Abstract
Polycomb group (PcG) proteins are evolutionarily conserved chromatin modifiers that regulate developmental pathways in plants. PcGs form nuclear multi-subunit Polycomb Repressive Complexes (PRCs). The PRC2 complex mediates gene repression via methylation of lysine 27 on histone H3, which consequently leads to chromatin condensation. In Arabidopsis thaliana, several PRC2 complexes with different compositions were identified, each controlling a particular developmental program. The core subunit FIE is crucial for PRC2 function throughout the plant life cycle, yet accurate information on its spatial and temporal localization was absent. This study focused on identifying FIE accumulation patterns, using microscopy and biochemical approaches. Analysing endogenous FIE and transgenic gFIE-green fluorescent protein fusion protein (gFIE-GFP) showed that FIE accumulates in the nuclei of every cell type examined. Interestingly, gFIE-GFP, as well as the endogenous FIE, also localized to the cytoplasm in all examined tissues. In both vegetative and reproductive organs, FIE formed cytoplasmic high-molecular-mass complexes, in parallel to the nuclear PRC2 complexes. Moreover, size-exclusion chromatography and bimolecular fluorescence complementation assays indicated that in inflorescences FIE formed a cytoplasmic complex with MEA, a PRC2 histone methyltransferase subunit. In contrast, CLF and SWN histone methyltransferases were strictly nuclear. Presence of PRC2 subunits in cytoplasmic complexes has not been previously described in plants. Our findings are in agreement with accumulating evidence demonstrating cytoplasmic localization and function of PcGs in metazoa. The cytosolic accumulation of PRC2 components in plants supports the model that PcGs have alternative non-nuclear functions that go beyond chromatin methylation.
Original language | English |
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Pages (from-to) | 6111-6123 |
Number of pages | 13 |
Journal | Journal of Experimental Botany |
Volume | 67 |
Issue number | 21 |
DOIs | |
State | Published - 1 Nov 2016 |
Bibliographical note
Publisher Copyright:© 2016 The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.
Funding
We thank Prof. Shaul Yalovsky, Dr Daria Bloch, Dr Tali Yahalom and Prof. Daniel Chamovitz for technical support and scientific discussions. We thank Yu-Hung Hung for technical assistance with photographing plants. We are thankful to Inbar Nevo-Yassaf and Rinat Semyatich for technical support and Sigal Rencus-Lazar for editing the manuscript. N.O. was supported by grants from Israel Science Foundation (ISF, 574/04 and 767/09).
Funders | Funder number |
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Israel Science Foundation | 574/04, 767/09 |
Keywords
- Cytoplasm
- FIE
- MEA
- PRC2
- PcG
- Polycomb complex