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HSI2/VAL1 PHD-like domain promotes H3K27 trimethylation to repress the expression of seed maturation genes and complex transgenes in Arabidopsis seedlings.

Veerappan V, Chen N, Reichert AI, Allen RD - BMC Plant Biol. (2014)

Bottom Line: Expression of LUC and Neomycin Phosphotransferase II transgenes is associated with dynamic changes in H3K27me3 levels, and the activation marks H3K4me3 and H3K36me3 but does not appear to involve repressive H3K9me2 marks, DNA methylation or histone deacetylation.HSI2 is also required for the repression of a subset of regulatory and structural seed maturation genes in vegetative tissues and H3K27me3 marks associated with most of these genes are also HSI2-dependent.These data implicate HSI2 PHD-like domain in the regulation of gene expression involving histone modifications and DNA methylation-mediated epigenetic mechanisms.

View Article: PubMed Central - PubMed

ABSTRACT

Background: The novel mutant allele hsi2-4 was isolated in a genetic screen to identify Arabidopsis mutants with constitutively elevated expression of a glutathione S-transferase F8::luciferase (GSTF8::LUC) reporter gene in Arabidopsis. The hsi2-4 mutant harbors a point mutation that affects the plant homeodomain (PHD)-like domain in HIGH-LEVEL EXPRESSION OF SUGAR-INDUCIBLE GENE2 (HSI2)/VIVIPAROUS1/ABI3-LIKE1 (VAL1). In hsi2-4 seedlings, expression of this LUC transgene and certain endogenous seed-maturation genes is constitutively enhanced. The parental reporter line (WT LUC ) that was used for mutagenesis harbors two independent transgene loci, Kan R and Kan S . Both loci express luciferase whereas only the Kan R locus confers resistance to kanamycin.

Results: Here we show that both transgene loci harbor multiple tandem insertions at single sites. Luciferase expression from these sites is regulated by the HSI2 PHD-like domain, which is required for the deposition of repressive histone methylation marks (H3K27me3) at both Kan R and Kan S loci. Expression of LUC and Neomycin Phosphotransferase II transgenes is associated with dynamic changes in H3K27me3 levels, and the activation marks H3K4me3 and H3K36me3 but does not appear to involve repressive H3K9me2 marks, DNA methylation or histone deacetylation. However, hsi2-2 and hsi2-4 mutants are partially resistant to growth inhibition associated with exposure to the DNA methylation inhibitor 5-aza-2'-deoxycytidine. HSI2 is also required for the repression of a subset of regulatory and structural seed maturation genes in vegetative tissues and H3K27me3 marks associated with most of these genes are also HSI2-dependent.

Conclusions: These data implicate HSI2 PHD-like domain in the regulation of gene expression involving histone modifications and DNA methylation-mediated epigenetic mechanisms.

No MeSH data available.


Related in: MedlinePlus

Genomic structure ofGSTF8::LUCtransgene and luminescence imaging of WTLUCandhsi2-4mutant seedlings harboring eitherKanRorKanStransgene locus or both. A. GSTF8::LUC transgene contain neomycin phosphotransferase (NPTII) coding sequences under the control of nopaline synthase (NOS) promoter and a modified luciferase (LUC+) coding sequences from firefly driven by glutathione S-transferase F8 (GSTF8) promoter conferring kanamycin resistance and luminescence expression respectively in plants. The 3′ ends of both NPTII and LUC+ coding sequences include NOS terminator sequences for transcriptional termination. B. Plants harboring either KanR or KanS transgene locus alone in the wild-type or in hsi2-4 mutant background were obtained by crossing of either WTLUC or hsi2-4LUC into Columbia-0 wild-type and homozygous lines were identified in F2 and F3 generations. Five days old seedlings of various genotypes grown on Murashige and Skoog media plates were imaged using cooled CCD camera after spraying with the substrate luciferin. Pseudocolor image indicates luminescence intensity from lowest (blue) to highest (white).
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Fig1: Genomic structure ofGSTF8::LUCtransgene and luminescence imaging of WTLUCandhsi2-4mutant seedlings harboring eitherKanRorKanStransgene locus or both. A. GSTF8::LUC transgene contain neomycin phosphotransferase (NPTII) coding sequences under the control of nopaline synthase (NOS) promoter and a modified luciferase (LUC+) coding sequences from firefly driven by glutathione S-transferase F8 (GSTF8) promoter conferring kanamycin resistance and luminescence expression respectively in plants. The 3′ ends of both NPTII and LUC+ coding sequences include NOS terminator sequences for transcriptional termination. B. Plants harboring either KanR or KanS transgene locus alone in the wild-type or in hsi2-4 mutant background were obtained by crossing of either WTLUC or hsi2-4LUC into Columbia-0 wild-type and homozygous lines were identified in F2 and F3 generations. Five days old seedlings of various genotypes grown on Murashige and Skoog media plates were imaged using cooled CCD camera after spraying with the substrate luciferin. Pseudocolor image indicates luminescence intensity from lowest (blue) to highest (white).

Mentions: The GSTF8::LUC reporter construct contains a GSTF8 promoter sequence that controls the transcription of a luciferase expression cassette, along with an NPTII gene under control of the nopaline synthase promoter and terminator sequences, which confers kanamycin resistance in plants (Figure 1A). The parental WTLUC reporter line harbors two independent transgene insertion sites, KanR and KanS. The KanR locus was mapped to chromosome IV, while the KanS locus is located on chromosome V (Table 1) [14]. Active luciferase is expressed by both KanR and KanS loci, conferring a luminescent phenotype; however, only the KanR locus expresses NPTII; thus, plants that harbor only the KanR locus are resistant to kanamycin, while KanS plants are sensitive to this antibiotic.Figure 1


HSI2/VAL1 PHD-like domain promotes H3K27 trimethylation to repress the expression of seed maturation genes and complex transgenes in Arabidopsis seedlings.

