Differential physiological responses of three Sesame genotypes to drought stress and the expression of antioxidant genes

Abstract

This study was conducted to determine the physiological responses and the expression of major antioxidant genes (Cu/Zn-SOD, CAT, and APX) to drought stress in three sesame (Sesamum indicum L.) genotypes. Drought conditions were imposed at three levels: D1 (100%), D2 (50%), and D3 (25%) of field capacity on three major Iraqi genotypes of sesame, namely Wadaa, Sumer, and Local. The physiological results indicated that variety Wadaa was characterized by the highest relative water content (82%). The expression of Cu/Zn- SOD gene was influenced by drought in Wadaa variety and recorded the lowest gene expression compared to non-stress plants at 50% of field capacity. Gradual increase of expression was recorded in Sumer and Local varieties to reach 43.63 and 50.98-fold over, respectively of the normal expression. The expression of CAT gene was up-regulated in both Wadaa and Sumer for treatments D2 and D3, and up-expression for treatment D2 with the Local variety while down-regulated from normalized expression for D3 treatment (1.56-fold). The expression levels of APX gene increased in Wadaa variety for the treatment D2 and decreased for the treatment D3 by 83.33-fold. While its expression up-regulated for the treatments D2 and D3 in Sumer variety as well as in treatment D2 in the Local variety. Severe drought at 25% of field capacity caused down-regulated in APX in Local variety and scored 1.26-fold than non-stress plants.