Caister Academic Press

Repeat-induced Point Mutation, DNA Methylation and Heterochromatin in Gibberella zeae (anamorph: Fusarium graminearum)

Kyle R. Pomraning, Lanelle R. Connolly, Joseph P. Whalen, Kristina M. Smith and Michael Freitag
from: Fusarium: Genomics, Molecular and Cellular Biology (Edited by: Daren W. Brown and Robert H. Proctor). Caister Academic Press, U.K. (2013)

Abstract

Multiple mechanisms control genome stability in filamentous fungi. To limit the expansion of repeated DNA, e.g. transposable elements (TEs), a group of filamentous ascomycetes make use of a duplication-dependent mutator system, called "Repeat-Induced Point mutation" (RIP). This phenomenon was the first eukaryotic genome defense system identified and characterized in the 1980s by Selker and colleagues in pioneering studies with Neurospora crassa. RIP detects gene-sized duplications and aligns homologous copies by an unknown homology search mechanism during pre-meiosis. Transition mutations (C:G to T:A) are introduced, typically into both or all copies of the DNA segments. In 2007, RIP was first described in Gibberella zeae (anamorph: Fusarium graminearum) by Kistler and colleagues. Here we review previous experiments and add our recent data, which confirm that RIP occurs at relatively high frequencies in this homothallic species. We show that the G. zeae rid homologue is required for RIP, as had been found in N. crassa. In contrast to N. crassa, DNA methylation does not seem to be a common consequence of RIP. Lastly, we discuss potential evolutionary consequences of RIP in heterothallic and homothallic fungi read more ...
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