Cloning and expression analysis of MsVDE in escaped alfalfa in Yunnan, China

The xanthophyll cycle of thermal dissipation is one of the photoprotective pathways for plants in response to environmental stresses. The VDE gene is crucial in the cyclic de-epoxidation of xanthophyll. In this study, the VDE gene of alfalfa (Medicago sativa; MsVDE) that had escaped in the Yunnan area of China was cloned for the first time using the RACE technique. Real-time fluorescence quantitative technology was also used to analyze characteristics of MsVDE expression under drought and heat stresses. Full-length MsVDE cDNA was successfully cloned from escaped alfalfa. The 1608 bp coding sequence specified 535 amino acids. Homologous sequence alignment showed that the MsVDE sequence of escaped alfalfa encoded three characteristic VDE gene family domains: The N-terminal cysteine-rich region, lipid carrier protein region, and C-terminal glutamate-rich region. Sequence alignment and phylogenetic analysis showed that MsVDE had the closest relationship with thistle alfalfa (M. truncatula). MsVDE expression was up-regulated 2.13 times and 1.97 times under drought and stresses compared with normal conditions on day 4 and day 8, respectively. MsVDE expression in leaves sprayed with dithiothreitol solution was down-regulated by 55% on average. The results show that the MsVDE gene of alfalfa that has escaped in the Yunnan area could play an important role in photoprotection and regulation of the xanthophyll cycle under drought and heat stresses.