Enzymatic activity and functional analysis under multiple abiotic stress conditions of a dehydroascorbate reductase gene derived from Liriodendron Chinense

Dehydrogenase ascorbic reductase (DHAR) is a critical enzyme involved in resistance to environmental stress. However, few DHAR genes have been identified in woody plants. Liriodendron chinense is a relict tree species of Magnoliaceae. Due to its outstanding ornamental features and fine wood properties, L. chinense is becoming increasingly applied in both timber production and landscaping. A broad ability to adapt is the initial premise of extensive planting of trees; as a result, discovery and functional validation of resistance genes are extremely important. In this study, a putative DHAR gene was isolated from L. chinense. The full-length coding sequence of the LcDHAR gene was cloned and expressed in Escherichia coli. The enzyme was then isolated and purified to investigate its activity and obtain its Michaelis constant. The results showed that the LcDHAR gene encodes a 216-aa protein that contains a complete DHAR domain. Subcellular localization assay revealed LcDHAR a cytoplasmic protein. We further calculated K-m(GSH) and K-m(DHA) values of 1.04 mM and 0.81 mM, respectively, for LcDHAR. Moreover, overexpression of the LcDHAR gene in Arabidopsis thaliana led to a higher content of AsA as well as enhanced salt and drought stress resistance. In addition, the transgenic plants produced leaves at an earlier time and the root length was significantly longer than that of col-0 wild-type line under gradient salt and drought stresses. Taken together, the results of this study reveal that LcDHAR might play a protective role in response to salt and drought stresses and provide a partial framework for LcDHAR gene regulation of DHA and AsA contents in Liriodendron.