title: Epigenetic modifications of distinct sequences of the p1 regulatory gene specify tissue-specific expression patterns in maize.
abstract: Tandemly repeated endogenous genes are common in plants, but their transcriptional regulation is not well characterized. In maize, the P1-wr allele of pericarp color1 is composed of multiple copies arranged in a head-to-tail fashion. P1-wr confers a white kernel pericarp and red cob glume pigment phenotype that is stably inherited over generations. To understand the molecular mechanisms that regulate tissue-specific expression of P1-wr, we have characterized P1-wr*, a spontaneous loss-of-function epimutation that shows a white kernel pericarp and white cob glume phenotype. As compared to its progenitor P1-wr, the P1-wr* is hypermethylated in exon 1 and intron 2 regions. In the presence of the epigenetic modifier Ufo1 (Unstable factor for orange1), P1-wr* plants exhibit a range of cob glume pigmentation whereas pericarps remain colorless. In these plants, the level of cob pigmentation directly correlates with the degree of DNA demethylation in the intron 2 region of p1. Further, genomic bisulfite sequencing indicates that a 168-bp region of intron 2 is significantly hypomethylated in both CG and CNG context in P1-wr* Ufo1 plants. Interestingly, P1-wr* Ufo1 plants did not show any methylation change in a distal enhancer region that has previously been implicated in Ufo1-induced gain of pericarp pigmentation of the P1-wr allele. These results suggest that distinct regulatory sequences in the P1-wr promoter and intron 2 regions can undergo independent epigenetic modifications to generate tissue-specific expression patterns.
authors.affiliation: Department of Crop and Soil Sciences, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Rajandeep S
authors.initials: RS
authors.lastname: Sekhon
authors.forename: Thomas
authors.initials: T
authors.lastname: Peterson
authors.forename: Surinder
authors.initials: S
authors.lastname: Chopra
mesh_terms: D001483:Base Sequence; D003433:Crosses, Genetic; D019175:DNA Methylation; D044127:Epigenesis, Genetic / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009693:Nucleic Acid Hybridization; D010641:Phenotype; D010858:Pigmentation / Q000235:genetics; D012150:Polymorphism, Restriction Fragment Length; D017422:Sequence Analysis, DNA; D020080:Tandem Repeat Sequences / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics; D003313:Zea mays / Q000235:genetics*
chemical_list: D014157:Transcription Factors; C480438:Ufo1 protein, maize