Combining Proteomic Approach with Morpho-Physiological Changes to Assess the Effect of Drought Stress on Olive Plants at Young Stage of Development

Drought at early developmental stages severely limits olive (Olea europaea L.) production. Currently, “omics” approaches, such as proteomics, offer a unique opportunity to better elucidate plant responses to drought. Integrating this approach with morphological and physiological changes will enhance our understanding of the mechanisms underlying drought stress in this species. Herein, drought was imposed by total water depletion for 30 days and compared to well-watered plants. Results revealed that drought induced a decrement decrease in relative water content, reaching critical values below 40%, and triggered significant variations in morphological traits, including decrease in foliar biomass along with a drastic decrease in leaf area and leaf specific area in stressed olive plants. Furthermore, our physiological data indicate the inhibition of olive’s photosynthetic machinery under drought. Foliar-proteomic profiles of olive, performed using 2D gel electrophoresis and then liquid chromatography electrospray ionization-linear ion trap-tandem mass spectrometry (nanoLCESI-LIT-MS/MS), led to the identification of 20 leaf proteins of olive whose levels are altered in response to drought, particularly those related to the Calvin-Benson photosynthetic cycle (Rubisco, Rubisco activase), PS II stabilization (oxygen evolving protein (OEE1, OEE2), components of electron transport system (β subunits ATP synthase) and nitrogen metabolism (glutamine synthetase and bark storage protein). Despite all these changes, mineral status and especially foliar nitrogen levels remained stable, possibly due to the translocation of nitrogen from roots to leaves and the degradation of nitrogen-storing proteins like Rubisco and bark storage proteins.