Histone acetylation/deacetylation represent a general and
efficient epigenetic mechanism through which fungal cells control
gene expression. Here we report developmental requirement
of MoHOS2-mediated histone deacetylation (HDAC)
for the rice blast fungus, Magnaporthe oryzae. Structural similarity
and nuclear localization indicated that MoHOS2 is an
ortholog of Saccharomyces cerevisiae Hos2, which is a member
of class I histone deacetylases and subunit of Set3 complex.
Deletion of MoHOS2 led to 25% reduction in HDAC
activity, compared to the wild-type, confirming that it is a
bona-fide HDAC. Lack of MoHOS2 caused decrease in radial
growth and impinged dramatically on asexual sporulation.
Such reduction in HDAC activity and phenotypic defects of
ΔMohos2 were recapitulated by a single amino acid change
in conserved motif that is known to be important for HDAC
activity. Expression analysis revealed up-regulation of MoHOS2
and concomitant down-regulation of some of the key genes
involved in asexual reproduction under sporulation-promoting
condition. In addition, the deletion mutant exhibited defect
in appressorium formation from both germ tube tip and
hyphae. As a result, ΔMohos2 was not able to cause disease
symptoms. Wound-inoculation showed that the mutant is
compromised in its ability to grow inside host plants as well.
We found that some of ROS detoxifying genes and known
effector genes are de-regulated in the mutant. Taken together,
our data suggest that MoHOS2-dependent histone deacetylation
is pivotal for proper timing and induction of transcription
of the genes that coordinate developmental changes
and host infection in M. oryzae.