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Figure 1.  Schematic structures of MBD proteins; CsMBD1-16 from the tea plant and AtMBD1-13 from Arabidopsis. The conserved MBD domains are indicated with green rectangles. The length of the box represents the length of the domain. Different coloured rectangles represent different protein domains.

Figure 2.  Alignment of MBD domains of the AtMBD1-13 from Arabidopsis, CsMBD1-16 from the tea plant and MeCP2 proteins from humans. The secondary structure for amino acid conservation is displayed at the top: four β-sheet strands (β1–4), one α-helix, and two loop regions (L1–2). Five asterisks indicate the positions of residues that may be crucial for the binding of MBD proteins to methylated DNA.

Figure 3.  Phylogenetic tree of MBD proteins in tea plants (16), poplar (15), rice (14) and Arabidopsis (13). The unrooted tree was created using MEGA7.0 by the neighbour-joining method. The bootstrap value = 1,000.

Figure 4.  Duplication analysis of MBD genes in tea plants and Arabidopsis. (a) Synteny analysis of 16 CsMBD genes in tea plants. (b) Synteny analysis of MBD genes between tea plants and Arabidopsis. Gray lines in the background indicate the collinear blocks within the tea plant and other plant genomes, while the red lines highlight the syntenic MBD gene pairs.

Figure 5.  Analysis of cis-acting elements in the promoter region of 16 CsMBD genes. (a) The number of different cis-acting regulatory elements in the promoter region. (b) The histogram of cis-acting elements in four categories.

Figure 6.  Tissue-specific expression profile clustering of 15 CsMBDs. The colour scale indicates log₂ signal values (right); blue and red colours indicate low and high levels of transcript abundance, respectively. The different organs are noted on the right. A cluster dendrogram is shown above.

Figure 7.  Expression profiles of 15 CsMBD genes under biotic stress treatments in tea plants. The different colours indicate different plant diseases and insect pests. The error bars indicate the standard error of the mean (SEM) from three biological replicates. * Significant differences (p < 0.05), ** highly significant differences (p < 0.01).

Figure 8.  Relative expression of 15 CsMBD genes under abiotic stresses in tea plants. (a) Cold acclimation; (b) drought stress conditions. The y-axis represents the transcript abundance, and the x-axis represents the stress treatments (days or date). The error bars indicate the standard error of the mean (SEM) from three independent biological replicates. * Significant differences (p < 0.05), ** highly significant differences (p < 0.01).

Figure 9.  Expression patterns of 15 CsMBD genes during growth and development in tea plants. Including seed germination, floral development and different dormancy stages in tea plants; p < 0.05 was considered significant (*) and p < 0.01 was considered highly significant (**). The colour scale indicates the log₂ signal values shown on the right. Red and blue indicate high and low levels of expression, respectively. A cluster dendrogram is shown on the left of the graph.