Abstract
Acclimation to high temperature increases plants’ tolerance of subsequent lethal high temperatures. Although epigenetic regulation of plant gene expression is well studied, how plants maintain a memory of environmental changes over time remains unclear. Here, we show that JUMONJI (JMJ) proteins, demethylases involved in histone H3 lysine 27 trimethylation (H3K27me3), are necessary for Arabidopsis thaliana heat acclimation. Acclimation induces sustained H3K27me3 demethylation at HEAT SHOCK PROTEIN22 (HSP22) and HSP17.6C loci by JMJs, poising the HSP genes for subsequent activation. Upon sensing heat after a 3-day interval, JMJs directly reactivate these HSP genes. Finally, jmj mutants fail to maintain heat memory under fluctuating field temperature conditions. Our findings of an epigenetic memory mechanism involving histone demethylases may have implications for environmental adaptation of field plants.
Highlights
Acclimation to high temperature increases plants’ tolerance of subsequent lethal high temperatures
To gain insight into the role of histone modification enzymes in the maintenance of heat memory, we focused on a group of the Jumonji-C-domain-containing proteins (JMJs) involved in H3K27me[3] removal
Among the 21 JMJ proteins in A. thaliana, five reportedly possess H3K27me[3] demethylation activity: JMJ30, JMJ32, JMJ11/EARLY FLOWERING 6 (ELF6), REF6, and JMJ134–8. To see whether these proteins are involved in heat memory, we investigated the heat responses of a series of jmj mutants (Fig. 1a–i)
Summary
Acclimation to high temperature increases plants’ tolerance of subsequent lethal high temperatures. Epigenetic regulation of plant gene expression is well studied, how plants maintain a memory of environmental changes over time remains unclear. We show that JUMONJI (JMJ) proteins, demethylases involved in histone H3 lysine 27 trimethylation (H3K27me3), are necessary for Arabidopsis thaliana heat acclimation. We demonstrated that JMJ proteins maintain low levels of repressive histone marks on small chaperone-encoding HSPs13,14 that function as memory genes. Using inducible JMJs and mutants of small HSPs, we demonstrated that the underlying basis of heat memory is at least partially mediated by the sustained demethylation of H3K27me[3] on small HSPs. We developed a mathematical stochastic model for this histone modification-based transcriptional memory that successfully predicts expression levels of HSPs. our data under recapitulated fluctuating temperature conditions indicates that JMJ-mediated sustained H3K27me[3] demethylation on small HSPs controls recurring heat memory
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