Methyl-CpG-binding domain (MBD) proteins in plants are important trans-acting factors specifically recognizing methylated DNA. The MBD proteins can compact chromatins to repress transcription by recruiting chromatin-modifying complexes that contain histone deacetylase activities and chromatin remodeling factors, and play a crucial biological role in the growth and development in plants. Currently, very little is known regarding the structure and function of MBD genes in plants. In this study, we performed a genome-wide identification and expression profile analysis of maize MBD genes (ZmMBDs) from the latest version of the maize (B73) genome. By analyzing phylogenetic relationship of MBD gene families from Arabidopsis, rice, wheat, and maize, all 14 MBD proteins in maize were categorized into four subclasses. Furthermore, chromosome location and schematic structure revealed an unevenly distribution on chromosomes and structure features of MBD genes in maize, respectively. Eventually, EST expression data mining, microarray data clustering analysis, and semi-quantitative and quantitative expression profile analyses detected in seedling leaves and stems by heat, drought, and salt-stress treatments have demonstrated that these genes had temporal and spatial expression pattern and exhibited different expression levels under heat, drought, and salt-stress conditions, suggesting that functional diversification of the MBD gene family in maize. In addition, through electrophoretic mobility shift assay (EMSA) a representative MBD protein, ZmMBD11, exhibited in vitro DNA-binding activity, indicating that that the MBD proteins in maize might play a role in reading cytosine methylation. Taken together, these results would provide an important theoretical basis for future functional verification of ZmMBD genes and also facilitate future experimental research to further unravel the mechanisms of epigenetic regulation in plants.

中文翻译：

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苗期非生物胁迫处理玉米MBD基因家族全基因组分析及表达谱

植物中的甲基CpG结合结构域（MBD）蛋白是重要的反式作用因子，专门识别甲基化的DNA。MBD蛋白可以通过募集含有组蛋白脱乙酰基酶活性和染色质重塑因子的染色质修饰复合物来压紧染色质，从而抑制转录，并在植物的生长发育中发挥至关重要的生物学作用。当前，关于植物中MBD基因的结构和功能的了解很少。在这项研究中，我们从最新版本的玉米（B73）基因组中对玉米MBD基因（ZmMBDs）进行了全基因组鉴定和表达谱分析。通过分析拟南芥MBD基因家族的系统发育关系，水稻，小麦和玉米，玉米中的所有14种MBD蛋白都分为四个亚类。此外，染色体的位置和示意性结构分别揭示了玉米中MBD基因的染色体和结构特征的不均匀分布。最终，通过热，干旱和盐胁迫处理在幼苗叶片和茎中检测到的EST表达数据挖掘，微阵列数据聚类分析以及半定量和定量表达谱分析表明，这些基因具有时空表达模式并表现出在高温，干旱和盐胁迫条件下的不同表达水平，表明MBD的功能多样化玉米基因家族。此外，通过电泳迁移率变动分析（EMSA），代表性的MBD蛋白ZmMBD11具有体外DNA结合活性，表明玉米中的MBD蛋白可能在读取胞嘧啶甲基化中起作用。综上所述，这些结果将为将来的ZmMBD基因功能验证提供重要的理论基础，并有助于将来的实验研究以进一步阐明植物的表观遗传调控机制。