Associated Faculty
Plant genome sizes can vary several orders of magnitude between species. Such differences are due in many cases to polyploidy but, more generally, to differences in the amount of repetitive DNA present in the genome. Pablo Rabinowicz is interested in the mechanisms that allow plants to tolerate such large amounts of DNA, mainly retrotransposable elements, which are targets of epigenetic silencing.
Retrotransposon expansions often occur relatively rapidly and, therefore, one of the problems that the cell has to deal with is the replication of an increased amount of DNA. The mechanism by which the location of origins of DNA replication is specified in eukaryotes is largely unknown. With the exception of yeast autonomously replicating sequences (ARS), no consensus DNA sequence has been identified in eukaryotic origins. Interestingly, the average length of the genomic regions replicated from a single origin (replicons) does not increase proportionally to genome size.
For example, in related plants showing genome size
differences of 2 orders of magnitude, replicon sizes vary only up to 2-fold.
The fact that retrotransposons have been related to origin location, and the
growing amount of evidence of the involvement of epigenetic mechanisms in the
process of replication origin specification, make retrotransposons good
candidates to play a role in the process of origin specification.
Dr. Rabinowicz is using next-generation sequencing technologies to obtain
genome-wide profiles of DNA methylation as well as other epigenetic features to
correlate them with the presence of DNA replication origins in related genomes
of different size. These studies will shed light on the basic process of
eukaryotic origin specification.
