Resolution of quantitative trait loci for tolerance to acetic acid in Saccharomyces cerevisiae through meiotic reversal

Author(s)

Monique Furlan

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2021-05-19

Examining board members

Gonçalo Amarante Guimarães Pereira; Sandra Regina Ceccato Antonini; João Paulo Lourenço Franco Cairo

• Advisor: Gonçalo Amarante Guimarães Pereira; Elizabeth Bilsland

Abstract

During the first and second generation bioethanol production steps, yeasts need to be tolerant to the acetic acid present in the process, which causes a decrease in the ethanol production rate and can even cause cell death. Tolerance to this acid is a quantitative characteristic that occurs through the interaction of a set of proteins. To find out which they are, as well as which single nucleotide polymorphisms (SNPs) are present in their coding genes, the Quantitative Trait Loci (QTL) mapping methodology is widely used in the scientific community. However, it requires (i) a high homogeneity of the population and (ii) a large number of haploids for (iii) an analysis of extreme phenotypes, which can cause loss of information about intermediate phenotypes. The collection of a large number of haploids can happen through manual dissection of tetrads or high-throughput methods using flow cytometry. However, they require a long time to collect haploids, phenotype them and final crosses. This time problem can be solved through Meiotic Reversion (RTG), in which you can obtain diploids already recombined. To solve the problem of analysis only of extreme phenotypes, a methodology of analysis by tolerance in different strata is proposed. Therefore, the aim goal of this project is to reveal the molecular bases involved in the tolerance to acetic acid in Sacchamonyces cerevisiae, using strata analysis and RTG with cell cycle synchrony. As a result, different SNPs selection patterns were found for the intermediate and good strains, some of which appear more important for the intermediate strain and others for the good. The functions of the genes that contained them include cell cycle, cell polarization, amino acid synthesis, intracellular traffic, stress and glycolytic and acetate consumption pathways, which are closely related to the damage that acetic acid causes inside the cell. There was no overlap of genes found for each of the strata analyzed and an enrichment of genes related to protein synthesis was observed for the intermediate strain, while for the good, enrichment for genes related to the cell cycle, both in its structural part and regulatory. Thus, it is concluded that the tolerance for acetic acid is due to a complex genetic architecture that allows the yeast to bypass the challenges imposed by the compound inside the cell (AU)

• FAPESP's process: 19/14071-3 - Development of an approach for selection of recombinant diploid based on cell cycle synchronization in Saccharomyces cerevisiae
• Grantee: Monique Furlan
• Support Opportunities: Scholarships in Brazil - Master