Title : Epigenetic regulation of thermotolerance by heat-activated JMJ29 in Arabidopsis
Abstract:
Heat stress severely disrupts cellular homeostasis, protein stability, and plant growth. To cope with elevated temperatures, plants rapidly activate heat-responsive genes and remodel chromatin to enable dynamic transcriptional reprogramming, a process tightly regulated by epigenetic mechanisms. Among epigenetic modifications, histone methylation plays a crucial role in transcriptional regulation and is dynamically controlled by histone methyltransferases and demethylases. In Arabidopsis thaliana, more than 21 Jumonji C (JmjC) domain–containing histone demethylases are classified into five subgroups. JMJ29, a member of the JHDM2/KDM3 subgroup, specifically demethylates the repressive H3K9me2 mark; however, its role in heat stress responses has remained unclear. In this study, we investigated the function of JMJ29 in plant thermal tolerance. Exposure of 21-day-old Arabidopsis seedlings to 38 °C for three days resulted in strong induction of JMJ29 expression. Functional analyses using JMJ29 overexpression lines, amiRNA knockdown lines, complemented lines, and a T-DNA insertion mutant revealed that elevated JMJ29 levels enhance heat tolerance, whereas loss of JMJ29 function increases heat sensitivity. To further elucidate its regulatory role, we performed global transcriptome sequencing of wild-type (Col-0), jmj29 mutant, and JMJ29 overexpression plants. Transcriptomic analyses showed that JMJ29 regulates a broad set of heat-responsive genes. Notably, auxin biosynthesis-related genes were significantly upregulated in JMJ29 overexpression lines, suggesting a link between epigenetic regulation, hormonal signaling, and heat stress adaptation. Collectively, our findings establish JMJ29 as a key epigenetic regulator of gene expression during heat stress in plants.
