Core promoter acetylation is not required for high transcription from the phosphoenolpyruvate carboxylase promoter in maize

Abstract

BackgroundAcetylation of promoter nucleosomes is tightly correlated and mechanistically linked to gene activity. However, transcription is not necessary for promoter acetylation. It seems, therefore, that external and endogenous stimuli control histone acetylation and by this contribute to gene regulation. Photosynthetic genes in plants are excellent models with which to study the connection between stimuli and chromatin modifications because these genes are strongly expressed and regulated by multiple stimuli that are easily manipulated. We have previously shown that acetylation of specific histone lysine residues on the photosynthetic phosphoenolpyruvate carboxylase (Pepc) promoter in maize is controlled by light and is independent of other stimuli or gene activity. Acetylation of upstream promoter regions responds to a set of other stimuli which include the nutrient availability of the plant. Here, we have extended these studies by analysing histone acetylation during the diurnal and circadian rhythm of the plant.ResultsWe show that histone acetylation of individual lysine residues is removed from the core promoter before the end of the illumination period which is an indication that light is not the only factor influencing core promoter acetylation. Deacetylation is accompanied by a decrease in gene activity. Pharmacological inhibition of histone deacetylation is not sufficient to prevent transcriptional repression, indicating that deacetylation is not controlling diurnal gene regulation. Variation of the Pepc promoter activity during the day is controlled by the circadian oscillator as it is maintained under constant illumination for at least 3 days. During this period, light-induced changes in histone acetylation are completely removed from the core promoter, although the light stimulus is continuously applied. However, acetylation of most sites on upstream promoter elements follows the circadian rhythm.ConclusionOur results suggest a central role of upstream promoter acetylation in the quantitative regulation of gene expression in this model gene. Induced core promoter acetylation is dispensable for the highest gene expression in the diurnal and circadian rhythm.

Chromatin modification acts as a memory for systemic acquired resistance in the plant stress response

“…Not many examples exist that correlate histone modifications with a transcriptionally poised state. In maize, the tissue specificity of photosynthetic genes is controlled by H3K4me3 and is established independently of transcriptional activation (Offermann et al , 2006; Danker et al , 2008; Horst et al , 2009). Similar stimulus‐dependent control of histone modifications was described for the vernalization response in Arabidopsis (He & Amasino, 2005) and the hormonal regulation of the beta‐phaseolin promoter in beans (Ng et al , 2006).…”

Photosynthetic Genes and Genes Associated with the C4 Trait in Maize Are Characterized by a Unique Class of Highly Regulated Histone Acetylation Peaks on Upstream Promoters

“…Harvested leaf sections from 10 plants per biological replicate were pooled, and chromatin was cross linked as described (Horst et al, 2009). Chromatin isolation and immunoprecipitation were performed as described , with the exception that protein A agarose was not blocked with salmon sperm DNA.…”

“…We defined specific modifications that were associated with light regulation (Offermann et al, 2006), differentiation of M and BS cells , circadian regulation (Horst et al, 2009), or metabolic regulation of C4 genes . This code was, at least in part, conserved in other C4 grasses Horst et al, 2013).…”

A Common Histone Modification Code on C4 Genes in Maize and Its Conservation in Sorghum and Setaria italica

“…As described previously by Horst et al (2009), 6 g of leaves from 10-to 12-dold maize seedlings was harvested and cross linked. For sorghum and S. italica, 4 g of leaves from 14-to 16-d-old seedlings was harvested and vacuum infiltrated with 1% (v/v) formaldehyde instead of 3% (v/v) for maize.…”