Plant Stress Memory: Chromatin Remodeling, DNA Methylation, and Histone Marks Under Drought and Heat Stress

Acute stress responses can be mistaken for chromatin memory

Drought and heat rapidly alter transcription, histone modifications, DNA methylation, nucleosome occupancy, hormone signaling, and metabolism. Measurements collected only during active stress cannot establish whether those changes persist after the stimulus is removed. Stress memory requires persistence through recovery or an altered response during a later exposure.

Recovery is the critical experimental interval. A histone modification that rises during drought and disappears after rehydration remains part of the acute stress response. A modification that remains after stress-responsive transcription declines becomes a candidate molecular memory state. Re-exposure then tests whether the retained state accompanies faster transcription, stronger induction, altered chromatin occupancy, or improved physiological tolerance.

Plant priming studies have reported persistent DNA methylation, histone modification, small-RNA, and transcriptional changes, but causal relationships remain less common than correlations [1]. Drought-memory studies face the same problem. Multiple regulatory layers can change during repeated water deficit, while only a subset remains stable enough to influence later responses [2].

A useful stress-memory series contains untreated, first-stress, recovery, and re-stress samples. Progeny analyses require additional generations when the hypothesis concerns inherited rather than somatic memory.

Dehydration memory retains H3K4me3 after transcription declines

Repeated dehydration in Arabidopsis produces transcriptional memory at specific genes. RD29B and RAB18 show stronger transcription after previous dehydration, while RD29A and COR15A do not acquire the same response. During watered recovery, transcription from the trainable genes declines toward baseline, but H3K4me3 and Ser5-phosphorylated RNA polymerase II remain elevated [3].

The retained chromatin state disappears on a measurable timescale. Enhanced transcriptional responsiveness was maintained after several days of recovery and lost by approximately 7 days in the experimental system reported by Ding and colleagues. H3K4me3 at the memory loci followed the same temporal pattern [3].

The comparison between trainable and non-trainable loci separates ordinary stress-associated H3K4 methylation from memory-associated H3K4 methylation. Both gene classes respond during dehydration. Only the trainable genes retain elevated H3K4me3 and poised polymerase during recovery.

Locus-specific ChIP can test the same pattern in additional plant systems. The EpiQuik Plant ChIP Kit (P-2014) supports immunoprecipitation of plant chromatin for downstream PCR or sequencing analysis. A drought-memory experiment can quantify enrichment of H3K4me3, H3K27me3, a transcription factor, or another chromatin-associated protein at selected loci across untreated, stressed, recovered, and re-stressed samples.

Rice drought memory includes genes that emerge only after repeated stress

Repeated mild drought and re-watering in rice identified 6,885 memory-associated transcripts and 238 memory-associated lncRNAs distributed among 16 expression patterns [4]. Many dosage-memory genes were weakly responsive or unresponsive during the first drought treatment. Their altered expression became evident only after repeated exposure.

Candidate selection based only on the first stress response would exclude those genes. A complete treatment series captures genes with enhanced induction, attenuated induction, delayed responses, and altered recovery behavior.

ABA signaling, photosynthesis, proline metabolism, lncRNA regulation, and DNA methylation were associated with the rice memory response [4]. These pathways connect transcriptional memory with physiological adaptation rather than limiting memory to a single chromatin mark.

Whole-genome bisulfite sequencing of repeatedly drought-treated rice also identified drought-memory differentially methylated regions associated with genes and transposable elements [5]. Their genomic positions and temporal methylation patterns distinguished persistent or recurrent changes from methylation events confined to a single stress interval.

DNA methylation memory depends on genomic position and persistence

Plant DNA methylation occurs in CG, CHG, and CHH sequence contexts. Drought and osmotic stress can alter those contexts differently across gene bodies, regulatory regions, repetitive DNA, and transposable elements. Total methylated cytosine and locus-specific methylation consequently describe different biological properties.

Global 5-mC analysis measures whether total DNA methylation changes across the treatment series. The MethylFlash Global DNA Methylation (5-mC) ELISA Easy Kit (P-1030) supports global 5-mC measurement from plant DNA and can compare untreated, drought-treated, recovered, and re-stressed samples. Broad methylation shifts identified at this stage can be followed with locus-specific bisulfite analysis or genome-wide methylation mapping.

Inheritance requires evidence beyond methylation persistence in the exposed plant. Hyperosmotic stress in Arabidopsis produced methylation changes at epigenetically labile regions, but many induced states were reset in unstressed progeny. DNA glycosylase activity in the male germline restricted transmission of part of the stress-associated methylation state [6].

Somatic persistence, intergenerational transmission, and transgenerational maintenance describe different biological outcomes. A methylation change detected during recovery supports somatic memory more directly than a change detected only during stress. A methylation state detected in progeny requires controls for direct parental and germline exposure before it can be classified as inherited memory.

HSFA2 and HSFA3 establish persistent heat-responsive transcription

Arabidopsis heat memory is maintained for several days after priming. Heat shock transcription factors, chromatin regulators, histone modifications, and nucleosome remodeling participate in the maintenance phase after the acute heat-shock response subsides [7].

