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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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Tissue-specific AtBMI1C overexpression promotes flowering in Arabidopsis.(A) Morphology of transgenic plants carrying pAP1::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 18 out of 72 independent T1 lines showed an early flowering phenotype. A few lines were chosen for the following experiments. (B) and (C) Determination of flowering time in transgenic plants containing pAP1::AtBMI1C-GFP grown under LD and SD conditions using three AtBMI1C transgenic lines as representatives. The number of rosette leaves was determined after bolting. (D) Vegetative phase transition in transgenic plants containing pAP1::AtBMI1C-GFP grown under LD conditions. Juvenile, adult, rosette, and cauline leaves were counted after flowering. Juvenile and adult leaves were distinguished based on the presence of trichomes on their abaxial surface. (E) AtBMI1C expression in transgenic lines carrying pAP1::AtBMI1C-YFP. Total RNA was extracted from leaves of pAP1::AtBMI1C-GFP and wild-type plants. AtBMI1C expression was measured by semiquantitative RT-PCR using ACTIN2/7 as an internal control. (F) Morphology of transgenic plants carrying pKNAT1::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 20 out of 108 independent T1 lines showed an early flowering phenotype. (G) Determination of flowering time in transgenic plants containing pKNAT1::AtBMI1C-GFP grown under LD conditions. The number of rosette leaves was determined after bolting. (H) Morphology of transgenic plants carrying pSUC2::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 24 out of 108 independent T1 lines showed an early flowering phenotype. (I) Determination of flowering time in transgenic plants containing pSUC2::AtBMI1C-GFP grown under LD conditions. The number of rosette leaves was determined after bolting.
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pone-0021364-g006: Tissue-specific AtBMI1C overexpression promotes flowering in Arabidopsis.(A) Morphology of transgenic plants carrying pAP1::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 18 out of 72 independent T1 lines showed an early flowering phenotype. A few lines were chosen for the following experiments. (B) and (C) Determination of flowering time in transgenic plants containing pAP1::AtBMI1C-GFP grown under LD and SD conditions using three AtBMI1C transgenic lines as representatives. The number of rosette leaves was determined after bolting. (D) Vegetative phase transition in transgenic plants containing pAP1::AtBMI1C-GFP grown under LD conditions. Juvenile, adult, rosette, and cauline leaves were counted after flowering. Juvenile and adult leaves were distinguished based on the presence of trichomes on their abaxial surface. (E) AtBMI1C expression in transgenic lines carrying pAP1::AtBMI1C-YFP. Total RNA was extracted from leaves of pAP1::AtBMI1C-GFP and wild-type plants. AtBMI1C expression was measured by semiquantitative RT-PCR using ACTIN2/7 as an internal control. (F) Morphology of transgenic plants carrying pKNAT1::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 20 out of 108 independent T1 lines showed an early flowering phenotype. (G) Determination of flowering time in transgenic plants containing pKNAT1::AtBMI1C-GFP grown under LD conditions. The number of rosette leaves was determined after bolting. (H) Morphology of transgenic plants carrying pSUC2::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 24 out of 108 independent T1 lines showed an early flowering phenotype. (I) Determination of flowering time in transgenic plants containing pSUC2::AtBMI1C-GFP grown under LD conditions. The number of rosette leaves was determined after bolting.

Mentions: pAP1::AtBMI1C-GFP was generated and introduced to wild-type plants. A total of 18 out of 72 independent transgenic lines harboring pAP1::AtBMI1C-GFP exhibited an early flowering phenotype under LD and SD conditions (Figure 6A-C and Table 2). In the mean time, the level of AtBMI1C expression in the pAP1::AtBMI1C-GFP transgenic plants was measured by semiquantitative RT-PCR. Elevated AtBMI1C expression was detected in the early flowering transgenic plants (Figure 6E), indicating that the alteration in flowering time was caused by the overexpression of AtBMI1C.


