Polygenic trait’s genetic architecture is complex and all its causative elements are generally unknown. Variability of such a trait also depends on higher order heritability factors. To dissect and assess causative variants for NaCl tolerance as a case of a polygenic trait, we crossed 2 parental haploid yeast strains of large phenotypic difference. We monitored the distribution of the phenotype in a population of their progeny and following 7 generations of backcrossing. After each phenotyping step of a given generation, we selected the offspring strain with the most advanced phenotype.
Analysis of distribution of parental alleles in populations growing in extreme saline and reference conditions allowed us to predict possible causative quantitative trait loci (QTL). On the basis of genomic sequences of the selected segregants we followed the inheritance of predicted quantitative trait loci over the generations.
Inheritance of potential quantitative trait loci, average population phenotype shift and quantitatively assessed phenotype of selected segregants pointed out importance of certain quantitative trait loci. To determine causative elements more toroughly, we provided their relatedness on mechanistic and molecular biology level. Our prediction of novel quantitative trait genes (QTG) is based on heterogeneity and functional relatedness of genes within notable quantitative trait loci. Phenotypic diversity was justified on the basis of predicted structural variants of products of possible causative quantitative trait genes. We presumed potential differences in both role and mechanism of action of protein variants that lead to variability in resistance to NaCl.
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