Trehalose accumulation enhances drought tolerance by modulating photosynthesis and ROS-antioxidant balance in drought sensitive and tolerant rice cultivars

Trehalose being an integral part for plant growth, development and abiotic stress tolerance is accumulated in minute amounts in angiosperms with few exceptions from resurrection plants. In the current study, two rice cultivars differing in drought tolerance were used to analyse the role of trehalose in modulating photosynthesis and ROS-antioxidant balance leading to improvement in drought tolerance. Accumulation of trehalose in leaves of Vaisakh (drought-tolerant) and Aiswarya (drought-sensitive) rice cultivars was observed by spraying 50 mM trehalose and 100 mu M validamycin A (trehalase inhibitor) followed by vacuum infiltration. Compared to stress sensitive Aiswarya cultivar, higher trehalose levels were observed in leaves of Vaisakh not only under control conditions but also under drought conditions corresponding with increased root length. The increase in leaf trehalose by treatment with trehalose or validamycin A corresponded well with a decrease in electrolyte leakage in sensitive and tolerant plants. Decreased ROS levels were reflected as increase in antioxidant enzyme activity and their gene expression in leaves of both the cultivars treated with trehalose or Validamycin A under control and drought conditions signifying the importance of trehalose in modulating the ROS-antioxidant balance for cellular protection. Further, higher chlorophyll, higher photosynthetic activity and modulation in other gas exchange parameters upon treatment with trehalose or validamycin A strongly suggested the beneficial role of trehalose for stress tolerance. Trehalose accumulation helped the tolerant cultivar adjust towards drought by maintaining higher water status and alleviating the ROS toxicity by effective activation and increment in antioxidant enzyme activity along with enhanced photosynthesis.