HSFA2 and HSFA3 form heteromeric complexes at heat-memory genes. Friedrich and colleagues showed that HSFA3 contributes to physiological heat memory, sustained memory-gene expression, and H3K4 hypermethylation. Complexes containing both HSFA2 and HSFA3 supported transcriptional memory more effectively than either factor alone [8].

H3K4 methylation at these loci is coupled to a defined transcription factor program. Measurement of total H3K4me3 abundance cannot determine whether the modification occurs at an HSFA-dependent memory locus. ChIP resolves that genomic localization.

Global histone profiling can identify which H3 modifications change across heat priming, recovery, and re-stress. The EpiQuik Histone H3 Modification Multiplex Assay Kit (P-3100) measures multiple H3 modifications in species including most plants. H3K4, H3K9, H3K27, H3K36, and acetylation states can be compared across treatment groups before selected marks are mapped at individual genes.

FORGETTER1 maintains nucleosome changes after heat stress

FORGETTER1, or FGT1, connects transcriptional heat memory with nucleosome remodeling. FGT1 associates with promoters of actively expressed genes after heat treatment and interacts with SWI/SNF and ISWI chromatin remodelers [9].

Arabidopsis fgt1 mutants show impaired maintenance of heat-induced gene expression and altered nucleosome occupancy at memory genes. MNase-based analysis at loci including HSA32, HSP22.0, HSP18.2, and HSP101 detected FGT1-dependent differences in nucleosome organization during the post-stress period [9].

Nucleosome occupancy and histone modification are independent measurements. MNase-based approaches quantify protection and positioning of nucleosomal DNA. ChIP measures enrichment of a selected histone modification or DNA-associated protein. RNA analysis measures transcriptional output. A persistent decrease in nucleosome occupancy can occur with or without a corresponding change in a specific histone modification.

Barley retains heat memory without the Arabidopsis H3K4me3 signature

Heat memory in barley retains dependence on HSFA2 and HSFA3 but differs from the Arabidopsis chromatin pattern. Pratx and colleagues reported 100% survival when barley plants were primed 2 days before severe heat and 88% survival when priming occurred 3 days earlier. Non-primed plants exposed to the severe heat treatment did not survive [10].

HvHSFA2 and HvHSFA3 mutations reduced physiological and transcriptional memory. HvHSFA2 expression increased by more than 2,000-fold immediately after acclimation in the reported experiment, while HvHSFA3 reached maximal expression later [10].

The tested barley memory genes did not acquire the H3K4me3 hypermethylation reported at Arabidopsis type II memory genes. Conserved transcription factors can therefore support comparable physiological memory through different chromatin configurations.

Crop stress-memory studies need direct measurements of candidate histone marks rather than marker sets transferred unchanged from Arabidopsis. H3K4me3, H3K27me3, H3K9 methylation, and histone acetylation can each carry different information across species, tissues, developmental stages, and stress regimens.

H3K27me3 participates in heat-associated memory through REF6

H3K27me3 regulation contributes to another Arabidopsis heat-memory pathway. Heat-induced HSFA2 activates the H3K27me3 demethylase RELATIVE OF EARLY FLOWERING 6, or REF6. REF6 promotes HSFA2 expression in return, forming a feedback loop associated with reduced H3K27me3 and transmitted heat-responsive phenotypes [11].

H3K27me3 and H3K4me3 mark different chromatin states and should not be treated as interchangeable measures of stress response. H3K4 methylation is commonly associated with transcriptionally active regions, while H3K27me3 participates in Polycomb-associated repression. Stress-dependent changes in either mark depend on the genomic locus and its regulatory proteins.

Recent analysis of plant abiotic stress regulation describes H3K4, H3K9, H3K27, and H3K36 methylation as dynamic components of environmental response, with effects determined by residue, methylation state, genomic location, and interacting regulators [12].

Assay scale determines the biological claim

Global 5-mC assays quantify total DNA methylation. Global histone assays quantify the abundance of selected histone modifications. Neither identifies the genomic regions carrying those changes.

ChIP-qPCR measures enrichment at predefined loci. ChIP-seq maps antibody-enriched chromatin across the genome.

Plant chromatin preparation, fragmentation, antibody performance, immunoprecipitation efficiency, and downstream normalization directly affect ChIP data quality. A 2026 review of histone modifications in plant priming identifies these experimental variables as major determinants of successful chromatin analysis [13].

A practical plant stress-memory workflow can begin with global methylation or histone profiling, followed by locus-specific ChIP at genes selected from transcriptomic or physiological data. Genome-wide chromatin mapping is appropriate when the hypothesis concerns regulatory programs rather than a small set of candidate genes.

EpigenTek product selector

Histone extraction in published plant studies

Published plant studies have used the EpiQuik Total Histone Extraction Kit (OP-0006) for histone-enriched fractions. Ma et al. prepared total histone-enriched fractions from Arabidopsis, tobacco, maize, and rice seedlings with OP-0006 before immunoblot analysis [14]. Published plant applications use study-specific tissue handling and downstream preparation.

