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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

Effects of DNA methylation inhibitor 5-aza-2′-deoxycytidine (5-azadC) on the growth and development of WTLUC,hsi2-2LUCandhsi2-4LUCseedlings. Seeds were germinated vertically on media plates containing various concentrations of 5-azadC and pictures were taken 7 days after germination. A. Morphology of seedlings. B. Measurements of hypocotyl and root growths. Hypocotyl and root lengths were measured using ImageJ software. Data represent mean values (±SD) from 10 seedlings. The experiments were repeated with two technical replicates. Letters indicate significant differences between WTLUC and hsi2-2LUC or hsi2-4LUC at each time point (a = p< 0.005, b = p< 0.0001).
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Fig4: Effects of DNA methylation inhibitor 5-aza-2′-deoxycytidine (5-azadC) on the growth and development of WTLUC,hsi2-2LUCandhsi2-4LUCseedlings. Seeds were germinated vertically on media plates containing various concentrations of 5-azadC and pictures were taken 7 days after germination. A. Morphology of seedlings. B. Measurements of hypocotyl and root growths. Hypocotyl and root lengths were measured using ImageJ software. Data represent mean values (±SD) from 10 seedlings. The experiments were repeated with two technical replicates. Letters indicate significant differences between WTLUC and hsi2-2LUC or hsi2-4LUC at each time point (a = p< 0.005, b = p< 0.0001).

Mentions: We noticed that the growth and development of WTLUC seedlings on plates that contained 5 μM/mL 5-azadC was more strongly inhibited than hsi2-2LUC and hsi2-4LUC mutant seedlings (Figure 4A). To further characterize the effects of 5-azadC on hypocotyl and root growth, WTLUC, hsi2-2LUC and hsi2-4LUC seeds were germinated on media containing 0, 1, 5, 10 and 20 μM 5-azadC. After 7 days of incubation on 5-azadC-containing media, all seedlings showed dose-dependent inhibition of growth and development. However, the most severe effects were seen with WTLUC seedlings whereas the growth of hsi2-2LUC and hsi2-4LUC mutant seedlings was less inhibited (Figure 4A). While WTLUC seeds germinated when incubated on media containing 20 μM 5-azadC, subsequent root growth and cotyledon development was almost completely abrogated while both and hsi2-4LUC and hsi2-2LUC mutant seedlings continued to grow and develop, albeit slowly, under these conditions (Figure 4A and B). Comparative measurements of hypocotyl and root growth indicated that hsi2-2LUC and hsi2-4LUC mutant seedlings were about one half as sensitive to 5-azadC-dependent inhibition as WTLUC seedlings at 5, 10 and 20 μM 5-azadC treatments (Figure 4B). These data indicate that, although 5-azadC does not affect the HSI2-dependent suppression of luciferase expression in WTLUC plants, HSI2 does affect sensitivity to 5-azadC-dependent inhibition of seedling development.Figure 4


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)

Effects of DNA methylation inhibitor 5-aza-2′-deoxycytidine (5-azadC) on the growth and development of WTLUC,hsi2-2LUCandhsi2-4LUCseedlings. Seeds were germinated vertically on media plates containing various concentrations of 5-azadC and pictures were taken 7 days after germination. A. Morphology of seedlings. B. Measurements of hypocotyl and root growths. Hypocotyl and root lengths were measured using ImageJ software. Data represent mean values (±SD) from 10 seedlings. The experiments were repeated with two technical replicates. Letters indicate significant differences between WTLUC and hsi2-2LUC or hsi2-4LUC at each time point (a = p< 0.005, b = p< 0.0001).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig4: Effects of DNA methylation inhibitor 5-aza-2′-deoxycytidine (5-azadC) on the growth and development of WTLUC,hsi2-2LUCandhsi2-4LUCseedlings. Seeds were germinated vertically on media plates containing various concentrations of 5-azadC and pictures were taken 7 days after germination. A. Morphology of seedlings. B. Measurements of hypocotyl and root growths. Hypocotyl and root lengths were measured using ImageJ software. Data represent mean values (±SD) from 10 seedlings. The experiments were repeated with two technical replicates. Letters indicate significant differences between WTLUC and hsi2-2LUC or hsi2-4LUC at each time point (a = p< 0.005, b = p< 0.0001).
Mentions: We noticed that the growth and development of WTLUC seedlings on plates that contained 5 μM/mL 5-azadC was more strongly inhibited than hsi2-2LUC and hsi2-4LUC mutant seedlings (Figure 4A). To further characterize the effects of 5-azadC on hypocotyl and root growth, WTLUC, hsi2-2LUC and hsi2-4LUC seeds were germinated on media containing 0, 1, 5, 10 and 20 μM 5-azadC. After 7 days of incubation on 5-azadC-containing media, all seedlings showed dose-dependent inhibition of growth and development. However, the most severe effects were seen with WTLUC seedlings whereas the growth of hsi2-2LUC and hsi2-4LUC mutant seedlings was less inhibited (Figure 4A). While WTLUC seeds germinated when incubated on media containing 20 μM 5-azadC, subsequent root growth and cotyledon development was almost completely abrogated while both and hsi2-4LUC and hsi2-2LUC mutant seedlings continued to grow and develop, albeit slowly, under these conditions (Figure 4A and B). Comparative measurements of hypocotyl and root growth indicated that hsi2-2LUC and hsi2-4LUC mutant seedlings were about one half as sensitive to 5-azadC-dependent inhibition as WTLUC seedlings at 5, 10 and 20 μM 5-azadC treatments (Figure 4B). These data indicate that, although 5-azadC does not affect the HSI2-dependent suppression of luciferase expression in WTLUC plants, HSI2 does affect sensitivity to 5-azadC-dependent inhibition of seedling development.Figure 4

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