Abstract
The MYB family plays a vital role in regulating plant stress resistance. However, the MYB protein in blue honeysuckle remains largely unexplored. In this study, the LcMYB90 gene from blue honeysuckle 'Lanjingling' was stably transformed into tobacco and transiently transformed into blue honeysuckle to characterize its function. Subcellular localization analysis revealed that the LcMYB90 protein is localized in the nucleus. Transgenic plants overexpressing LcMYB90 exhibited enhanced growth performance and higher survival rates under drought and salt stress conditions. These plants also showed increased levels of proline and chlorophyll, along with elevated activities of catalase, peroxidase, and superoxide dismutase. Conversely, malondialdehyde content and relative conductivity were lower, indicating that LcMYB90 enhances tolerance to drought and salt stress. Under salt treatment, genes induced by osmotic stress, such as NHX1 (Na(+)/H(+) antiporters 1) and SOS1 (salt overly sensitive 1), as well as antioxidant defense system genes like SOD (superoxide dismutase) and CAT1 (catalase 1), were more highly induced in overexpression lines compared to the wild type, supporting the hypothesis that LcMYB90 promotes salt tolerance by enhancing osmotic stress resistance and antioxidant capacity. Simultaneously, the transcription levels of genes involved in the abscisic acid pathway, including NCED1/2 (9-cis-epoxycarotenoid dioxygenase 1/2, PYL4/8 (pyrabactin resistance-Like 4/8), and CBL1 (Calcineurin B-like protein 1), were increased under drought stress conditions in the overexpression lines. These results suggest that LcMYB90 maintains cellular homeostasis by promoting the expression of stress-related genes and regulating osmotic and oxidative substances, thereby improving tolerance to drought and salt stress.