Physiology and proteomics of drought stress acclimation in sunflower (Helianthus annuus L.).

An easy and manageable in vitro screening system for drought tolerance of sunflower seedlings based on MS media supplemented with polyethylene glycol 6000 was evaluated. Morphological and physiological parameters were compared between control (-0.05 MPa) and drought-stressed (-0.6 MPa) seedlings of Helianthus annuus L. cv. Peredovick. There was a significant growth deficit in drought-stressed plants compared to control plants in terms of hypocotyl length, and shoot and root fresh mass. Shoot growth was more restricted than root growth, resulting in an increased root/shoot ratio of drought-stressed plants. Accumulation of osmolytes such as inositol (65-fold), glucose (58-fold), proline (55-fold), fructose (11-fold) and sucrose (eightfold), in leaves of drought-stressed plants could be demonstrated by gas-liquid chromatography. Soluble protein patterns of leaves were analysed with two-dimensional gel electrophoresis (2D-PAGE) and MALDI-TOF mass spectrometry. A set of 46 protein spots allowed identification of 19 marker proteins. Quantitative changes in protein expression of drought-stressed versus control plants were detected. In leaves of drought-stressed sunflower seedlings six proteins were significantly up-regulated more than twofold: a putative caffeoyl-CoA 3-O-methyltransferase (4.5-fold), a fructokinase 3 (3.3-fold), a vegetative storage protein (2.5-fold), a glycine-rich RNA binding protein (2.2-fold), a CuZn-superoxide dismutase (2.1-fold) and an unknown low molecular weight protein (2.3-fold). These proteins represent general stress proteins induced under drought conditions or proteins contributing to basic carbon metabolism. The up-regulated proteins are interesting candidates for further physiological and molecular investigations regarding drought tolerance in sunflower.