title: Tissue-specific DNase l-sensitive sites of the maize P gene and their changes upon epimutation.
abstract: map has been developed of nuclease-hypersensitive sites of P-rr, the standard allele of the P-locus of Zea mays L. Using a traditional DNase I assay, eight such sites have been found that are specific for the expressing tissue and span a region of more than 25 kb of the P-locus, making it one of the largest plant genes yet described. The maps of the standard allele have also been compared with the recently described moderately stable P-pr allele, which arose from epimutation. Six of the eight sites exhibit the same tissue-specificity in P-pr plants, while two stay repressed as in non-expressing tissues of plants with the standard allele. Interestingly, the two repressed sites coincide with two hypermethylated restriction sites that have previously been correlated with the expression potential of the P-pr allele. On the other hand, four of the DNase I sites, coinciding with CpG islands that were not hypermethylated by the epimutation, also showed no differences in their sensitivity to DNase I between the standard allele and the P-pr allele. This suggests that the epimutation affects both site-specific methylation changes and a specific local chromatin structure of the P gene involved in its regulation.
authors.affiliation: Waksman Institute, Rutgers, The State University of New Jersey, PO Box 759, Piscataway, NJ 08855, USA.
authors.forename: G
authors.initials: G
authors.lastname: Lund
authors.forename: O
authors.initials: O
authors.lastname: Prem Das
authors.forename: J
authors.initials: J
authors.lastname: Messing