Genome-wide investigation of methyl-CpG-binding domain genes in Brassica napus L. and functional characterization of BnaC09.MBD7 and BnaA10.MBD7 in modulating osmotic stress tolerance.

UNLABELLED: The gigabytes of eukaryotic genomes are indexed by biochemical modifications including methylation and highly compressed and stacked in the nuclei. Thus, organized access and expression of the genetic codes hidden in the highly compacted genomes is critical. The methyl-CpG-binding domain (MBD) proteins can specifically recognize and bind to the methylated CpG sites and regulate gene expression. To date, few MBD genes have been functionally characterized in plants and their regulatory mechanisms remain unclear. Brassica napus is an important crop sensitive to osmotic stress. Here, a total of 38 putative MBD-domain proteins were identified in Brassica napus and their potential roles in abiotic stress were investigated. BnaC09.MBD7 (BnaC09G0432500ZS) and BnaA10.MBD7 (BnaA10G0153000ZS) are a pair of closely related paralogs with similar expression patterns. Both the BnaC09.MBD7 and BnaA10.MBD7 showed nuclear localization. Heterologous expression of either BnaC09.MBD7 or BnaA10.MBD7 in Arabidopsis thaliana conferred tolerance to drought and salt stresses. However, the transgenic plants over-expressing BnaC09.MBD7 or BnaA10.MBD7 showed largely non-overlapped transcriptomes, suggesting they might act independently to reinforce the stress tolerance. Our results functionally characterized BnaC09.MBD7 and BnaA10.MBD7 of Brassica napus in response to osmotic stress and provided insights into the regulatory mechanisms BnaMBD genes. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at https://doi.org/10.1007/s12298-026-01805-4.