Proteomic Analysis of Responses to Drought Stress in Sunflower (Helianthus annuus) Leaves by 2DE Gel Electrophoresis and Mass Spectrometry

By using a differential proteomic approach, responses to drought stress in sunflower have been studied. Two sunflower genotypes, showing different levels of tolerance to drought have been utilized. Following TCA-acetone protein extraction, the 2-DE leaf protein profile of well watered and drought stressed plants have been compared. Coomassie staining of the gels allowed visualization of around 350 well resolved spots within the 5-8 pH and 10–100 kDa ranges. Image analysis revealed the presence of both, qualitative and quantitative changes between genotypes and treatments. Differential spots were subjected to trypsin digestion and peptides were analyzed by MALDI-TOF mass spectrometry. After database search using peptide mass fingerprinting, 2 genotype-dependent and 23 (susceptible genotype) and 5 (tolerant genotype) stress-responsive protein spots were identified. The two proteins spots differentiating sunflower genotypes corresponded to phosphoglycerate kinase and glyceraldehyde-3-phosphate dehydrogenase. In response to drought conditions a general decrease in protein spots corresponding to enzymes of the photosynthesis and carbohydrate metabolism was observed in the more susceptible genotype, suggesting inhibition of the energetic metabolism. Such changes have not been observed in the tolerant genotype, indicating a normal metabolism under drought stress.