Physiological characterization of drought stress response and expression of two transcription factors and two LEA genes in three Prunus genotypes

Global warming has led to a progressive decrease in rainfall, which is reflected by a reduction of water resources in the soil and a negative effect on crop production in Mediterranean areas. Under drought stress, many plants react by inducing a different series of responses at both physiological and molecular levels, allowing them to survive for a variable period of time. Therefore, in order to understand the response of roots to drought conditions, the genotypes peach × almond 'Garnem' [P. amygdalus Batsch × P. persica (L.) Batsch] and their progeny, the hybrid 'P.2175' × 'Garnem'-3 and OP-'P.2175' (P. cerasifera Ehrh.) were subjected to a period of water deficit. Drought conditions with a subsequent re-watering period were tested for potted plants for one month. Stomatal conductance and leaf water potential were measured to monitor the plant physiological responses. Significant differences among the drought stress and drought stress recovery treatments and among the genotypes were observed. In addition, four genes related to the ABA biosynthesis pathway were studied for their expression by RT-qPCR: an AN20/AN1 zinc finger protein (ppa012373m); a bZIP transcription factor (ppa013046m); a dehydrin (ppa005514m) and a LEA protein (ppa008651m). Their expression profiles correlated with our physiological results of drought response, being higher in roots than in phloem tissue. In general, the expression of the four studied genes was higher after 15 days under drought conditions. Under drought and recovery conditions, the zinc finger and bZIP transcription factors showed significant differences in their relative expression levels from LEA and dehydrin. These results suggest the role of LEA and dehydrin in the regulatory response to drought stress in Prunus genotypes. Therefore, the dehydrin and the protein LEA might be potential biomarkers to select rootstocks for tolerance to drought conditions.