Thon, M.R., Mitchell, T.K. and Dean, R. 2006. 8th European Conference on Fungal Genetics (ECFG). April 7-12, 2006. Vienna, Austria.
Transposable elements (TEs) are known to be major contributors to genome
evolution. Genome wide studies have shown that in fungi, TEs are usually
confined to distinct clusters within the genome. To better understand the role of
TEs in mediating genome rearrangement, gene duplication, and gene evolution,
we performed an in depth study of chromosome 7 of the rice blast fungus
Magnaporthe oryzae. Using chromosome 7 as a reference sequence, we
identified 21 statistically significant blocks of conserved synteny in Neurospora
crassa, 17 in Fusarium graminearum, and 2 in Aspergillus nidulans. In general,
the blocks were roughly co-linear and interspersed with intervening, non-
syntenic genes. TEs are predominantly restricted to three clusters located in
regions that lack conserved synteny. In contradiction to popular evolutionary
models as well as observations from other model organism genomes, we found a
positive correlation between recombination rate and the distribution of TE
clusters on chromosome 7. We grouped chromosome 7 genes into gene families
and identified orthologous genes in N. crassa and F. graminearum. We found
that the chromosomal regions defined by the TE clusters have more frequent
gene duplications and genes within the clusters are evolving at a faster rate.
Together, these data suggest that TEs have a profound impact on the M. oryzae
genome by creating localized segments with increased rates of chromosomal
rearrangements, gene duplications and gene evolution.