Genome-Wide Identification and Expression Profiling Reveal the Diverse Role of Methyl-CpG-Binding Domain Proteins in the Tea Plant Camellia sinensis

Methyl-CpG-binding domain (MBD) proteins are important DNA methylation readers that recognise methylated CpG sites and recruit histone deacetylase (HDAC) complexes and chromatin remodelling factors, leading to chromatin compaction, gene transcription, and genome integrity. Currently, MBD genes have only been identified in a few plant species and their structure and function in tea plants (Camellia sinensis) are unknown. In this study, 16 C. sinensis MBD genes (CsMBD) were identified on a genome-wide level and classified into eight classes. The CsMBD genes were mapped on nine chromosomes in tea plants, and nine pairs of CsMBD genes existed. Based on conserved domain analysis, all of the identified CsMBD proteins contained at least one MBD domain. Expression analyses showed that CsMBD genes were expressed in tissue- and organ-specific patterns. We investigated the expression patterns of CsMBD genes in response to abiotic and biotic stresses and during different plant growth and development stages. Multiple pthytohormone and stress-related cis-acting was evaluated in their promoter region, such as GGTCA, TGACG, ABRE and LTR. Specific CsMBD genes were associated with environmental stresses and developmental stages, with little overlap. Overall, our findings reveal the diverse roles of CsMBD genes under different stress and developmental conditions, highlighting candidate genes for further functional studies on tea plants.