Overexpression of genes encoding enzymes involved in trehalose synthesis from Caragana korshinskii enhances drought tolerance of transgenic plants

Abstract

Trehalose, which plays important roles in resistance to abiotic stresses and preservation of biological activity in plants, is synthesized by two key enzymes, trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP). Therefore, the expressions of the TPS and TPP genes directly affect trehalose synthesis and stress resistance of plants. In this study, CkTPS and CkTPP from Caragana korshinskii were identified, and the role of trehalose synthesis in the adaptation of this desert plant to adverse conditions was investigated. Higher CkTPS and CkTPP expressions were observed in the roots, whereas expressions were much lower in leaves and stems, and their expressions were upregulated under drought stress. Histochemical analyses showed that β-glucuronidase expression driven by the CkTPS and CkTPP promoters was strongly induced by abiotic stresses and phytohormones, such as abscisic acid, gibberellin, methyl jasmonate, and mannitol, which suggests that trehalose synthesis may be regulated by various signaling pathways. To determine the functional mechanism underlying the role of trehalose synthesis in regulating drought response in plants, CkTPS and CkTPP were introduced into Arabidopsis. Compared to wild-type (WT) plants, these transgenic plants showed higher germination rate, survival, less damage, better shoot growth, and longer roots under drought stress. Moreover, transgenic plants had a significantly higher content of proline, chlorophyll, trehalose, and activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and lower malondialdehyde (MDA) content than WT controls. Double-transgenic plants carrying CkTPS and CkTPP showed better growth and stronger drought tolerance than either single transgenic plant line. These results provide a theoretical and experimental basis for further understanding the function and regulatory mechanism of CkTPS and CkTPP, as well as the possibility of their application for improving drought tolerance in crops through genetic engineering.