Intracellular trehalose modulates oxidative responses and dehydrin gene expression in Arabidopsis thaliana (L.) Heynh during dehydration

Trehalose, a naturally occurring non-reducing sugar although observed in organisms such as bacteria, yeasts, and invertebrates, its abundance is very low or undetectable in many angiosperm plants. However, there were noticeable levels of trehalose with increased accumulation during dehydration and desiccation in resurrection plants such as Selaginella lepidophylla (Hook. & Grev.) Spring and Myrothamnus flabellifolia Welw. specifying its importance in affording protection to cells from stress-induced damage. Recent evidences suggest the active role of trehalose in plant growth and abiotic stress tolerance. In the current study, callus tissues from leaves and seeds, seedlings, and adult plants representing different tissues at distinct stages of growth of A.thaliana plants were used to increase the cellular concentration of trehalose either by treating the tissues with different concentrations of trehalose or by treating them with validamycin A (trehalase inhibitor) under non-stress conditions to study its role in modulation of oxidative stress responses and expression of dehydrins. Accumulation of trehalose in callus tissues generated from seeds and leaves by validamycin A treatment resulted in induction in the expression of multiple dehydrins particularly at 50, 100, and 200 µM concentrations. Although the induction in the expression of dehydrins was higher in the seed derived callus than leaf callus in validamycin A-treated samples, accumulation of trehalose has shown induced expression of dehydrins in both the callus tissues under unstressed conditions indicating the role of trehalose in stress-signalling. The gradual increase in the trehalose content observed in the seedlings of A. thaliana treated with different concentrations of trehalose or with different concentrations of validamycin A correlated well with the increased expression of RAB18, LEA64, ERD10, XERO2, and COR47 dehydrin genes and increased antioxidant activity. The leaves of adult A. thaliana plants treated with 50 mM trehalose under control (80–90% RWC), drought with high RWC (DH 50–60% RWC) and drought with low RWC (10–30% RWC) showed trehalose mediated modulation in oxidative stress responses and dehydrin gene expression. Although remarkable changes in RWC and EC were not observed in leaves of DH and DL plants treated with 50 mM trehalose, the decrease in ROS levels in trehalose-treated leaves correlating with higher activityf of SOD, CAT, and APX antioxidant enzymes and increased expression of dehydrin genes strongly indicates trehalose as a modulator for oxidative responses and dehydrin gene expression. Cumulatively our results with trehalose under non-stress control conditions and dehydration stress conditions suggests that trehalose mimics the stress responses in plants thereby modulating the expression of stress-responsive dehydrin genes and antioxidant enzymes equipping the plants with early defense.