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Overexpression of AtBMI1C, a polycomb group protein gene, accelerates flowering in Arabidopsis.

Li W, Wang Z, Li J, Yang H, Cui S, Wang X, Ma L - PLoS ONE (2011)

Bottom Line: No change in the H3K27me3 level in FLC chromatin was detected in an AtBMI1C-overexpressing line.Our results suggest that AtBMI1C participates in flowering time control by regulating the expression of FLC; moreover, the repression of FLC by AtBMI1C is not due to the activity of PRC2.Instead, it is likely the result of PRC1 activity, into which AtBMI1C is integrated.

View Article: PubMed Central - PubMed

Affiliation: Hebei Key Laboratory of Molecular Cell Biology, College of Biological Sciences, Hebei Normal University, Shijiazhuang, Hebei, China.

ABSTRACT
Polycomb group protein (PcG)-mediated gene silencing is emerging as an essential developmental regulatory mechanism in eukaryotic organisms. PcGs inactivate or maintain the silenced state of their target chromatin by forming complexes, including Polycomb Repressive Complex 1 (PRC1) and 2 (PRC2). Three PRC2 complexes have been identified and characterized in Arabidopsis; of these, the EMF and VRN complexes suppress flowering by catalyzing the trimethylation of lysine 27 on histone H3 of FLOWER LOCUS T (FT) and FLOWER LOCUS C (FLC). However, little is known about the role of PRC1 in regulating the floral transition, although AtRING1A, AtRING1B, AtBMI1A, and AtBMI1B are believed to regulate shoot apical meristem and embryonic development as components of PRC1. Moreover, among the five RING finger PcGs in the Arabidopsis genome, four have been characterized. Here, we report that the fifth, AtBMI1C, is a novel, ubiquitously expressed nuclear PcG protein and part of PRC1, which is evolutionarily conserved with Psc and BMI1. Overexpression of AtBMI1C caused increased H2A monoubiquitination and flowering defects in Arabidopsis. Both the suppression of FLC and activation of FT were observed in AtBMI1C-overexpressing lines, resulting in early flowering. No change in the H3K27me3 level in FLC chromatin was detected in an AtBMI1C-overexpressing line. Our results suggest that AtBMI1C participates in flowering time control by regulating the expression of FLC; moreover, the repression of FLC by AtBMI1C is not due to the activity of PRC2. Instead, it is likely the result of PRC1 activity, into which AtBMI1C is integrated.

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Nuclear localization and expression pattern of AtBMI1C. (A) Images of roots from transgenic seedlings harboring YFP driven by the CaMV35S promoter. (B) Images of roots from transgenic seedlings harboring YFP-tagged AtBMI1C driven by the CaMV35S promoter. Scale bar (red), 100 µm. (C) Images of petals from transgenic plants harboring YFP-tagged AtBMI1C driven by the CaMV35S promoter. Scale bar (red), 50 µm. (D) The expression pattern of AtBMI1C in seedlings and different organs was analyzed by semiquantitative RT-PCR.
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pone-0021364-g002: Nuclear localization and expression pattern of AtBMI1C. (A) Images of roots from transgenic seedlings harboring YFP driven by the CaMV35S promoter. (B) Images of roots from transgenic seedlings harboring YFP-tagged AtBMI1C driven by the CaMV35S promoter. Scale bar (red), 100 µm. (C) Images of petals from transgenic plants harboring YFP-tagged AtBMI1C driven by the CaMV35S promoter. Scale bar (red), 50 µm. (D) The expression pattern of AtBMI1C in seedlings and different organs was analyzed by semiquantitative RT-PCR.

Mentions: The expression pattern and subcellular localization of AtBMI1C were examined to elucidate the biological functions of the protein. To determine the subcellular localization of AtBMI1C, a reporter gene (Yellow Fluorescence Protein [YFP]) was fused to the AtBMI1C coding region under the control of the CAULIFLOWER MOSAIC VIRUS (CaMV) 35S promoter to generate stable transgenic plants carrying p35S::AtBMI1C-YFP or p35S::YFP (control). YFP signals were detected in the nucleus and cytoplasm in the roots of p35S::YFP transgenic plants (Figure 2A); in comparison, YFP signals in the roots or petals of p35S::AtBMI1C-YFP transgenic plants were detected only in the nucleus (Figure 2B and C). Thus, AtBMI1C encodes a nuclear-localized protein.


