Uptake of inorganic phosphate is a limiting factor for Saccharomyces cerevisiae during growth at low temperatures.
The fermenting ability of Saccharomyces at low temperatures is crucial for the development of alcoholic beverages, but the key factors for the cold tolerance of yeast are not well known. In this report, we present the results of a screening for genes able to confer cold tolerance by overexpression in a laboratory yeast strain auxotrophic for tryptophan. We identified genes of tryptophan permeases (TAT1 and TAT2), suggesting that the first limiting factor in the growth of tryptophan auxotrophic yeast at low temperatures is tryptophan uptake. This fact is of little relevance to industrial strains which are prototrophic for tryptophan. Then, we screened for genes able to confer growth at low temperatures in tryptophan-rich media and found several genes related to phosphate uptake (PHO84, PHO87, PHO90 and GTR1). This suggests that without tryptophan limitation, uptake of inorganic phosphate becomes the limiting factor. We have found that overexpression of the previously uncharacterized ORF YCR015c/CTO1 increases the uptake of inorganic phosphate. Also, genes involved in ergosterol biosynthesis (NSG2) cause improvement of growth at 10°C, dependent on tryptophan uptake, while the gluconeogenesis gene PCK1 and the proline biosynthesis gene PRO2 cause an improvement in growth at 10°C, independent of tryptophan and phosphate uptake.
Instituto de Universitario de Ingeniería de Alimentos para el Desarrollo. Universidad Politécnica de Valencia, 46022 Valencia, Spain.
Isabel
I
Vicent
Instituto de Universitario de Ingeniería de Alimentos para el Desarrollo. Universidad Politécnica de Valencia, 46022 Valencia, Spain.
Alfonso
A
Navarro
Instituto de Biología Molecular y Celular de Plantas. Universidad Politecnica de Valencia- Consejo Superior de Investigaciones Científicas, 46022 Valencia, Spain jmmulet@ibmcp.upv.es.
Jose M
JM
Mulet
Department of Biochemistry, Panjab University, 160014 Chandigarh, India.
Sukesh
S
Sharma
Instituto de Biología Molecular y Celular de Plantas. Universidad Politecnica de Valencia- Consejo Superior de Investigaciones Científicas, 46022 Valencia, Spain.
Ramón
R
Serrano
D000434:Alcoholic Beverages / Q000382:microbiology; D003080:Cold Temperature; D010710:Phosphates / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000254:growth & development* / Q000378:metabolism* / Q000528:radiation effects
D010710:Phosphates
CTO1; cold stress; phosphate transport; tryptophan uptake