Cold stress selectively unsilences tandem repeats in heterochromatin associated with accumulation of H3K9ac

Abstract

Knobs are cytologically observable major interstitial heterochromatin present on maize nuclei, which consist of highly tandem-repetitive elements that are always silenced. Here we investigated the genome-wide change of H3K9ac, an active chromatin mark, during cold stress using chromatin immunoprecipitation sequencing (ChIP-Seq) and identified differential cold-induced H3K9ac enrichment at repetitive sequences in maize. More detailed analysis of two knob-associated tandem-repetitive sequences, 180-bp and TR-1, demonstrated that cold activated their transcription and this cold-induced transcriptional activation of repetitive sequences is selective, transient, and associated with an increase in H3K9ac and a reduction in DNA methylation and H3K9me2. Furthermore, knob sequence expression is accompanied by localized chromatin remodelling and silencing is recovered upon prolonged treatment. In addition, no evidence of copy number change and rearrangement of these repetitive elements are found in plants subjected to cold stress. These results suggest that coldmediated unsilencing of heterochromatic tandem-repeated sequences, accompanied with epigenetic regulation, might play an important role in the adaptation of plants to cold stimuli.

Drought Stress-Related Physiological Changes and Histone Modifications in Barley Primary Leaves at HSP17 Gene

“…However, control genes ACTIN and PP2A, as well as CEREBA and BM9, gained some H3K9ac under drought stress, indicating a more general stress-responsive loading with H3K9ac. Similar results have been reported, showing that heterochromatic loci may also be enriched by H3K9ac under stress conditions [59].…”

“…H3K9me2 is enriched in heterochromatin and chromocenters, and is associated with transposons without any preference along gene territory [57,63,64]. Stress-induced activation of heterochromatic loci may be accompanied with an increase in H3K9ac and a decrease in H3K9me2 [59]. As expected, CEREBA had the highest H3K9me2 levels in all conditions.…”

Low Temperature-Responsive Changes in the Anther Transcriptome’s Repeat Sequences Are Indicative of Stress Sensitivity and Pollen Sterility in Rice Strains ,

“…A change in the DNA-wrapping property of H2A.Z due to the temperature shift may induce an abnormality in the gene's expression (Wigge, 2013). A temperature shift to cold or heat can release transcriptional silencing, resulting in a genome-wide transcriptional activation in heterochromatic regions of plant genomes, which are in a constitutively inert transcriptional state under normal temperatures (Tittel-Elmer et al, 2010;Hu et al, 2012;Pecinka and Mittelsten Scheid, 2012;Oliver et al, 2013). Alternatively, the impairment of mRNA stability in Arabidopsis due to low-temperature stress may also be related to the genome-wide changes in transcriptional activity (Chiba et al, 2013).…”

Stress-induced structural changes in plant chromatin

“…Often connected with dehydration is osmotic stress or salinity, also elucidating responses at the chromatin level [reviewed in 40]. Extreme temperatures induce specific responses affecting chromatin configurations: cold stress [41][42][43] and heat stress for higher plants [36,[44][45][46] and in algae [47,48]. Light deficiency induces chromatin changes, signaled by light perception factors [22,49,50].…”