The impacts of allopolyploidization on Methyl-CpG-Binding Domain (MBD) gene family in Brassica napus

Genome-wide identification of MBD gene family members in Eleutherococcus senticosus with their expression motifs under drought stress and DNA demethylation

BACKGROUND

Methyl-binding domain (MBD) is a class of methyl-CpG-binding domain proteins that affects the regulation of gene expression through epigenetic modifications. MBD genes are not only inseparable from DNA methylation but have also been identified and validated in various plants. Although MBD is involved in a group of physiological processes and stress regulation in these plants, MBD genes in Eleutherococcus senticosus remain largely unknown.

RESULTS

Twenty EsMBD genes were identified in E. senticosus. Among the 24 chromosomes of E. senticosus, EsMBD genes were unevenly distributed on 12 chromosomes, and only one tandem repeat gene existed. Collinearity analysis showed that the fragment duplication was the main motif for EsMBD gene expansion. As the species of Araliaceae evolved, MBD genes also evolved and gradually exhibited different functional differentiation. Furthermore, cis-acting element analysis showed that there were numerous cis-acting elements in the EsMBD promoter region, among which light response elements and anaerobic induction elements were dominant. The expression motif analysis revealed that 60% of the EsMBDs were up-regulated in the 30% water content group.

CONCLUSIONS

By comparing the transcriptome data of different saponin contents of E. senticosus and integrating them with the outcomes of molecular docking analysis, we hypothesized that EsMBD2 and EsMBD5 jointly affect the secondary metabolic processes of E. senticosus saponins by binding to methylated CpG under conditions of drought stress. The results of this study laid the foundation for subsequent research on the E. senticosus and MBD genes.

Genome-Wide Characterization of the Methyl CpG Binding Domain-Containing Proteins in Watermelon and Functional Analysis of Their Roles in Disease Resistance Through Ectopic Overexpression in Arabidopsis thaliana

Methyl-CPG-Binding Domain (MBD) proteins play important roles in plant growth, development, and stress responses. The present study characterized the MBD families in watermelon and other cucurbit plants regarding the gene numbers and structures, phylogenetic and syntenic relationships, evolution events, and conserved domain organization of the MBD proteins. The watermelon ClMBD proteins were found to be localized in nucleus, and ClMBD2 and ClMBD3 interacted with ClIDM2 and ClIDM3. ClMBD2 bound to DNA harboring methylated CG sites but not to DNA with methylated CHG and CHH sites in vitro. The ClMBD genes exhibited distinct expression patterns in watermelon plants after SA and MeJA treatment and after infection by fungal pathogens Fusarium oxysporum f.sp. niveum and Didymella bryoniae. Overexpression of ClMBD2, ClMBD3, or ClMBD5 in Arabidopsis resulted in attenuated resistance against Botrytis cinerea, accompanied by down-regulated expression of AtPDF1.2 and increased accumulation of H2O2 upon B. cinerea infection. Overexpression of ClMBD1 and ClMBD2 led to down-regulated expression of AtPR1 and decreased resistance while overexpression of ClMBD5 resulted in up-regulated expression of AtPR1 and increased resistance against Pseudomonas syringae pv. tomato DC3000. Transcriptome analysis revealed that overexpression of ClMBD2 in Arabidopsis up-regulated the expression of a small set of genes that negatively regulate Arabidopsis immunity. These data suggest the importance of some ClMBD genes in plant immunity and provide the possibility to improve plant immunity through modification of specific ClMBD genes.