Comparative study ofSaccharomyces cerevisiaewine strains to identify potential marker genes correlated to desiccation stress tolerance

Abstract

The most diffused formulation of starter for winemaking is active dry yeast (ADY). ADYs production process is essentially characterized by air-drying stress, a combination of several stresses, including thermal, hyperosmotic and oxidative and cell capacity to counteract such multiple stresses will determine its survival. The molecular mechanisms underlying cell stress response to desiccation have been mostly studied in laboratory and commercial yeast strains, but a growing interest is currently developing for indigenous yeast strains which represent a valuable and alternative source of genetic and molecular biodiversity to be exploited. In this work, a comparative study of different Saccharomyces cerevisiae indigenous wine strains, previously selected for their technological traits, has been carried out to identify potentially relevant genes involved in desiccation stress tolerance. Cell viability was evaluated along desiccation treatment and gene expression was analyzed by real-time PCR before and during the stress. Our data show that the observed differences in individual strain sensitivity to desiccation stress could be associated to specific gene expression over time. In particular, either the basal or the stress-induced mRNA levels of certain genes, such as HSP12, SSA3, TPS1, TPS2, CTT1 and SOD1, result tightly correlated to the strain survival advantage. This study provides a reliable and sensitive method to predict desiccation stress tolerance of indigenous wine yeast strains which could be preliminary to biotechnological applications.

Identification by phenotypic and genetic approaches of an indigenous Saccharomyces cerevisiae wine strain with high desiccation tolerance

“…Figure reports the fold change in the expression levels of selected genes in SP with respect to EP cells (Capece et al ., ) before desiccation treatment (fresh samples). Only the genes that showed an increase in expression in stationary phase with respect to the exponential phase in at least one of the three strains are shown in Figure .…”

“…In fact, when this strain was compared with another two S. cerevisiae strains, EC1118 (a commercial strain widely used as ADY starter at industrial level) and 5 TB8–60, another indigenous wine strain, it showed the highest tolerance to desiccation treatment and the highest level of expression of certain desiccation‐related genes in stationary growth phase. In a previous work, this strain was selected for its low sensitivity to desiccation in a comparative study of actively dividing indigenous yeast strains undergoing a ‘laboratory dry test’ on a small scale (Capece et al ., ). Here we confirm that S. cerevisiae is more desiccation tolerant during stationary phase than in exponential phase (Ratnakumar and Tunnacliffe, ; Calahan et al ., ).…”

“…Aliquots corresponding to 3 × 10 7 cells were harvested by centrifugation. The cell pellet was washed once, centrifuged again and any residual supernatant was removed by suction, as reported in Capece et al (2016). Each sample was maintained at 37°C in the oven until 24 h. At several time points, samples were taken for evaluation of cell viability; untreated fresh samples were controls.…”

“…In a previous study, an indigenous S. cerevisiae wine strain, namely CD-6Sc, was selected for its higher tolerance to desiccation and higher expression of specific desiccation stress-related genes in comparison with other yeast strains in exponential growth phase (Capece et al, 2016).…”

“…For these reasons, and given that the transcriptional profile of dehydrated cells exhibits analogies with cells in stationary growth phase, in this work stationaryphase cells of previously selected wine strains have been compared for their response to desiccation. Two different drying treatments have been compared: a 'laboratory dry test' on a small scale and a treatment by spray-drying, one of the most appropriate preservation methods for yeast and other micro-organisms (Cañamás et al, 2008;Aponte et al, 2016;Capece et al, 2016). The expression of selected desiccation-related genes has been also assessed in order to validate predictive marker for desiccation tolerance.…”