Plant & Animal Genomes XIV Conference Plant & Animal Genomes XIV ConferenceJanuary 14-18, 2006
Town & Country Convention Center
San Diego, CA
The extensive lack of collinearity among allelic maize genomic segments has recently been described. Two types of phenomena are responsible for this observation: presence/absence of LTR-retrotransposons and presence/absence of genic fragments. Retrotransposons that are not shared between inbred lines appear to have inserted into the maize genome significantly more recently than those that are shared, revealing an active movement of high copy number elements in very recent evolutionary times. The genic fragment polymorphisms are also due to recent insertions of non autonomous elements of the helitron class as well as of the CACTA class. It has often been postulated that transposable elements are still actively reshaping genomes: the maize genome is in constant flux in that transposable elements continue changing both the genic and non-genic fraction of the genome, profoundly affecting genetic diversity. In addition to the non colinearity we have detected extensive cis-regulatory variation in maize genes, including what we called expression overdominance. We will discuss the implications of the allelic non collinearities for regulatory variation, heterosis and evolution of novel gene functions. We will examine the possibility that, as predicted by Orgel and Crick early on, the host organism, maize in our case, may have found some use for some of the selfish DNA sequences, namely for control purposes at one level or another.