Sekhon, Rajandeep , Chopra, Surinder .
Distinct epigenetic states of sequences in promoter and intron produce tissue-specific expression patterns of a Myb transcription factor in maize.
In maize, pericarp color1 (p1) encodes an R2R3 Myb transcription factor and regulates red phlobaphene pigmentation in floral tissues. Multiple alleles of p1 differ remarkably with respect to their pericarp (seed coat) and cob glumes (lemma and palea) pigmentation patterns. We are using this system to understand the molecular mechanisms that govern tissue- and allele-specific expression in multi-cellular organisms. One of the p1 alleles, P1-wr, produces white pericarp and red cob glume phenotype that is stably inherited over generations. An unlinked dominant mutation, Unstable factor for orange1 (Ufo1) disrupts the stable expression pattern of P1-wr and leads to ectopic pigmentation of pericarp, cob glumes and vegetative tissues. We have previously demonstrated that gain of pericarp pigmentation in P1-wr Ufo1 plants is epigenetically regulated. This phenotype is correlated with decrease in DNA methylation of a distal enhancer element located in the promoter region. We have now characterized P1-wr*, a loss-of-function epiallele of P1-wr that is silenced in the pericarp as well as cob and thus produces a white pericarp and white cob glume phenotype. Remarkably, interaction of Ufo1 with P1-wr* leads to gain of cob pigmentation whereas pericarp of this allele remains colorless. Genomic bisulfite sequencing showed that gain of cob pigmentation in P1-wr* Ufo1 plants correlates with hypomethylation of a 168 bp sequence within second intron of the p1 gene. Interestingly, methylation of the distal enhancer element previously implicated in gain of pericarp pigmentation remained unchanged in P1-wr* Ufo1 plants. Our results suggest that epigenetic states of sequences that are several kilobase pairs apart regulate tissue-specific expression of the p1 gene.
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1 - The Pennsylvania State University, Crop and Soil Sciences, 116 Ag. Sci. Ind. Bldg., University Park, PA, 16802, USA
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM