Overexpression of a methyl-CpG-binding protein gene OsMBD707 leads to larger tiller angles and reduced photoperiod sensitivity in rice

Background Methyl-CpG-binding domain (MBD) proteins play important roles in epigenetic gene regulation, and have diverse molecular, cellular, and biological functions in plants. MBD proteins have been functionally characterized in various plant species, including Arabidopsis, wheat, maize, and tomato. In rice, 17 sequences were bioinformatically predicted as putative MBD proteins. However, very little is known regarding the function of MBD proteins in rice. Results We explored the expression patterns of the rice OsMBD family genes and identified 13 OsMBDs with active expression in various rice tissues. We further characterized the function of a rice class I MBD protein OsMBD707, and demonstrated that OsMBD707 is constitutively expressed and localized in the nucleus. Transgenic rice overexpressing OsMBD707 displayed larger tiller angles and reduced photoperiod sensitivity—delayed flowering under short day (SD) and early flowering under long day (LD). RNA-seq analysis revealed that overexpression of OsMBD707 led to reduced photoperiod sensitivity in rice and to expression changes in flowering regulator genes in the Ehd1-Hd3a/RFT1 pathway. Conclusion The results of this study suggested that OsMBD707 plays important roles in rice growth and development, and should lead to further studies on the functions of OsMBD proteins in growth, development, or other molecular, cellular, and biological processes in rice.

Overexpression of a methyl-CpG-binding Protein Gene OsMBD707, Leads to Larger Tiller Angles and Reduced Photoperiod Sensitivity in Rice

Background: Methyl-CpG-binding domain (MBD) proteins play important roles in epigenetic gene regulation, and have diverse molecular, cellular, and biological functions in plants. MBD proteins have been functionally characterized in various plant species, including Arabidopsis, wheat, maize, and tomato. In rice, 17 sequences were bioinformatically predicted as putative MBD proteins. However, very little is known regarding the function of MBD proteins in rice.Results: We explored the expression patterns of the rice OsMBD family genes and identified 13 OsMBDs with active expression in various rice tissues. We further characterized the function of a rice class I MBD protein OsMBD707, and demonstrated that OsMBD707 is constitutively expressed and localized in the nucleus. Transgenic rice overexpressing OsMBD707 displayed larger tiller angles and reduced photoperiod sensitivity—delayed flowering under short day (SD) and early flowering under long day (LD). RNA-seq analysis revealed that overexpression of OsMBD707 led to reduced photoperiod sensitivity in rice through regulating expression of key flowering regulator genes in the Ehd1-Hd3a/RFT1 pathway.Conclusion: The results of this study demonstrated that OsMBD707 plays important roles in rice growth and development, and should lead to further studies on the functions of OsMBD proteins in growth, development, or other molecular, cellular, and biological processes in rice.

Role of MBD2 in gene regulation and tumorigenesis

DNA methylation is an epigenetic mechanism involved in transcriptional silencing of imprinted genes, genes located on the inactive X chromosome, and a number of tumour suppressor genes in cancer. MBD (methyl-CpG-binding domain) proteins selectively bind to methylated DNA and recruit chromatin remodelling and transcriptional repressor complexes, thereby establishing a repressive chromatin state. MBD2, a member of the MBD protein family, binds to methylated promoter CpG islands (clusters of high-density CpG dinucleotides) and acts as a methylation-dependent transcriptional repressor. Previous work has demonstrated that decreased CpG island methylation in mice lacking the DNA methyltransferase DNMT1 is associated with impaired tumorigenesis when crossed on the tumour-susceptible ApcMin/+ background. Mbd2 deficiency also dramatically reduces adenoma burden and extends life span in a gene dosage-dependent manner in this mouse model. Mbd2 is therefore essential for tumorigenesis in the murine intestine, although it is dispensable for the viability of the host animals. These findings validate MBD2 as a potential target for therapeutic intervention in colorectal cancer.

DNA Methylation Is Linked to Deacetylation of Histone H3, but Not H4, on the Imprinted Genes Snrpnand U2af1-rs1

ABSTRACT The relationship between DNA methylation and histone acetylation at the imprinted mouse genes U2af1-rs1 and Snrpnis explored by chromatin immunoprecipitation (ChIP) and resolution of parental alleles using single-strand conformational polymorphisms. TheU2af1-rs1 gene lies within a differentially methylated region (DMR), while Snrpn has a 5′ DMR (DMR1) with sequences homologous to the imprinting control center of the Prader-Willi/Angelman region. For both DMR1 of Snrpn and the 5′ untranslated region (5′-UTR) and 3′-UTR ofU2af1-rs1, the methylated and nonexpressed maternal allele was underacetylated, relative to the paternal allele, at all H3 lysines tested (K14, K9, and K18). For H4, underacetylation of the maternal allele was exclusively (U2af1-rs1) or predominantly (Snrpn) at lysine 5. Essentially the same patterns of differential acetylation were found in embryonic stem (ES) cells, embryo fibroblasts, and adult liver from F1 mice and in ES cells from mice that were dipaternal or dimaternal for U2af1-rs1. In contrast, in a region within Snrpn that has biallelic methylation in the cells and tissues analyzed, the paternal (expressed) allele showed relatively increased acetylation of H4 but not of H3. The methyl-CpG-binding-domain (MBD) protein MeCP2 was found, by ChIP, to be associated exclusively with the maternal U2af1-rs1 allele. To ask whether DNA methylation is associated with histone deacetylation, we produced mice with transgene-induced methylation at the paternal allele of U2af1-rs1. In these mice, H3 was underacetylated across both the parental U2af1-rs1 alleles whereas H4 acetylation was unaltered. Collectively, these data are consistent with the hypothesis that CpG methylation leads to deacetylation of histone H3, but not H4, through a process that involves selective binding of MBD proteins.