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Mutations in HISTONE ACETYLTRANSFERASE1 affect sugar response and gene expression in Arabidopsis.

Heisel TJ, Li CY, Grey KM, Gibson SI - Front Plant Sci (2013)

Bottom Line: Histone acetyltransferases increase transcription of specific genes by acetylating histones associated with those genes.Mutations in HAC1 also cause reduced fertility, a moderate degree of resistance to paclobutrazol and altered transcript levels of specific genes.Involvement of a histone acetyltransferase in sugar response provides a possible mechanism whereby nutritional status could exert long-term effects on plant development and metabolism.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Biology, Microbial and Plant Genomics Institute, University of Minnesota Saint Paul, MN, USA.

ABSTRACT
Nutrient response networks are likely to have been among the first response networks to evolve, as the ability to sense and respond to the levels of available nutrients is critical for all organisms. Although several forward genetic screens have been successful in identifying components of plant sugar-response networks, many components remain to be identified. Toward this end, a reverse genetic screen was conducted in Arabidopsis thaliana to identify additional components of sugar-response networks. This screen was based on the rationale that some of the genes involved in sugar-response networks are likely to be themselves sugar regulated at the steady-state mRNA level and to encode proteins with activities commonly associated with response networks. This rationale was validated by the identification of hac1 mutants that are defective in sugar response. HAC1 encodes a histone acetyltransferase. Histone acetyltransferases increase transcription of specific genes by acetylating histones associated with those genes. Mutations in HAC1 also cause reduced fertility, a moderate degree of resistance to paclobutrazol and altered transcript levels of specific genes. Previous research has shown that hac1 mutants exhibit delayed flowering. The sugar-response and fertility defects of hac1 mutants may be partially explained by decreased expression of AtPV42a and AtPV42b, which are putative components of plant SnRK1 complexes. SnRK1 complexes have been shown to function as central regulators of plant nutrient and energy status. Involvement of a histone acetyltransferase in sugar response provides a possible mechanism whereby nutritional status could exert long-term effects on plant development and metabolism.

No MeSH data available.


HAC1 expression is repressed by sugars. Wild-type Arabidopsis seeds were surface sterilized and then incubated in the dark at 4°C for 3 days prior to being sown on nytex screens on Petri plates containing solid minimal Arabidopsis media. The seeds were incubated under continuous light at room temperature for 20 h, and then the nytex screens and seeds were transferred to Petri plates containing Arabidopsis minimal media supplemented with 0.1 M sorbitol (Sorb), Glc, or Suc. After an additional 12–13 h, seeds were harvested, followed by isolation of RNA. The RNA was then used for qRT-PCR analysis. The transcript levels of ACT7 and UBQ6 were determined and the geometric means of their Ct used to normalize transcript levels. Transcript levels are expressed as ΔΔCt. ΔΔCt = ΔCtHAC1 on sorbitol-Δ CtHAC1 on indicated media. ΔCt = CtHAC1 on indicated media-CtACT7/UBQ6 on same media. Negative ΔΔCt values indicate that HAC1 transcript levels are lower in wild-type seeds germinating on the indicated media than in wild-type seeds germinating on sorbitol. Six technical replicates were performed for each biological replicate. Error bars indicate standard deviations. HAC1 expression on sorbitol vs. Glc or Suc differed with: **p < 0.05; or ***p < 0.02, according to a Student's t-test. N = 3.
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Figure 1: HAC1 expression is repressed by sugars. Wild-type Arabidopsis seeds were surface sterilized and then incubated in the dark at 4°C for 3 days prior to being sown on nytex screens on Petri plates containing solid minimal Arabidopsis media. The seeds were incubated under continuous light at room temperature for 20 h, and then the nytex screens and seeds were transferred to Petri plates containing Arabidopsis minimal media supplemented with 0.1 M sorbitol (Sorb), Glc, or Suc. After an additional 12–13 h, seeds were harvested, followed by isolation of RNA. The RNA was then used for qRT-PCR analysis. The transcript levels of ACT7 and UBQ6 were determined and the geometric means of their Ct used to normalize transcript levels. Transcript levels are expressed as ΔΔCt. ΔΔCt = ΔCtHAC1 on sorbitol-Δ CtHAC1 on indicated media. ΔCt = CtHAC1 on indicated media-CtACT7/UBQ6 on same media. Negative ΔΔCt values indicate that HAC1 transcript levels are lower in wild-type seeds germinating on the indicated media than in wild-type seeds germinating on sorbitol. Six technical replicates were performed for each biological replicate. Error bars indicate standard deviations. HAC1 expression on sorbitol vs. Glc or Suc differed with: **p < 0.05; or ***p < 0.02, according to a Student's t-test. N = 3.

