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Faculty of Agriculture, Food, and Environment, The Hebrew University of Jerusalem, 76100 Rehovot, Israel.
authors.forename: Ilana
authors.initials: I
authors.lastname: Glikaite
authors.affiliation: b Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet-Dagan, P.O. Box 6, 50250, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Levy
authors.affiliation: c Department of Plant Pathology and Microbiology, Faculty of Agriculture, Food, and Environment, The Hebrew University of Jerusalem, 76100 Rehovot, Israel.
authors.forename: Zohar
authors.initials: Z
authors.lastname: Pasternak
authors.affiliation: b Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Bet-Dagan, P.O. Box 6, 50250, Israel.
authors.forename: Eyal
authors.initials: E
authors.lastname: Fridman
mesh_terms: D000483:Alleles; D016681:Genome, Fungal; D060005:Genotyping Techniques; D006579:Heterozygote; D006823:Hybrid Vigor; D040582:Inheritance Patterns; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics*
keywords: Saccharomyces cerevisiae; association pan-génomique; genome-wide association; heterosis; hérédité nonadditive; hétérosis; nonadditive inheritance; sous-dominance; underdominance