Integrative approach of the response of P. euphratica to drought and recovery: from genes to ecophysiology

International audience

anglais. Plantlets of Populus euphratica (from Ein Avdat natural park, Israel) were obtained by in vitro culture, ex vitro acclimated, transferred and acclimated to Nancy's greenhouse conditions. They were transplanted into 7.5 L-pot filled with peat-sand mix (50/50 V/V). A moderate, increasing drought stress was applied and controlled for 6 weeks through soil volumetric water content (SWC). A predetermined batch of plantlets (including control and stressed trees) was harvested at 4 stress intensities (10, 7.5, 5, 4% SWC) and after 10 days back to fully available water, in order to analyse transcriptome in leaves and roots, and proteome and other biochemical compounds in leaves (pigments, soluble carbohydrates). Growth (height, diameter, root elongation), water potential, leaf relative water content, net CO2 assimilation rate and stomatal conductance were measured on another batch of plants following the same drought time course and recovery. The degree of sensitivity to drought of the measured physiological parameters was established. The most sensitive to the less sensitive were stem diameter growth, height diameter, stomatal conductance, leaf relative water content, mid-day leaf water potential, photosynthesis, root elongation and predawn leaf water potential. An EST database with the P. euphratica ESTs including annotative attributes can be viewed at http://sputnik.btk.fi. In common with other P. euphratica microarray experiments, very few genes (68 in leaves and 39 in roots of the 7400 present on the array) were regulated by drought. In leaves, the number of regulated genes which increased with stress intensity returned to almost zero after re-irrigation. By contrast, the number of proteins in which abundance was modified decreased with stress intensity and remained important after re-irrigation. Moreover, while the fold change of most up-regulated genes increased with stress intensity, the relative abundance of most proteins was diminished with increasing stress intensity. Nature of regulated genes, at the level of the transcript or of the protein, are analysed and discussed in relation to ecophysiological responses.