Paramutation: epigenetic instructions passed across generations.

摘要: PARAMUTATION is the fascinating ability of specific DNA sequences to communicate in trans establish meiotically heritable expression states. Intriguingly, newly silenced continue issue instructions naive alleles subsequent generations. The term “paramutation” was first coined 1950s by Alexander Brink describe this puzzling phenomenon at r1 locus maize (Brink 1956); an interaction between heterozygotes led decreases gene one allele. Not only reduced state stable through meiosis, but also low-expressing allele could induce silencing another high-expressing frequency change 100% and stability lower than typical mutations; hence “paramutation.” A few years later, Ed Coe, Jr., described example which b1 (Coe 1959) Rudolf Hagemann interactions sulfurea tomato (Hagemann 1969). Since that time other examples paramutation have been identified species (reviewed Chandler Stam 2004; Mittelsten Scheid 2005; 2007), yet two loci where initially described, b1, remain most extensively characterized best understood. encode closely related, functionally equivalent transcription factors activate anthocyanin pigment biosynthetic pathway (Goff et al. 1990; Ludwig 1990). They are likely related each a duplication resulting from ancient allotetraploidization event during evolution (Gaut Doebley 1997). multiple with distinct patterns, regulate distribution pigments development (Styles 1973; Coe 1979). Recent work demonstrates key role for RNA mediating both paramutation, as mop1 encodes RNA-dependent polymerase (RDR; Alleman 2006) absolutely required (Dorweiler 2000). Yet, there striking differences properties hint mechanisms. In article, potential mechanisms discussed relative our current understanding interference (RNAi) transcriptional silencing.