Veerappan V, Chen N, Reichert AI, Allen RD - BMC Plant Biol. (2014)

Genomic structure ofGSTF8::LUCtransgene and luminescence imaging of WTLUCandhsi2-4mutant seedlings harboring eitherKanRorKanStransgene locus or both. A. GSTF8::LUC transgene contain neomycin phosphotransferase (NPTII) coding sequences under the control of nopaline synthase (NOS) promoter and a modified luciferase (LUC+) coding sequences from firefly driven by glutathione S-transferase F8 (GSTF8) promoter conferring kanamycin resistance and luminescence expression respectively in plants. The 3′ ends of both NPTII and LUC+ coding sequences include NOS terminator sequences for transcriptional termination. B. Plants harboring either KanR or KanS transgene locus alone in the wild-type or in hsi2-4 mutant background were obtained by crossing of either WTLUC or hsi2-4LUC into Columbia-0 wild-type and homozygous lines were identified in F2 and F3 generations. Five days old seedlings of various genotypes grown on Murashige and Skoog media plates were imaged using cooled CCD camera after spraying with the substrate luciferin. Pseudocolor image indicates luminescence intensity from lowest (blue) to highest (white).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4232687&req=5

Fig1: Genomic structure ofGSTF8::LUCtransgene and luminescence imaging of WTLUCandhsi2-4mutant seedlings harboring eitherKanRorKanStransgene locus or both. A. GSTF8::LUC transgene contain neomycin phosphotransferase (NPTII) coding sequences under the control of nopaline synthase (NOS) promoter and a modified luciferase (LUC+) coding sequences from firefly driven by glutathione S-transferase F8 (GSTF8) promoter conferring kanamycin resistance and luminescence expression respectively in plants. The 3′ ends of both NPTII and LUC+ coding sequences include NOS terminator sequences for transcriptional termination. B. Plants harboring either KanR or KanS transgene locus alone in the wild-type or in hsi2-4 mutant background were obtained by crossing of either WTLUC or hsi2-4LUC into Columbia-0 wild-type and homozygous lines were identified in F2 and F3 generations. Five days old seedlings of various genotypes grown on Murashige and Skoog media plates were imaged using cooled CCD camera after spraying with the substrate luciferin. Pseudocolor image indicates luminescence intensity from lowest (blue) to highest (white).
Mentions: The GSTF8::LUC reporter construct contains a GSTF8 promoter sequence that controls the transcription of a luciferase expression cassette, along with an NPTII gene under control of the nopaline synthase promoter and terminator sequences, which confers kanamycin resistance in plants (Figure 1A). The parental WTLUC reporter line harbors two independent transgene insertion sites, KanR and KanS. The KanR locus was mapped to chromosome IV, while the KanS locus is located on chromosome V (Table 1) [14]. Active luciferase is expressed by both KanR and KanS loci, conferring a luminescent phenotype; however, only the KanR locus expresses NPTII; thus, plants that harbor only the KanR locus are resistant to kanamycin, while KanS plants are sensitive to this antibiotic.Figure 1

Bottom Line: Expression of LUC and Neomycin Phosphotransferase II transgenes is associated with dynamic changes in H3K27me3 levels, and the activation marks H3K4me3 and H3K36me3 but does not appear to involve repressive H3K9me2 marks, DNA methylation or histone deacetylation.HSI2 is also required for the repression of a subset of regulatory and structural seed maturation genes in vegetative tissues and H3K27me3 marks associated with most of these genes are also HSI2-dependent.These data implicate HSI2 PHD-like domain in the regulation of gene expression involving histone modifications and DNA methylation-mediated epigenetic mechanisms.

View Article: PubMed Central - PubMed

ABSTRACT

Background: The novel mutant allele hsi2-4 was isolated in a genetic screen to identify Arabidopsis mutants with constitutively elevated expression of a glutathione S-transferase F8::luciferase (GSTF8::LUC) reporter gene in Arabidopsis. The hsi2-4 mutant harbors a point mutation that affects the plant homeodomain (PHD)-like domain in HIGH-LEVEL EXPRESSION OF SUGAR-INDUCIBLE GENE2 (HSI2)/VIVIPAROUS1/ABI3-LIKE1 (VAL1). In hsi2-4 seedlings, expression of this LUC transgene and certain endogenous seed-maturation genes is constitutively enhanced. The parental reporter line (WT LUC ) that was used for mutagenesis harbors two independent transgene loci, Kan R and Kan S . Both loci express luciferase whereas only the Kan R locus confers resistance to kanamycin.

Results: Here we show that both transgene loci harbor multiple tandem insertions at single sites. Luciferase expression from these sites is regulated by the HSI2 PHD-like domain, which is required for the deposition of repressive histone methylation marks (H3K27me3) at both Kan R and Kan S loci. Expression of LUC and Neomycin Phosphotransferase II transgenes is associated with dynamic changes in H3K27me3 levels, and the activation marks H3K4me3 and H3K36me3 but does not appear to involve repressive H3K9me2 marks, DNA methylation or histone deacetylation. However, hsi2-2 and hsi2-4 mutants are partially resistant to growth inhibition associated with exposure to the DNA methylation inhibitor 5-aza-2'-deoxycytidine. HSI2 is also required for the repression of a subset of regulatory and structural seed maturation genes in vegetative tissues and H3K27me3 marks associated with most of these genes are also HSI2-dependent.

Conclusions: These data implicate HSI2 PHD-like domain in the regulation of gene expression involving histone modifications and DNA methylation-mediated epigenetic mechanisms.

No MeSH data available.


Related in: MedlinePlus