Tissue-specific patterns of a maize Myb transcription factor are epigenetically regulated

Abstract

<p>The maize <em>p1</em> gene encodes a <em>Myb</em>-homologous regulator of red pigment biosynthesis. To investigate the tissue-specific regulation of the <em>p1</em> gene, maize plants were transformed with constructs combining promoter and cDNA sequences of two alleles which differ in pigmentation patterns: <em>P1-wr</em> (white pericarp/red cob) and <em>P1-rr</em> (red pericarp/red cob). Surprisingly, all promoter/cDNA combinations produced transgenic plants with red pericarp and red cob (RR pattern), indicating that the <em>P1-wr</em> promoter and encoded protein can function in pericarp. Some of the RR patterned transgenic plants produced progeny plants with white pericarp and red cob (WR pattern), and this switch in tissue-specificity correlated with increased transgene methylation. A similar inverse correlation between pericarp pigmentation and DNA methylation was observed for certain natural <em>p1</em> alleles, which have a gene structure characteristic of standard <em>P1-wr</em> alleles, but which confer red pericarp pigmentation and are consistently less methylated than standard <em>P1-wr</em> alleles. Although we cannot rule out the possible existence of tissue-specific regulatory elements within the <em>p1</em> non-coding sequences or flanking regions, the data from transgenic and natural alleles suggest that the tissue-specific pigmentation pattern characteristic of the <em>P1-wr</em>phenotype is epigenetically controlled.</p>