<i>VcTT2</i> enhances drought tolerance in blueberry by regulating ROS scavenging

Blueberries are highly valued for their nutritional richness and distinctive flavor. However, they are susceptible to drought stress, which adversely affects growth, yield, and fruit quality. Therefore, improving drought tolerance in blueberries is crucial for industrial development. In this study, VcTT2 (also named VcMYBPA2.1), a gene encoding a TT2-type MYB transcription factor, was identified, and its expression was found to be induced by drought, salt, and low-temperature stresses. Overexpression of VcTT2 in blueberry calli enhanced drought tolerance by increasing the activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) enzymes, promoting proline accumulation, and reducing malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels. Furthermore, overexpression of VcTT2 improved drought tolerance in blueberry seedlings, whereas suppressing this gene resulted in decreased drought tolerance. Overexpression of VcTT2 significantly upregulated the expression of genes related to reactive oxygen species (ROS) scavenging under drought stress, including VcSOD1, VcSOD2, VcPOD1, VcPOD2, VcAPX1, and VcAPX2. Collectively, under drought stress, VcTT2 overexpression enhanced the activities of antioxidant enzymes APX, SOD, and POD by promoting the expression of downstream antioxidant enzyme genes, thereby scavenging the over-accumulated ROS and improving the drought tolerance of blueberries. These findings reveal the function and mechanism of VcTT2 in enhancing drought tolerance in blueberry by regulating ROS levels, providing a theoretical basis and genetic resources for drought-tolerant germplasm improvement in blueberry.