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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Microbiol. | doi: 10.3389/fmicb.2019.01686

KAE1 allelic variants affect TORC1 activation and fermentation kinetics in Saccharomyces cerevisiae

  • 1Department of Food Science and Technology, Technological Faculty, University of Santiago, Chile, Chile
  • 2Center for Studies in Food Science and Technology, University of Santiago, Chile, Chile
  • 3Millennium Institute for Integrative Biology (iBio), Chile
  • 4Biozentrum, Universität Basel, Switzerland
  • 5Instituto de Agroquímica y Tecnología de Alimentos (IATA), Spain
  • 6Department of Molecular Genetics and Microbiology, Faculty of Biological Sciences, Pontifical Catholic University of Chile, Chile

The eukaryotic domain-conserved TORC1 signalling pathway connects growth with nutrient sufficiency, promoting anabolic processes such as ribosomal biogenesis and protein synthesis. In Saccharomyces cerevisiae, TORC1 is activated mainly by the nitrogen sources. Recently, this pathway has gotten renewed attention but now in the context of the alcoholic fermentation, due to its key role in nitrogen metabolism regulation. Although the distal and proximal effectors downstream TORC1 are well characterized in yeast, the mechanism by which TORC1 is activated by nitrogen sources is not fully understood. In this work, we took advantage of a previously developed microculture-based methodology, which indirectly evaluates TORC1 activation in a nitrogen upshift experiment, to identify genetic variants affecting the activation of this pathway. We used this method to phenotype a recombinant population derived from two strains (SA and WE) with different geographic origins, which show opposite phenotypes for TORC1 activation by glutamine. Using this phenotypic information, we performed a QTL mapping that allowed us to identify several QTLs for TORC1 activation. Using a reciprocal hemizygous analysis, we validated GUS1, KAE1, PIB2 and UTH1 as genes responsible for the natural variation in the TORC1 activation. We observed that reciprocal hemizygous strains for KAE1 (ATPase required for t6A tRNA modification) gene showed the greatest phenotypic differences for TORC1 activation, with the hemizygous strain carrying the SA allele (KAE1SA) showing the higher TORC1 activation. In addition, we evaluated the fermentative capacities of the hemizygous strains under low nitrogen conditions, observing an antagonistic effect for KAE1SA allele, where the hemizygous strain containing this allele presented the lower fermentation rate. Altogether, these results highlight the importance of the tRNA processing in TORC1 activation and connects this pathway with the yeasts fermentation kinetics under nitrogen-limited conditions.

Keywords: Saccharomyces cerevisiae, TORC1 pathway, natural variation, Microculture, Fermentation, TRNA modification

Received: 04 Mar 2019; Accepted: 09 Jul 2019.

Edited by:

Joaquin Bautista-Gallego, Instituto de la Grasa (IG), Spain

Reviewed by:

Ricardo Franco-Duarte, University of Minho, Portugal
Daisuke Watanabe, Nara Institute of Science and Technology (NAIST), Japan  

Copyright: © 2019 Kessi-Pérez, Salinas, González, Su, Guillamón, Hall, Larrondo and Martinez. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Claudio Martinez, Department of Food Science and Technology, Technological Faculty, University of Santiago, Chile, Santiago, Santiago Metropolitan Region (RM), Chile, Claudio.martinez@usach.cl