Abstract
Tonoplast aquaporins (intrinsic proteins, TIPs) have been indicated to play important roles in plant tolerance to water deficit and salinity. However, the functions of wheat TIPs in response to the stresses are largely unknown. In this study, we observed that transgenic plants overexpressing wheat TaTIP4;1 in Arabidopsis and rice displayed clearly enhanced seed germination and seedling growth under drought, salt and osmotic stress. Compared with wild type plants, Arabidopsis and rice overexpression lines had heightened water contents, reduced leaf water loss, lowered levels of Na+, Na+/K+, H2O2 and malondialdehyde, and improved activities of catalase and/or superoxide dismutase, and increased accumulation of proline under drought, salinity and/or osmotic stresses. Moreover, the expression levels of multiple drought responsive genes clearly elevated upon water dehydration, and the transcription of some salt responsive genes was markedly induced by NaCl treatment in the overexpression lines. Also, the yeast cells containing TaTIP4;1 showed increased tolerance to NaCl and mannitol, and mutation in one of three serines of TaTIP4;1 caused decreased tolerance to the two stresses. These results suggest that TaTIP4;1 serves as an essential positive regulator of seed germination and seedling growth under drought, salt and/or osmotic stress through impacting water relations, ROS balance, the accumulation of Na+ and proline, and stimulating the expression of dozens of stress responsive genes in Arabidopsis and rice. Phosphorylation may modulate the activity of TaTIP4;1.
Highlights
Drought and high salinity are two crucial environmental stresses that greatly limit plant growth, development and crop productivity worldwide
Water deficit can lead to the enhancements in the activities of different antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX)
tonoplast intrinsic proteins (TIPs) have been addressed to fulfill functions in plant adaption to various abiotic stresses [23]
Summary
Drought and high salinity are two crucial environmental stresses that greatly limit plant growth, development and crop productivity worldwide. Drought reduces cellular water contents, and salinity disturbs ion balance. Both stressors can result in hyperosmotic stress. Plants have developed complicated regulatory mechanisms to withstand these environmental challenges and the resultant secondary stresses, including the perception and transduction of stress signals, the activation of stress responsive transcription factors, followed by the induction of the expression of a large number of functional genes [3–6]. Drought signals are sensed and relayed downstream to promote the increase in water uptake from the soil. Dehydration stress stimulates the biosynthesis of hormone abscisic acid (ABA) to induce stomatal closure, preventing water loss. Water deficit can lead to the enhancements in the activities of different antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX)
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