Violations of Mendel’s laws: Epigenetic regulation of gene expression

Epigenetics is an exciting and rapidly evolving field that impacts basic science, clinical medicine and agriculture. Epigenetic regulation refers to heritable control mechanisms superimposed on the DNA sequence. We investigate the control of gene expression in plants using the regulated expression of the genes required for the biosynthesis of the purple anthocyanin pigments in maize. Anthocyanin pigments have provided excellent visual and molecular markers to geneticists who used these genes to discover a number of important epigenetic phenomena in plants such as the cycling of transposons between silent and active states, transgene silencing and paramutation. Paramutation is an interaction between alleles that causes a directed, heritable alteration in the expression of one allele. In my laboratory we are using a combination of genetic and molecular approaches to determine the underlying mechanisms associated with epigenetic control of gene expression. In my talk I will describe the various epigenetic phenomena, discuss models for how chromatin-level control can produce heritable changes in gene expression, and discuss evolutionary implications of this type of gene regulation. Current ideas are that these mechanisms may have evolved to regulate gene dosage, maintain genome integrity, and defend against viruses and invasive DNA.