Expression of Vitis amurensis NAC26 in Arabidopsis enhances drought tolerance by modulating jasmonic acid synthesis

The growth and fruit quality of grapevine are widely affected by abnormal climatic conditions such as water deficit. But how grapevine responds to drought stress is still largely unknown. Here we found that VaNAC26, a member of NAC transcription factor family, was up-regulated dramatically during cold, drought and salinity treatments in Vitis amurensis, a cold and drought-hardiness wild Vitis species. Ectopic overexpression of VaNAC26 enhanced the drought and salt tolerances in transgenic Arabidopsis. Higher activities of antioxidant enzymes and the lower concentration of H2O2 and O2- were found in VaNAC26-OE lines than in wild type plants under drought stress. These results indicate that the reactive oxygen species (ROS) scavenging was enhanced by VaNAC26 in transgenic lines. Microarray based transcriptome analysis reveals that genes related to jasmonic acid (JA) synthesis and signaling were up-regulated in VaNAC26-OE lines under both normal and drought conditions. VaNAC26 showed a specific binding ability on NACRS motif, which was broadly existent in the promoter regions of up-regulated genes in transgenic lines. Endogenous JA content was found increased obviously in VaNAC26-OE-2/3 lines. Our data suggests that VaNAC26 responds to abiotic stresses and may enhance the drought tolerance by transcriptional regulation of JA synthesis in Arabidopsis. Leaves from wild-type and three transgenic lines were collected before and after 5 d of drought stress. An equal amount of leaves from three independent transgenic lines that were harvested in same day was pooled as OE lines for RNA isolation. Four samples were collected, which including WT 0d, OE 0d, WT 5d and OE 5d and each sample were represented by two replicates.