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 suvh2suvh9 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 suvh2suvh9 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 suvh2suvh9 plants. This might indicate a role of these SUVH proteins in Pol V complex recruitment.
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Acknowledgments We thank Beate Kamm, Christa Fricke and Inge Glaser for excellent technical assistance, Armin Meister and Rhonda Meyer for support with statistical data analysis and Ingo Schubert for critically reading the manuscript. We are grateful to Gunter Reuter for contribution of transgenic A. thaliana line containing the Pro35S-mycSUVH2 construct and critical reading of the manuscript. This work was supported by German research foundation (DFG) collaborative research centre (SFB) 648 ‘‘Molecular Mechanisms of Information Processing in Plants’’.
- RNA-directed DNA methylation
- SET domain protein
ASJC Scopus subject areas
- Agronomy and Crop Science
- Plant Science