Fig. 1.

Scheme of identification of causative genes linked to the thermotolerance phenotype. One superior thermotolerant strain ScY01 and one inferior thermosensitive strain W65 were selected from 124 S. cerevisiae strains based on evaluation of thermotolerance. The haploid segregants of two parent strains with HO gene deletion were generated and crossed to create the hybrid diploid strain tp/sp. Total 277 segregants were sporulated from the hybrid strain and selected for the superior, random and inferior pools based on evaluation of thermotolerance. Genomic DNA was extracted from these three pools as well as two parent strains and the best and worst spores in the superior pool and subjected to genome resequencing. QTL mapping analyses were performed using the EXPloRA and MULTIPOOL methods. To identify candidate causative genes, the SNPs in QTLs were annotated, and the nonsynonymous SNPs in coding regions were sorted out according to their existences in G28 and Z118 and their manually checked frequencies using Integrative Genomics Viewer (IGV). Two major QTLs and two minor QTLs were identified to originate from the superior and inferior parent strain, in which five and three genes contained nonsynonymous single nucleotide polymorphism (SNP) variants, respectively. Reciprocal hemizygosity analysis (RHA) and allele replacement analysis further revealed two causative genes in major QTLs and one causative gene in minor QTLs