DcDREB1A, a DREB-binding transcription factor from Daucus carota, enhances drought tolerance in transgenic Arabidopsis thaliana and modulates lignin levels by regulating lignin-biosynthesis-related genes

Carrot (Daucus carota L.) is an important root vegetable of Apiaceae, whose growth and production are negatively affected by abiotic stress. Dehydration-responsive element-binding protein (DREB) transcription factors usually play significant roles in the responses of plants to abiotic stress. However, knowledge on the functions of DREB transcription factors in carrots remains limited. In this study, the functional characterization of a DREB gene, DcDREB1A, cloned from carrot was reported. DcDREB1A was found to be a nuclear protein that can specifically bind to DRE element. Under drought treatment, DcDREB1A overexpression in transgenic plants resulted in increased superoxide dismutase (SOD) and peroxidase (POD) activities and decreased size of stomata apertures. Moreover, transgenic plants accumulated an increased amount of lignin and exhibited higher expression levels of lignin biosynthesis gene compared with wild-type plants. Overall, our findings revealed that DcDREB1A was involved in the regulation of plant tolerance to drought. DcDREB1A served as a positive regulator by regulating the activities of reactive oxygen species (ROS)-scavenging enzymes (SOD and POD) to maintain ROS homeostasis in cells, reducing stomata apertures and density, modulating lignin synthesis to control water loss, and inducing the expression of stress-responsive genes.