The cold-stress responsive gene involved in low-temperature tolerance in Xinjiang wild walnut.

Background: Low-temperatures have the potential to be a serious problem for plants and can negatively affect the normal growth and development of walnuts. DREB1/CBF (Dehydration Responsive Element Binding Protein 1/C-repeat Binding Factor), one of the most direct transcription factors in response to low-temperature stress, may improve the resistance of plants to low-temperatures by regulating their functional genes. However, few studies have been conducted in walnut. The Xinjiang wild walnut is a rare wild plant found in China, with a large number of excellent trait genes, and is hardier than cultivated walnuts in Xinjiang.

Methods: In this work, we identified all of the DREB1 members from the walnut genome and analyzed their expression levels in different tissues and during low-temperature stress on the Xinjiang wild walnut. The gene of the Xinjiang wild walnut was cloned and transformed into for functional verification.

Results: There were five DREB1 transcription factors in the walnut genome. Among them, the relative expression level of the gene was significantly higher than other members in the different tissues (root, stem, leaf) and was immediately un-regulated under low-temperature stress. The overexpression of the gene increased the survival rates of transgenic lines, mainly through maintaining the stability of cell membrane, decreasing the electrical conductivity and increasing the activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Additionally, the expression levels of cold-inducible genes like , , , and , were significantly increased. These results showed that the gene may play an important role in the response to cold stress of the Xinjiang wild walnut. This study contributes to our understanding of the molecular mechanism of the Xinjiang wild walnut's response to low-temperature stress and will be beneficial for developing walnut cultivars with improved cold resistance.