Expression of OePIP2.1 aquaporin gene and water relations of Olea europaea twigs during drought stress and recovery

To investigate the effects of drought and recovery on the transcript level of OePIP2.1 (a PIP2 aquaporin gene) in twigs, 2-year-old olive trees were subjected to a drought/rewatering treatment (the irrigation was suspended for a period of 4 weeks and restored for the following 4 weeks). Twig water potential, twig hydraulic resistance and incidence of embolisation in the twig were measured in parallel with gene expression under both drought stress and the following recovery. During drought, a decrease in twig water potential, an increase in twig hydraulic resistance and an increase in the extent of xylem vessel embolisation was observed in parallel with a decrease of aquaporin gene expression. Opposite trends were recorded during rewetting. A speculation on a possible contribution of OePIP2.1 aquaporin to modulate shoot embolism during drought and recovery is proposed.