The effects of histone acetylation on the maize allele PL1-blotched

Covalent modifications of DNA and nucleosomal histone proteins associated with eukaryotic chromatin have the potential to alter expression of a gene without change in its DNA sequence. One gene regulated through this so-called epigenetic process is the Pl1Blotched gene of maize. Pl1-Blotched is a allele of the purple1 (pl1) gene, which encodes a transcription factor that activates synthesis of purple anthocyanin pigments. Pl1Blotched is unusual in that it leads to variegated, rather than uniform, pigmentation. At the molecular level, this phenotype is associated with low expression of pl1 mRNA, a novel pattern of DNA methylation and condensed chromatin structure. To ask if acetylation of nucleosomal histone proteins might be involved in regulating the chromatin organization of Pl1-Blotched, this allele was crossed into 40 lines containing transgenes that target reduction of various histone acetyltransferase and histone deacetylase genes. Some of the lines led to altered Pl1-Blotched pigmentation. Detailed analysis of molecular changes underlying the altered pigmentation resulted in models that implicate both histone acetyltransferase and histone deacetylase genes in controlling expression of Pl1-Blotched. These findings lay the foundation for future studies aimed at further understanding the interplay between histone modification and regulation of gene expression.