Related EpigenTek chromatin profiling tools

The EpiNext CUT&LUNCH Assay Kit (P-2035) and EpiNext CUT&LUNCH-Seq Kit (P-2033) are related antibody-directed chromatin profiling tools for supported mammalian sample systems. P-2035 supports qPCR or NGS analysis of histone- or strong transcription factor-associated DNA; P-2033 incorporates sequencing library preparation.

Recovery separates persistent chromatin states from acute regulation

Arabidopsis dehydration memory retains H3K4me3 and Ser5-phosphorylated polymerase II after transcription falls during recovery. Arabidopsis heat memory retains transcriptional competence through HSFA2-HSFA3 activity and FGT1-dependent nucleosome remodeling. Barley retains HSFA2-HSFA3-dependent heat memory without the same H3K4me3 signature. Rice drought memory includes transcriptional and DNA methylation states that appear only after repeated treatment.

These studies support a specific experimental sequence. Stress identifies the acute response. Recovery tests persistence. Re-stress tests altered responsiveness. Molecular perturbation tests causality.

A chromatin modification detected only during the first treatment remains a stress-associated change. Persistence after recovery establishes a stronger memory candidate. Association with altered transcription or physiology during re-exposure strengthens the link further. Genetic or targeted perturbation of the responsible regulator provides direct evidence that the chromatin mechanism contributes to stress memory.

References

1. Harris CJ, Amtmann A, Ton J. Epigenetic processes in plant stress priming: Open questions and new approaches. Curr Opin Plant Biol. 2023;75:102432. doi:10.1016/j.pbi.2023.102432. View article
2. Rahman MM, Keya SS, Bulle M, et al. Past trauma, better future: how stress memory shapes plant adaptation to drought. Funct Plant Biol. 2025;52:FP24355. doi:10.1071/FP24355. View article
3. Ding Y, Fromm M, Avramova Z. Multiple exposures to drought 'train' transcriptional responses in Arabidopsis. Nat Commun. 2012;3:740. Published 2012 Mar 13. doi:10.1038/ncomms1732. View article
4. Li P, Yang H, Wang L, et al. Physiological and Transcriptome Analyses Reveal Short-Term Responses and Formation of Memory Under Drought Stress in Rice. Front Genet. 2019;10:55. Published 2019 Feb 8. doi:10.3389/fgene.2019.00055. View article
5. Kou, S., Gu, Q., Duan, L. et al. Genome-Wide Bisulphite Sequencing Uncovered the Contribution of DNA Methylation to Rice Short-Term Drought Memory Formation. J Plant Growth Regul 41, 2903–2917 (2022). https://doi.org/10.1007/s00344-021-10483-3. View article
6. Wibowo A, Becker C, Marconi G, et al. Hyperosmotic stress memory in Arabidopsis is mediated by distinct epigenetically labile sites in the genome and is restricted in the male germline by DNA glycosylase activity. Elife. 2016;5:e13546. Published 2016 May 31. doi:10.7554/eLife.13546. View article
7. Crawford T, Pratx L, Bäurle I. Principles and mechanisms of plant acclimation to heat stress. Nat Rev Mol Cell Biol. 2026;27(9):668-683. doi:10.1038/s41580-026-00977-x. View article
8. Friedrich T, Oberkofler V, Trindade I, et al. Heteromeric HSFA2/HSFA3 complexes drive transcriptional memory after heat stress in Arabidopsis. Nat Commun. 2021;12(1):3426. Published 2021 Jun 8. doi:10.1038/s41467-021-23786-6. View article
9. Brzezinka K, Altmann S, Czesnick H, et al. Arabidopsis FORGETTER1 mediates stress-induced chromatin memory through nucleosome remodeling. Elife. 2016;5:e17061. Published 2016 Sep 28. doi:10.7554/eLife.17061. View article
10. Pratx L, Dakhiya Y, Nissen R, et al. Conserved heat shock factors HvHSFA2 and HvHSFA3 control barley heat stress memory through diverged mechanisms. Nat Commun. 2025;16(1):10411. Published 2025 Nov 23. doi:10.1038/s41467-025-66651-6. View article
11. Liu J, Feng L, Gu X, et al. An H3K27me3 demethylase-HSFA2 regulatory loop orchestrates transgenerational thermomemory in Arabidopsis. Cell Res. 2019;29(5):379-390. doi:10.1038/s41422-019-0145-8. View article
12. Yu MH, Liao WC, Wu K. Histone methylation in plant responses to abiotic stresses. J Exp Bot. 2025;76(17):4771-4786. doi:10.1093/jxb/eraf058. View article
13. Temel A, Gören-Sağlam N. The Role of Histone Modifications in Plant Priming and Their Analysis by Chromatin Immunoprecipitation. Physiol Plant. 2026;178(3):e70915. doi:10.1111/ppl.70915. View article
14. Ma X, Chen Z, Xiao G, Huang J, Lin L, Xu Q. An evolutionarily conserved histone modification H3K37ac activates gene transcription in response to salt stress in rice. New Phytol. 2026;250(6):3516-3523. doi:10.1111/nph.70855. View article