Title: Interaction of the Arabidopsis Polycomb group proteins FIE and MEA mediates their common phenotypes
Abstract: Genes of the FERTILISATION INDEPENDENT SEED (FIS) class regulate cell proliferation during reproductive development in Arabidopsis[1Chaudhury AM Ming L Miller C Craig S Dennis ES Peacock WJ Fertilization-independent seed development in Arabidopsis thaliana.Proc Natl Acad Sci USA. 1997; 94: 4223-4228Crossref PubMed Scopus (383) Google Scholar, 2Ohad N Margossian Y Hsu Y-C Williams C Repetti P Fischer RL A mutation that allows endosperm development without fertilisation.Proc Natl Acad Sci USA. 1996; 93: 5319-5324Crossref PubMed Scopus (302) Google Scholar, 3Grossniklaus U Vielle-Calzada JP response: parental conflict and infanticide during embryogenesis.Trends Plant Sci. 1998; 3: 328Abstract Full Text Full Text PDF Scopus (20) Google Scholar, 4Grossniklaus U VielleCalzada JP Hoeppner MA Gagliano WB Maternal control of embryogenesis by MEDEA, a Polycomb group gene in Arabidopsis.Science. 1998; 280: 446-450Crossref PubMed Scopus (674) Google Scholar, 5Kiyosue T Ohad N Yadegari R Hannon M Dinneny J Wells D et al.Control of fertilization-independent endosperm development by the MEDEA polycomb gene Arabidopsis.Proc Natl Acad Sci USA. 1999; 96: 4186-4191Crossref PubMed Scopus (266) Google Scholar]. The FIS genes FERTILISATION INDEPENDENT ENDOSPERM (FIE) and MEDEA (MEA) encode homologs of animal Polycomb group (Pc-G) proteins, transcriptional regulators that modify chromatin structure and are thought to form multimeric complexes [3Grossniklaus U Vielle-Calzada JP response: parental conflict and infanticide during embryogenesis.Trends Plant Sci. 1998; 3: 328Abstract Full Text Full Text PDF Scopus (20) Google Scholar, 4Grossniklaus U VielleCalzada JP Hoeppner MA Gagliano WB Maternal control of embryogenesis by MEDEA, a Polycomb group gene in Arabidopsis.Science. 1998; 280: 446-450Crossref PubMed Scopus (674) Google Scholar, 5Kiyosue T Ohad N Yadegari R Hannon M Dinneny J Wells D et al.Control of fertilization-independent endosperm development by the MEDEA polycomb gene Arabidopsis.Proc Natl Acad Sci USA. 1999; 96: 4186-4191Crossref PubMed Scopus (266) Google Scholar, 6Luo M Bilodeau P Koltunow A Dennis ES Peacock WJ Chaudhury AM Genes controlling fertilization-independent seed development in Arabidopsis thaliana.Proc Natl Acad Sci USA. 1999; 96: 296-301Crossref PubMed Scopus (357) Google Scholar, 7Ohad N Yadegari R Margossian L Hannon M Michaeli D Harada JJ et al.Mutations in FIE, a WD polycomb group gene, allow endosperm development without fertilization.Plant Cell. 1999; 11: 407-415PubMed Google Scholar, 8Tie F Furuyama T Harte PJ The Drosophila Polycomb Group proteins ESC and E(Z) bind directly to each other and co-localize at multiple chromosomal sites.Development. 1998; 125: 3483-3496PubMed Google Scholar, 9Jones CA Ng J Peterson AJ Morgan K Simon J Jones RS The Drosophila ESC and E(Z) proteins are direct partners in Polycomb group-mediated repression.Mol Cell Biol. 1998; 18: 2825-2834Crossref PubMed Google Scholar, 10Shao Z Raible F Mollaaghababa R Guyon JR Wu C-T Bender W Kingston RE Stabilisation of chromatin structure by PRC1, a Polycomb complex.Cell. 1999; 98: 37-46Abstract Full Text Full Text PDF PubMed Scopus (640) Google Scholar, 11van der Vlag J Otte AP Transcriptional repression mediated by the human polycomb-group protein EED involves histone deacetylation.Nat Genet. 1999; 23: 474-478Crossref PubMed Scopus (438) Google Scholar]. To test whether similarities in fis mutant phenotypes reflect interactions between their protein products, we characterised FIE RNA and protein localisation in vivo, and FIE protein interactions in yeast and in vitro. Expression of FIE mRNA overlaps with that of MEA during embryo sac and seed development and is unaffected in mea mutants. Results from the yeast two-hybrid system and an in vitro pull-down assay indicate that MEA and FIE proteins interact. The relevance of this interaction in vivo is supported by the finding that FIE and MEA co-localise in the nucleus in transfected plant cells. Interaction of MEA and FIE is mediated by the amino-terminal region of MEA. Despite sequence divergence in this domain, MEA can interact with its corresponding animal partner Extrasexcombs (ESC) in the yeast two-hybrid system. We conclude that FIE and MEA act together as part of a multimeric complex and that this accounts for the similarities in mutant phenotypes. We propose that an ancient mechanism for chromatin modification has been independently recruited to different developmental processes in the two kingdoms.