Physiological Changes and Expression of SOD and P5CS Genes in Response to Water Deficit in Sugarcane

Drought stress is one of the major environmental stresses affecting growth and productivity of sugarcane in many areas of tropical and subtropical India. Resistance to water deficit in plants can occur through proline accumulation and higher expression of antioxidant enzymes. The differential expression patterns of drought-responsive genes in different plant tissues at different growth stages could provide an opportunity to characterize the traits associated with yield advantage under drought and to understand the physiological and molecular mechanisms that confer increased drought tolerance. Present study was aimed to examine the effect of short term water deficit on physiological attributes and expression of superoxide dismutase (SOD), and P5CS (pyrroline-5-carboxylate synthetase) genes using two sugarcane varieties, CoLk 94184 (an early maturing) and BO 91 (a mid late maturing). Single bud setts of two varieties of sugarcane were planted in earthen pots filled with soil in the month of February, 2013. After about 60 days of planting, water deficit was created by withholding water supply for 24, 48, and 72 h along with control and recovery treatment. Results obtained indicated increased proline content in leaf tissues with an increase in duration of water deficit; highest increase was observed at 72 h of water deficit conditions. Early maturing variety, CoLk 94184 showed higher accumulation of proline content with severe wilting as compared to mid late maturing variety BO 91. RWC, chlorophyll and carotenoids contents and SPAD reading decreased with water deficit level, while, recovery treatment showed increase in these attributes in both the varieties. Specific activity of SOD and peroxidase enzymes increased due to water deficit conditions. Quantitative expression of SOD and P5CS genes increased only up to 48 h of water deficit treatment and at 72 h treatment their expression was low. After recovery treatment, gene expression increased in both the varieties. Higher expression of SOD and P5CS genes up to certain level of water deficit (48 h), proline content and activity of antioxidant enzymes (SOD and peroxidase) may help in tolerance to water deficit condition.