Effects of melatonin on growth and biochemical properties of Vitis vinifera suspension cells under low temperature stress

Abstract [Objective] The study aims to analyze the effects of melatonin (MT) on the growth, biochemical characteristics, and expression of cold-responsive genes in grapevine (Vitis vinifera L.) suspension cells under low temperature stress, to screen the appropriate MT concentrations and to investigate the mechanism of MT in enhancing cold tolerance of grapevine. [Methods] Using ‘Pinot Noir’ grapevine suspension cells as test materials, we investigated the effects of different concentrations of MT [0 (CK), 50 (T1), 100 (T2), 200 (T3), 300 μmol/L (T4)] on the growth of the suspension cells, the content of malondialdehyde (MDA), the content of proline (Pro), and the antioxidant enzyme activities, and changes in gene expression related to cold response to T2 treatment, under low temperature (4 ℃) stress, [Results] (1) Under low temperature stress, the dry weight of cells in each MT treatment showed a trend of first increase then decrease, which was finally stable or decreased, and was higher than CK at the end of treatment. (2) MDA and Pro contents of each treatment were firstly increased and then decreased with the time of treatment, which reached the peak at 24 h or 48 h. MDA content of each MT treatment was lower than that of CK, while the Pro content was higher than that of CK, with T2 treatment being the lowest or the highest. (3) The antioxidant enzyme activities of each MT treatment were higher than that of CK, with T2 treatment being the highest. With the prolongation of time, the activities of POD and CAT of each treatment firstly rose and then fell, while the activities of SOD and APX firstly fell and then rose, which reached the highest at 24 h or 6 h, respectively. (4) The relative expression of cold-responsive genes (VvCBFs, VvICE1, VvRD29B, and VvKIN-2) in T2-treated suspension cells were up-regulated compared with CK. [Conclusion] Under low temperature stress, the appropriate concentration (100 μmol/L) of MT increases the expression of antioxidant enzymes and cold-response genes, increases Pro content, decreases MDA content, and enhances low temperature tolerance of grapevine suspension cells.