Mentions: HAC1 is predicted to encode a histone acetyltransferase that is orthologous to the p300/CREB-binding protein gene family in mammalian and yeast systems (Bordoli et al., 2001; Pandey et al., 2002). HAC1 steady-state mRNA levels are significantly lower in wild-type seeds germinating on media supplemented with Suc or Glc than in wild-type seeds germinating on media supplemented with an equi-molar concentration of sorbitol (Figure 1). To test further whether mutations in HAC1 are responsible for the sugar-response phenotype, additional lines predicted to carry T-DNA insertions in HAC1 were obtained from the Arabidopsis Biological Resource Center. Homozygous mutants were identified for a total of three independent lines that carry T-DNA inserts in HAC1. The precise locations of the T-DNA inserts in these lines were determined by PCR amplification of DNA flanking the T-DNA insertion sites, followed by DNA sequencing of the PCR products (Figure 2A). Quantitative RT-PCR was used to determine the effects of the T-DNA insertions on HAC1 transcript levels (Figure 2B). For each hac1 mutant tested, PCR primers located 5′ of the T-DNA insertion site in that hac1 line detected approximately wild-type HAC1 transcript levels. In contrast, PCR primers located 3′ of T-DNA insertion sites detected greatly reduced HAC1 transcript levels in hac1 mutants as compared to wild-type plants. These results indicate that all three hac1 mutants produce partial HAC1 transcripts that are similar in abundance to the full-length HAC1 transcripts produced by wild-type plants.


Mutations in HISTONE ACETYLTRANSFERASE1 affect sugar response and gene expression in Arabidopsis.

Heisel TJ, Li CY, Grey KM, Gibson SI - Front Plant Sci (2013)

