Responses of grapevine cells to physiological doses of ethanol, among which induced resistance to heat stress

Grapevine is a plant of agronomic interest, which is able to cope with several stresses: heat, drought, and hypoxia, among others. A recent study showed very low oxygen levels inside grape berries, linked to ethanol content. Other studies have established the link between ethanol and tolerance to various stresses: heat stress, drought, and high salinity. The causes of such tolerance induced by ethanol are not well understood. In our study, three-week-old Gamay calli were characterised for their endogenous O2 levels (78 ± 43 µM at 2.1 mm inside the callus) and endogenous ethanol concentration (406 ± 2 µM). Subsequently, a transcriptomic study of these cells was conducted, at 6 and 24 hours post-treatment with 1 mM ethanol. After 6 hours post-treatment, ethanol addition led to 386 Differentially Expressed Genes (DEGs) compared to the controls. Analyses of the gene classes modulated by ethanol showed that many genes involved in heat response were up-regulated, notably the small Heat Shock Proteins (sHSP). Next, we showed that grape cells primed with ethanol experienced less pigment leakage due to heat stress compared to the controls. This result was further supported by a similar observation in Arabidopsis seedlings, for which heat stress-induced electrolyte leakage was reduced by ethanol priming. his study confirms previous observations regarding the beneficial role of ethanol priming in protecting plants against heat stress and provides a comprehensive set of RNA-seq data to further decipher the mechanisms involved in such adaptation. The small heat shock proteins seem involved in this chemical priming response. Overall design: To identify the molecular pathways differentially regulated by a physiological dose of ethanol in Vitis vinifera (cv. Gamay Fréaux var. Teinturier) cell cultures, we carried out a genome-wide transcriptomic analysis by RNA-seq. RNA was extracted from grapevine calli treated with 100 µL of either a 1 mM ethanol solution or a control solution. Prior to treatment, the grapevine cell cultures were grown for three weeks under controlled conditions, with a 16-hour day/8-hour night photoperiod, temperatures of 25°C during the day and 20°C at night, and a light intensity of 150 µmol/m²/s. Samples were collected at either 6 or 24 hours after the control or ethanol treatment.