Climate evolution will tends to an increase of frequency and severity of droughts. These changes may alter the distribution and potential survival of plant species. Drought treatment observed on trees induces diverse responses in function of ecological strategies which depend on genotype x environment interaction. Earlier modifications of ecophysiological traits (stomata closure, photosynthesis decrease, and hydraulic tension increase) in response to drought stress can be qualified as isohydric as opposed to anisohydric behaviour. Then our objective was to test if these contrasted phenotypes had a specific transcriptional regulation. Production and hydraulic traits were monitored during severe stress on six Populus nigra genotypes in order to bring out ecophysiological traits which are genotypespecific and to characterise droughtresponse strategies. Multivariate analysis on ecophysiological traits allowed us to choose the most indicative ones of hydraulic and physiological plant status and to define iso- or anisohydric genotypes. Total RNA sequencing was performed by RNAseq, on new leaves formed during stress, sampled at the maximum drought stress intensity indicated by predawn leaf water potential. A statistical analysis of transcripts expression levels was carried out to clean out the data and to reveal trends. Afterwards, these informations were analysed along with genes groups involved in leaf blade water regulation to estimate relationships between expression level and ecophysiological responses.