HAC1 expression is repressed by sugars. Wild-type Arabidopsis seeds were surface sterilized and then incubated in the dark at 4°C for 3 days prior to being sown on nytex screens on Petri plates containing solid minimal Arabidopsis media. The seeds were incubated under continuous light at room temperature for 20 h, and then the nytex screens and seeds were transferred to Petri plates containing Arabidopsis minimal media supplemented with 0.1 M sorbitol (Sorb), Glc, or Suc. After an additional 12–13 h, seeds were harvested, followed by isolation of RNA. The RNA was then used for qRT-PCR analysis. The transcript levels of ACT7 and UBQ6 were determined and the geometric means of their Ct used to normalize transcript levels. Transcript levels are expressed as ΔΔCt. ΔΔCt = ΔCtHAC1 on sorbitol-Δ CtHAC1 on indicated media. ΔCt = CtHAC1 on indicated media-CtACT7/UBQ6 on same media. Negative ΔΔCt values indicate that HAC1 transcript levels are lower in wild-type seeds germinating on the indicated media than in wild-type seeds germinating on sorbitol. Six technical replicates were performed for each biological replicate. Error bars indicate standard deviations. HAC1 expression on sorbitol vs. Glc or Suc differed with: **p < 0.05; or ***p < 0.02, according to a Student's t-test. N = 3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
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Figure 1: HAC1 expression is repressed by sugars. Wild-type Arabidopsis seeds were surface sterilized and then incubated in the dark at 4°C for 3 days prior to being sown on nytex screens on Petri plates containing solid minimal Arabidopsis media. The seeds were incubated under continuous light at room temperature for 20 h, and then the nytex screens and seeds were transferred to Petri plates containing Arabidopsis minimal media supplemented with 0.1 M sorbitol (Sorb), Glc, or Suc. After an additional 12–13 h, seeds were harvested, followed by isolation of RNA. The RNA was then used for qRT-PCR analysis. The transcript levels of ACT7 and UBQ6 were determined and the geometric means of their Ct used to normalize transcript levels. Transcript levels are expressed as ΔΔCt. ΔΔCt = ΔCtHAC1 on sorbitol-Δ CtHAC1 on indicated media. ΔCt = CtHAC1 on indicated media-CtACT7/UBQ6 on same media. Negative ΔΔCt values indicate that HAC1 transcript levels are lower in wild-type seeds germinating on the indicated media than in wild-type seeds germinating on sorbitol. Six technical replicates were performed for each biological replicate. Error bars indicate standard deviations. HAC1 expression on sorbitol vs. Glc or Suc differed with: **p < 0.05; or ***p < 0.02, according to a Student's t-test. N = 3.
Mentions: HAC1 is predicted to encode a histone acetyltransferase that is orthologous to the p300/CREB-binding protein gene family in mammalian and yeast systems (Bordoli et al., 2001; Pandey et al., 2002). HAC1 steady-state mRNA levels are significantly lower in wild-type seeds germinating on media supplemented with Suc or Glc than in wild-type seeds germinating on media supplemented with an equi-molar concentration of sorbitol (Figure 1). To test further whether mutations in HAC1 are responsible for the sugar-response phenotype, additional lines predicted to carry T-DNA insertions in HAC1 were obtained from the Arabidopsis Biological Resource Center. Homozygous mutants were identified for a total of three independent lines that carry T-DNA inserts in HAC1. The precise locations of the T-DNA inserts in these lines were determined by PCR amplification of DNA flanking the T-DNA insertion sites, followed by DNA sequencing of the PCR products (Figure 2A). Quantitative RT-PCR was used to determine the effects of the T-DNA insertions on HAC1 transcript levels (Figure 2B). For each hac1 mutant tested, PCR primers located 5′ of the T-DNA insertion site in that hac1 line detected approximately wild-type HAC1 transcript levels. In contrast, PCR primers located 3′ of T-DNA insertion sites detected greatly reduced HAC1 transcript levels in hac1 mutants as compared to wild-type plants. These results indicate that all three hac1 mutants produce partial HAC1 transcripts that are similar in abundance to the full-length HAC1 transcripts produced by wild-type plants.

Bottom Line: Histone acetyltransferases increase transcription of specific genes by acetylating histones associated with those genes.Mutations in HAC1 also cause reduced fertility, a moderate degree of resistance to paclobutrazol and altered transcript levels of specific genes.Involvement of a histone acetyltransferase in sugar response provides a possible mechanism whereby nutritional status could exert long-term effects on plant development and metabolism.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Biology, Microbial and Plant Genomics Institute, University of Minnesota Saint Paul, MN, USA.

ABSTRACT
Nutrient response networks are likely to have been among the first response networks to evolve, as the ability to sense and respond to the levels of available nutrients is critical for all organisms. Although several forward genetic screens have been successful in identifying components of plant sugar-response networks, many components remain to be identified. Toward this end, a reverse genetic screen was conducted in Arabidopsis thaliana to identify additional components of sugar-response networks. This screen was based on the rationale that some of the genes involved in sugar-response networks are likely to be themselves sugar regulated at the steady-state mRNA level and to encode proteins with activities commonly associated with response networks. This rationale was validated by the identification of hac1 mutants that are defective in sugar response. HAC1 encodes a histone acetyltransferase. Histone acetyltransferases increase transcription of specific genes by acetylating histones associated with those genes. Mutations in HAC1 also cause reduced fertility, a moderate degree of resistance to paclobutrazol and altered transcript levels of specific genes. Previous research has shown that hac1 mutants exhibit delayed flowering. The sugar-response and fertility defects of hac1 mutants may be partially explained by decreased expression of AtPV42a and AtPV42b, which are putative components of plant SnRK1 complexes. SnRK1 complexes have been shown to function as central regulators of plant nutrient and energy status. Involvement of a histone acetyltransferase in sugar response provides a possible mechanism whereby nutritional status could exert long-term effects on plant development and metabolism.

No MeSH data available.