The expression of phytohemagglutinin genes in Phaseolus vulgaris is associated with organ-specific DNA methylation patterns.

Using methylation sensitive restriction enzymes and DNA gel blot analyses, we have examined DNA methylation patterns at the chromosomal locus harboring the two phytohemagglutinin genes of Phaseolus vulgaris. In cotyledons, where the genes are highly expressed, several sites have become undermethylated, whereas the methylation status of other sites remains constant, both in cotyledons and in other organs. Taken together with measurements of mRNA levels, these studies provide evidence that organ-specific changes in DNA methylation patterns are associated with the organ-specific expression of nuclear genes in a dicotyledonous plant.