Abstract
In plants, RNA-directed DNA methylation (RdDM) and related transcriptional gene silencing (TGS) involve members of the suppressor of variegation 3-9-homologous (SUVH) group of putative histone methyltransferases. Utilizing a reverse genetic approach in
Arabidopsis thaliana
, we demonstrate that two closely related
SUVH
members,
SUVH2
and
SUVH9
, act partially non-redundant in RdDM. DNA methylation, transcript accumulation and association with histone modifications were analyzed at the endogenous RdDM target
AtSN1
(a SINE-like retroelement) in
suvh2
and
suvh9
single as well as
suvh2
suvh9
double mutants.
SUVH2
was found to be required for full DNA methylation at
AtSN1
in early seed development and was also higher expressed in seeds than at later developmental stages.
SUVH9
had its impact on RdDM later during vegetative development of the plant and was also higher expressed during that stage than at earlier developmental stages. The strongest reduction of RdDM at
AtSN1
was found in
suvh2
suvh9
double mutant plants. Histone 3-lysine 9-dimethylation (H3K9me2) associated with
AtSN1
was reduced only in the simultaneous absence of functional
SUVH2
and
SUVH9
. Thus,
SUVH2
and
SUVH9
functions in RdDM and TGS are overlapping in spite of some developmental specialization. Pol V specific transcripts were reduced in
suvh2
suvh9
plants. This might indicate a role of these SUVH proteins in Pol V complex recruitment.