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Lecture by Dr. Nina V. Fedoroff, Willaman Professor of Life Sciences and Evan Pugh Professor, Huck Institutes of the Life Sciences (http://www.lsc.psu.edu/), Pennsylvania State University,  http://hils.psu.edu/lsc/fedoroff.html

Epigenetics is the analysis of genetic changes that are stable, often heritable, but not irreversible in the same sense as are base changes, insertions, deletions, and other rearrangements. Until just a few years ago -- somewhere between 5 and 10 -- this field was considered slightly disreputable. Anyone interested in DNA methylation, an epigenetic modification, wasnít quite taken seriously. But no longer. The analysis of epigenetic phenomena, particularly gene silencing, is not is suddenly one of the most exciting areas of contemporary biology -- both in plants and in animals. My purpose here is to give you a brief overview of epigenetic studies in plants, from their origins in the studies of McClintock and other maize geneticists, to contemporary applications in plant protection
I will start bybriefly describing two classicalmaize epigenetic systems and then touch on more recent observations. Development, of course, is an epigenetic phenomenon and we increasingly understand that setting up differential gene expression patterns and locking them in during development occur by different mechanisms and involve different genes. Iíve long thought that plants offer a unique opportunity to analyse epigenetic phenomena because they produce germcells repeatedly during development, making it possible occasionally to catch epigenetic mutations, or epimutations, in the germline for genetic analysis. There is some truth to this in the sense that there were well-develop genetic analyses of epigenetic phenomena in plants earlier than there were in other eukaryotic genetic systems. But I think that the differences are not fundamental. Recent progress in understanding position effect variegation and Polycomb gene function in Drosophila and of X- inactivation and imprinting in mammals has made it evident that the commonalities are greater than the differences.