Overexpression of AtBMI1C, a polycomb group protein gene, accelerates flowering in Arabidopsis.

Li W, Wang Z, Li J, Yang H, Cui S, Wang X, Ma L - PLoS ONE (2011)

Nuclear localization and expression pattern of AtBMI1C. (A) Images of roots from transgenic seedlings harboring YFP driven by the CaMV35S promoter. (B) Images of roots from transgenic seedlings harboring YFP-tagged AtBMI1C driven by the CaMV35S promoter. Scale bar (red), 100 µm. (C) Images of petals from transgenic plants harboring YFP-tagged AtBMI1C driven by the CaMV35S promoter. Scale bar (red), 50 µm. (D) The expression pattern of AtBMI1C in seedlings and different organs was analyzed by semiquantitative RT-PCR.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3119047&req=5

pone-0021364-g002: Nuclear localization and expression pattern of AtBMI1C. (A) Images of roots from transgenic seedlings harboring YFP driven by the CaMV35S promoter. (B) Images of roots from transgenic seedlings harboring YFP-tagged AtBMI1C driven by the CaMV35S promoter. Scale bar (red), 100 µm. (C) Images of petals from transgenic plants harboring YFP-tagged AtBMI1C driven by the CaMV35S promoter. Scale bar (red), 50 µm. (D) The expression pattern of AtBMI1C in seedlings and different organs was analyzed by semiquantitative RT-PCR.
Mentions: The expression pattern and subcellular localization of AtBMI1C were examined to elucidate the biological functions of the protein. To determine the subcellular localization of AtBMI1C, a reporter gene (Yellow Fluorescence Protein [YFP]) was fused to the AtBMI1C coding region under the control of the CAULIFLOWER MOSAIC VIRUS (CaMV) 35S promoter to generate stable transgenic plants carrying p35S::AtBMI1C-YFP or p35S::YFP (control). YFP signals were detected in the nucleus and cytoplasm in the roots of p35S::YFP transgenic plants (Figure 2A); in comparison, YFP signals in the roots or petals of p35S::AtBMI1C-YFP transgenic plants were detected only in the nucleus (Figure 2B and C). Thus, AtBMI1C encodes a nuclear-localized protein.

Bottom Line: No change in the H3K27me3 level in FLC chromatin was detected in an AtBMI1C-overexpressing line.Our results suggest that AtBMI1C participates in flowering time control by regulating the expression of FLC; moreover, the repression of FLC by AtBMI1C is not due to the activity of PRC2.Instead, it is likely the result of PRC1 activity, into which AtBMI1C is integrated.

View Article: PubMed Central - PubMed

Affiliation: Hebei Key Laboratory of Molecular Cell Biology, College of Biological Sciences, Hebei Normal University, Shijiazhuang, Hebei, China.

ABSTRACT
Polycomb group protein (PcG)-mediated gene silencing is emerging as an essential developmental regulatory mechanism in eukaryotic organisms. PcGs inactivate or maintain the silenced state of their target chromatin by forming complexes, including Polycomb Repressive Complex 1 (PRC1) and 2 (PRC2). Three PRC2 complexes have been identified and characterized in Arabidopsis; of these, the EMF and VRN complexes suppress flowering by catalyzing the trimethylation of lysine 27 on histone H3 of FLOWER LOCUS T (FT) and FLOWER LOCUS C (FLC). However, little is known about the role of PRC1 in regulating the floral transition, although AtRING1A, AtRING1B, AtBMI1A, and AtBMI1B are believed to regulate shoot apical meristem and embryonic development as components of PRC1. Moreover, among the five RING finger PcGs in the Arabidopsis genome, four have been characterized. Here, we report that the fifth, AtBMI1C, is a novel, ubiquitously expressed nuclear PcG protein and part of PRC1, which is evolutionarily conserved with Psc and BMI1. Overexpression of AtBMI1C caused increased H2A monoubiquitination and flowering defects in Arabidopsis. Both the suppression of FLC and activation of FT were observed in AtBMI1C-overexpressing lines, resulting in early flowering. No change in the H3K27me3 level in FLC chromatin was detected in an AtBMI1C-overexpressing line. Our results suggest that AtBMI1C participates in flowering time control by regulating the expression of FLC; moreover, the repression of FLC by AtBMI1C is not due to the activity of PRC2. Instead, it is likely the result of PRC1 activity, into which AtBMI1C is integrated.

Show MeSH
Related in: MedlinePlus