Small heat-shock protein Hsp12 contributes to yeast tolerance to freezing stress

Abstract

The HSP12 gene encodes one of the two major small heat-shock proteins of Saccharomyces cerevisiae and is induced under different conditions, such as low and high temperatures, osmotic or oxidative stress and high sugar or ethanol concentrations. However, few studies could demonstrate any correlation between HSP12 deletion or overexpression and a phenotype of sensitivity/resistance, making it difficult to attribute a role for Hsp12p under several of these stress conditions. We investigated the possible role of Hsp12p in yeast freezing tolerance. Contrary to what would be expected, the hsp12 null mutant when subjected to prolonged storage at "20 6C showed an increased resistance to freezing when compared with the isogenic wild-type strain. Because the mutant strain displayed a higher intracellular trehalose concentration than the wildtype, which could mask the effect of manipulating HSP12, we overexpressed the HSP12 gene in a trehalose-6-phosphate synthase (TPS1) null mutant. The tps1D strain overexpressing HSP12 showed an increase in resistance to freezing storage, indicating that Hsp12p plays a role in freezing tolerance in a way that seems to be interchangeable with trehalose. In addition, we show that overexpression of HSP12 in this tps1D strain also increased resistance to heat shock and that absence of HSP12 compromises the ability of yeast cells to accumulate high levels of trehalose in response to a mild heat stress. INTRODUCTIONBecause freezing is one of the major abiotic stresses, the adaptation mechanisms that preserve cells at subzero temperatures are extremely important in the development of technology for the cryopreservation of life. Preservation of cell activity is also a very important issue in frozendough technology. This process is well established in the modern baking industry, as it can more easily supply ovenfresh bakery products to consumers while improving labour conditions. Nevertheless, storage of frozen bread dough may lead to the loss of cell viability of baker's yeast as well as of its baking capacity, and consequently to economic losses (Alves-Araú jo et al., 2004;Randez-Gil et al., 1999). In spite of their importance, limited information is available about the mechanisms and determinants of freezing resistance and cold responses in yeast (Kandror & Goldberg, 1997;Kandror et al., 2004;Odani et al., 2003;Zarka et al., 2003). When yeast cells are cultured at 4 u C for a long period, several heat-shock proteins (HSPs) are induced (Homma et al., 2003), suggesting that the induction of these genes might be necessary for adjustment to cold resistance. Considerable evidence indicates that the intracellular level of trehalose may determine the survival response of yeasts under extreme environmental conditions (Diniz-Mendes et al., 1999;Hottiger et al., 1987;Singer & Lindquist, 1998;Van Dijck et al., 1995;Wiemken, 1990). In general, there is wide consensus that trehalose can serve as a stress protectant when yeast cells are confronted with high or low temperatures (Attfield, 1987;Hottiger et ...

Proteome analysis of the farnesol-induced stress response in Aspergillus nidulans—The role of a putative dehydrin

“…However, until now this protein family has hardly been investigated in fungi. In T. borchii and in yeast, several dehydrin-like proteins (Hsp12, Gre1, Sip18) have been described previously [43][44][45][46][47]. Recently, Wong Sak Hoi et al [34,35] identified three dehydrins (DprA, DprB and DprC) in the A. fumigatus genome that contribute to the protection against high pH, freezing, osmotic and oxidative stress.…”

Conserved Motifs in the Msn2-Activating Domain are Important for Msn2-Mediated Yeast Stress Response

“…S3) (Pacheco et al, 2009;Welker et al, 2010). The HSP12 promoter contains several stress response elements (STRE) and was shown to be strongly induced following yeast exposure to diverse stress conditions (Martínez-Pastor et al, 1996;Pacheco et al, 2009). We have recently found that Hsp12 expression levels are tightly correlated to the expression of other Msn2 reporter genes, including PNC1 and TPS2, and to yeast stress survival, showing that HSP12 reporter gene can reflect overall Msn2 transcriptional activity (Sadeh et al, 2011).…”

“…HSP12 is a general stress response gene encoding a plasma membrane protein and its expression is highly dependent upon Msn2/4 transcriptional activity (supplementary material Fig. S3) (Pacheco et al, 2009;Welker et al, 2010). The HSP12 promoter contains several stress response elements (STRE) and was shown to be strongly induced following yeast exposure to diverse stress conditions (Martínez-Pastor et al, 1996;Pacheco et al, 2009).…”

Characterization of Small HSPs from Anemonia viridis Reveals Insights into Molecular Evolution of Alpha Crystallin Genes among Cnidarians

“…The accumulation of sHSPs is considered part of the mechanisms responsible for tolerance to cold-stress injury in several organisms [61], [62]. The cold stress also induced a quick expression of AvHSP28.6 in sea anemone.…”