to histone modification and, if further epigenetic modification occurs, heterochromatin formation. This process is not well understood, as almost all information regarding it comes to us from the study of the FWA gene in Arabidopsis thaliana, a relatively TE-poor example in the plant kingdom. This paucity of information is further complicated by the relatively small genome and the low variability of the Arabidopsis epigenetic code. In general, initiation of transposon silencing has yet to be fully explained. For example, there have been recorded incidences of spontaneous silencing in maize, which carries a high number of transposons (~85% of the genome), though the mechanism by which this occurs is unknown. While it is known that heritable methylation occurs, and must occur with frequency, and must be initiated, triggered by some distinct factor, the only known example of this is in the case of Mu killer (Muk), a gene in maize that silences MuDR, a class II autonomous transposable element. Muk encodes a natural inverted derivative of the transposase coding sequence in MuDR, which, when transcribed, forms a dsRNA that is subsequently cut into siRNA, which renders MUDR incapable of 'cutting and pasting' itself by way of RNAi interference of the transposase. Muk also engages RNAi-Directed Methylation to create a stable and heritable suppression. Mutualistic/Parasitic Interactions Though transposable elements were discovered due in large part to their deleterious effects, epigenetic research has shown that they may be, in some cases, beneficial to the host organism.(1,5) This research indicates that the distinction between those two aspects, mutualist and parasite, may be harder to accurately describe than was once thought. Mutualism The primary mutualistic interaction between transposon and host organism is in the formation of epialleles. True to the name, an epiallele is a kind of epigenetic mutant of a certain allelic type that produces distinct morphological differences from the wild type. The predominant research into this subject has been conducted on Arabidopsis thaliana, which has the dual disadvantages of being both TE-poor and an overly genetically stable organism. The manner of formation of epialleles is somewhat unclear, but it is thought to be due to the fact that some transposable elements, in stealing pieces of genetic code from their host organism, blend in so well as to confuse the host cellular machinery into thinking that its own genes are the transposons, which leads to epigenetic silencing of certain alleles, forming an epiallele. Some