title: Locus- and Site-Specific DNA Methylation of 19 kDa Zein Genes in Maize.
abstract: An interesting question in maize development is why only a single zein gene is highly expressed in each of the 19-kDa zein gene clusters (A and B types), z1A2-1 and z1B4, in the immature endosperm. For instance, epigenetic marks could provide a structural difference. Therefore, we investigated the DNA methylation of the arrays of gene copies in both promoter and gene body regions of leaf (non-expressing tissue as a control), normal endosperm, and cultured endosperm. Although we could show that expressed genes have much lower methylation levels in promoter regions than silent ones in both leaf and normal endosperm, there was surprisingly also a difference in the pattern of the z1A and z1B gene clusters. The expression of z1B gene is suppressed by increased DNA methylation and activated with reduced DNA methylation, whereas z1A gene expression is not. DNA methylation in gene coding regions is higher in leaf than in endosperm, whereas no significant difference is observed in gene bodies between expressed and non-expressed gene copies. A median CHG methylation (25-30%) appears to be optimal for gene expression. Moreover, tissue-cultured endosperm can reset the DNA methylation pattern and tissue-specific gene expression. These results reveal that DNA methylation changes of the 19-kDa zein genes is subject to plant development and tissue culture treatment, but varies in different chromosomal locations, indicating that DNA methylation changes do not apply to gene expression in a uniform fashion. Because tissue culture is used to produce transgenic plants, these studies provide new insights into variation of gene expression of integrated sequences.
authors.affiliation: Institute of Crop Science, Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou, Zhejiang 310058, China.
authors.forename: Jian-Hong
authors.initials: JH
authors.lastname: Xu
authors.affiliation: Institute of Crop Science, Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou, Zhejiang 310058, China.
authors.forename: Ruixian
authors.initials: R
authors.lastname: Wang
authors.affiliation: Institute of Crop Science, Zhejiang Key Laboratory of Crop Germplasm, Zhejiang University, Hangzhou, Zhejiang 310058, China.
authors.forename: Xinxin
authors.initials: X
authors.lastname: Li
authors.affiliation: National Institute of Research and Development for Biological Sciences, Cluj-Napoca, Romania.
authors.forename: Mihai
authors.initials: M
authors.lastname: Miclaus
authors.affiliation: Waksman Institute of Microbiology, Rutgers, The State University of New Jersey, Piscataway, New Jersey, 08854, United States of America.
authors.forename: Joachim
authors.initials: J
authors.lastname: Messing
mesh_terms: D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics / Q000378:metabolism*; D019175:DNA Methylation; D056625:Endosperm / Q000235:genetics* / Q000378:metabolism; D044127:Epigenesis, Genetic; D018506:Gene Expression Regulation, Plant; D056426:Genetic Loci; D005810:Multigene Family; D016366:Open Reading Frames; D009928:Organ Specificity; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D046509:Tissue Culture Techniques; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism; D015028:Zein / Q000235:genetics* / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D015028:Zein