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)

Tissue-specific AtBMI1C overexpression promotes flowering in Arabidopsis.(A) Morphology of transgenic plants carrying pAP1::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 18 out of 72 independent T1 lines showed an early flowering phenotype. A few lines were chosen for the following experiments. (B) and (C) Determination of flowering time in transgenic plants containing pAP1::AtBMI1C-GFP grown under LD and SD conditions using three AtBMI1C transgenic lines as representatives. The number of rosette leaves was determined after bolting. (D) Vegetative phase transition in transgenic plants containing pAP1::AtBMI1C-GFP grown under LD conditions. Juvenile, adult, rosette, and cauline leaves were counted after flowering. Juvenile and adult leaves were distinguished based on the presence of trichomes on their abaxial surface. (E) AtBMI1C expression in transgenic lines carrying pAP1::AtBMI1C-YFP. Total RNA was extracted from leaves of pAP1::AtBMI1C-GFP and wild-type plants. AtBMI1C expression was measured by semiquantitative RT-PCR using ACTIN2/7 as an internal control. (F) Morphology of transgenic plants carrying pKNAT1::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 20 out of 108 independent T1 lines showed an early flowering phenotype. (G) Determination of flowering time in transgenic plants containing pKNAT1::AtBMI1C-GFP grown under LD conditions. The number of rosette leaves was determined after bolting. (H) Morphology of transgenic plants carrying pSUC2::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 24 out of 108 independent T1 lines showed an early flowering phenotype. (I) Determination of flowering time in transgenic plants containing pSUC2::AtBMI1C-GFP grown under LD conditions. The number of rosette leaves was determined after bolting.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3119047&req=5

pone-0021364-g006: Tissue-specific AtBMI1C overexpression promotes flowering in Arabidopsis.(A) Morphology of transgenic plants carrying pAP1::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 18 out of 72 independent T1 lines showed an early flowering phenotype. A few lines were chosen for the following experiments. (B) and (C) Determination of flowering time in transgenic plants containing pAP1::AtBMI1C-GFP grown under LD and SD conditions using three AtBMI1C transgenic lines as representatives. The number of rosette leaves was determined after bolting. (D) Vegetative phase transition in transgenic plants containing pAP1::AtBMI1C-GFP grown under LD conditions. Juvenile, adult, rosette, and cauline leaves were counted after flowering. Juvenile and adult leaves were distinguished based on the presence of trichomes on their abaxial surface. (E) AtBMI1C expression in transgenic lines carrying pAP1::AtBMI1C-YFP. Total RNA was extracted from leaves of pAP1::AtBMI1C-GFP and wild-type plants. AtBMI1C expression was measured by semiquantitative RT-PCR using ACTIN2/7 as an internal control. (F) Morphology of transgenic plants carrying pKNAT1::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 20 out of 108 independent T1 lines showed an early flowering phenotype. (G) Determination of flowering time in transgenic plants containing pKNAT1::AtBMI1C-GFP grown under LD conditions. The number of rosette leaves was determined after bolting. (H) Morphology of transgenic plants carrying pSUC2::AtBMI1C-GFP grown under LD conditions for 28 days. The plants showed an early flowering phenotype compared with wild type. A total of 24 out of 108 independent T1 lines showed an early flowering phenotype. (I) Determination of flowering time in transgenic plants containing pSUC2::AtBMI1C-GFP grown under LD conditions. The number of rosette leaves was determined after bolting.
Mentions: pAP1::AtBMI1C-GFP was generated and introduced to wild-type plants. A total of 18 out of 72 independent transgenic lines harboring pAP1::AtBMI1C-GFP exhibited an early flowering phenotype under LD and SD conditions (Figure 6A-C and Table 2). In the mean time, the level of AtBMI1C expression in the pAP1::AtBMI1C-GFP transgenic plants was measured by semiquantitative RT-PCR. Elevated AtBMI1C expression was detected in the early flowering transgenic plants (Figure 6E), indicating that the alteration in flowering time was caused by the overexpression of AtBMI1C.

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