P1-Bh: A Maize Regulatory Gene Controlled by DNA Methylation

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This project will focus upon the molecular and genetic analysis of Pl-Bh, a gene which controls the synthesis of purple anthocyanin pigments in the maize plant. Preliminary analysis indicates that at the nucleotide level, this gene is nearly identical to the wild- type Pl gene but, unlike that gene, is heavily methylated. The planned experiments will test the hypothesis that methylation of the Pl-Bh DNA is responsible for the variegated pattern of expression or the altered tissue-specificity of this allele or both. The methylation status will be determined using genomic sequencing methods and will be correlated with the level of gene expression in lightly pigmented and darkly pigmented cells from plant and kernel tissues. Possible alterations in chromatin configuration and/or protein-DNA contacts will be analyzed by DNase footprinting. Both the wild-type and mutant genes will be introduced into various tissues by microprojectile bombardment and their expression correlated with phenotypic differences. We will look for genetic modifiers of the mutant allele and it will be determined if the modification is a result of alterations in the methylation pattern of the Pl-Bh allele. %%% DNA methylation plays an important role in the regulation of gene expression in many eukaryotes, usually by silencing gene expression. In only a few cases has it been shown to influence the tissue-specificity of expression. The results of these experiments should serve to enhance our understanding of this and other epigenetic mechanisms which modulate plant gene expression. $$$