A role for CHROMOMETHYLASE3 in mediating transposon and euchromatin silencing during egg cell reprogramming in Arabidopsis.
During embryogenesis there is a major switch from dependence upon maternally-deposited products to reliance on products of the zygotic genome. In animals, this so-called maternal-to-zygotic transition occurs following a period of transcriptional quiescence. Recently, we have shown that the early embryo in Arabidopsis is also quiescent, a state inherited from the female gamete and linked to specific patterns of H3K9 dimethylation and TERMINAL FLOWER2 (TFL2) localization. We also demonstrated that CHROMOMETHYLASE 3 (CMT3) is required for H3K9 dimethylation in the egg cell and for normal embryogenesis during the first few divisions of the zygote. Subsequent analysis of CMT3 mutants points to a key role in egg cell reprogramming by controlling silencing in both transposon and euchromatic regions. A speculative model of the CMT3-induced egg cell silencing is presented here, based on these results and current data from the literature suggesting the potential involvement of small RNAs targeted to the egg cell, a process conceptually similar to the division of labor described in the male gametophyte for which we show that H3K9 modifications and TFL2 localization are reminiscent of the female gametophyte.
Pillot
Marion
M
Laboratoire Génome et Développement des Plantes (LGDP), UMR 5096 IRD-CNRS-Université de Perpignan, Montpellier, France.
Autran
Daphné
D
Leblanc
Olivier
O
Grimanelli
Daniel
D
D000107:Acetylation; D017360:Arabidopsis / Q000166:cytology / Q000196:embryology / Q000201:enzymology* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D065150:Cellular Reprogramming; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D019175:DNA Methylation; D004251:DNA Transposable Elements / Q000235:genetics*; D015257:DNA-Cytosine Methylases / Q000378:metabolism*; D022041:Euchromatin / Q000235:genetics*; D020868:Gene Silencing; D006657:Histones / Q000378:metabolism; D008954:Models, Biological; D056771:Ovule / Q000166:cytology; D010063:Ovum / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D021381:Protein Transport; D018749:RNA, Plant / Q000378:metabolism
D029681:Arabidopsis Proteins; D002868:Chromosomal Proteins, Non-Histone; D004251:DNA Transposable Elements; D015257:DNA-Cytosine Methylases; D022041:Euchromatin; D006657:Histones; D018749:RNA, Plant; C477788:At5g17690 protein, Arabidopsis; C429766:CMT3 protein, Arabidopsis