BpMYB06 Acts as a Positive Regulatory Factor in Saline–alkaline Stress Resistance by Binding to Two Novel Elements

Abstract Saline–alkaline salinity is recognized as one of the most severe abiotic stress factors, limiting plant growth and resulting in significant yield losses. MYB transcription factors (TFs) are crucial for plant tolerance to abiotic stress. However, the roles and regulatory mechanism of MYB TFs underlying saline–alkaline stress tolerance have not yet been investigated in Betula platyphylla. In this report, BpMYB06, an R2R3-MYB TF, is induced in response to saline–alkaline stress in B. platyphylla. This protein functions as a nuclear-localized transcriptional activator. Both gain- and loss-of-function analyses indicate that the transcript level of BpMYB06 is positively correlated with saline–alkaline stress tolerance, primarily through the enhancement of reactive oxygen species scavenging and the regulation of osmotic and ionic balance. Additionally, BpMYB06 is implicated in the control of stomatal aperture. Quantitative real-time PCR results show that BpMYB06 regulates the expression of genes associated with stress tolerance. Furthermore, TF-centered Y1H and chromatin immunoprecipitation assays reveal that BpMYB06 binds to two novel core sequences ([A/C]CGG and TAG[C/A]), thereby inducing the expression of stress-related genes. Our findings provide new insights into the role of BpMYB06 in B. platyphylla under soda saline–alkaline stress and suggest that it could serve as a potential target gene for developing saline–alkaline stress-tolerant B. platyphylla plants.