Expression analysis and physiological response of sunTIP7 aquaporin gene to different water regimes in sunflower

The response of a plant to drought stress is positively related to physiological traits and gene expression. Various recent studies suggest that membrane channel proteins, named aquaporin (AQPs), by affecting stomatal conductance behavior could be involved in plant responses to stress conditions. The sunTIP7 gene is a member of AQPs protein that is included in different environmental stress such as drought stress. In this study in order to investigate the sunTIP7 gene expression and its relation with relative water content (RWC), stomatal conductance, shoot fresh and dry weight, root area, chlorophyll index (SPAD) and electrolyte leakage (EL), six selected sunflower (Helianthus annuus L.) inbred lines were planted in a greenhouse under normal irrigation and water deficit conditions. The water deficit treatments were applied during 4th leaflet to flowering stage. Drought conditions reduced crop growth and physiological traits. The highest stomatal conductance was found in the C138 line under both conditions. Sunflower lines had different fold change expression of sunTIP7 gene under drought stress. The expression of the sunTIP7 gene was the lowest in C138, and this downregulation may explain its highest stomatal conductance. However, there was not any clear relationship between physiological traits and expression of sunTIP7 gene in all six sunflower inbred lines. These results suggest that drought tolerance in sunflower is a complex trait and there is no simple molecular explanation for drought tolerance in sunflower lines.