title: A maize Myb homolog is encoded by a multicopy gene complex.
abstract: The maize P gene encodes a Myb-homologous transcriptional regulator of flavonoid pigmentation in floral organs, and different P gene alleles condition precise tissue- and organ-specific pigmentation patterns. To determine the molecular basis for allele-specific expression patterns, we have isolated and compared two natural alleles of the P gene which differ in expression, structure and copy number. The P-rr allele is associated with pigmentation of most floral tissues and contains a single copy of the P gene. In contrast, the P-wr allele restricts pigmentation to a subset of floral tissues, and is composed of six gene copies arranged in a tandem head-to-tail array. Each of the six repeats contains a single P gene, including regulatory and coding sequences. Despite the six-fold tandem repetition of P-wr gene copies, P-wr mRNA levels in kernel pericarp are much reduced compared to mRNA levels from the single-copy P-rr gene. Moreover, the P-wr multicopy complex is hypermethylated relative to P-rr. Thus, maize P gene alleles may represent a natural system for studying the effects of methylation and gene copy number on tissue-specific gene expression. We discuss the possibility that somatic pairing of repeated gene copies may be involved in regulating gene expression.
authors.affiliation: Department of Zoology and Genetics, Iowa State University, Ames 50011, USA.
authors.forename: S
authors.initials: S
authors.lastname: Chopra
authors.forename: P
authors.initials: P
authors.lastname: Athma
authors.forename: X G
authors.initials: XG
authors.lastname: Li
authors.forename: T
authors.initials: T
authors.lastname: Peterson
mesh_terms: D000483:Alleles; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000235:genetics*; D005419:Flavonoids / Q000096:biosynthesis; D018628:Gene Dosage; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D009857:Oncogenes; D010860:Pigments, Biological; D010940:Plant Proteins / Q000235:genetics*; D018520:Plant Shoots; D012091:Repetitive Sequences, Nucleic Acid; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D003313:Zea mays / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D005419:Flavonoids; C085863:P protein, Zea mays; D010860:Pigments, Biological; D010940:Plant Proteins