GEOapplication/xmlftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE326nnn/GSE326561/primaryOK200TranscriptomicsCyanidioschyzon merolae Cyanidioschyzon merolae strain 10DExpression profiling by high throughput sequencinghttps://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE326561GEOGSEfalseRemembering heat: How the unicellular alga Cyanidioschyzon merolae establishes a molecular stress memory that boosts its thermotoleranceA powerful way to enhance heat tolerance is by establishing a stress memory through exposure to a heat stress that is strong enough to induce a molecular stress response without causing irreversible damage, followed by a recovery phase. While this has been extensively studied in multicellular organisms, we demonstrate that heat stress memory is also present in the unicellular red alga Cyanidioschyzon merolae. We show that, similarly to more complex organisms, thermomemory in this alga is underpinned by transcriptomic reprogramming, with the chloroplast emerging as the main site of gene trainability. Additionally, we find a conserved small heat shock protein (sHSP)-encoding locus in the nuclear genome to be heat-trainable, likely by histone depletion and modification through the repressive mark H3K27me3. We show that of C. merolae’s two sHSPs, only CmsHSP2 is necessary for proper HS memory establishment, and that the two sHSPs localize to different cellular compartments during heat stress. Finally, comparative RNA-Sequencing of an Enhancer of zeste mutant reveals a role for the H3K27me3-transferase in adapting the transcriptome to recurring heat exposures, beyond regulating the trainable sHSP locus.2026/04/05GSE326561GSM9634472GSM9634473GSM9634474GSM9634475GSM9634476GSM9634477GSM9634478GSM9634479GSM9634490GSM9634491GSM9634470GSM9634492GSM9634493GSM9634471GSM9634469GSM9634483GSM9634484GSM9634485GSM9634464GSM9634486GSM9634487GSM9634465GSM9634488GSM9634466GSM9634467GSM9634489GSM9634468GSM9634480GSM9634481GSM963448235234326561Cyanidioschyzon merolae Cyanidioschyzon merolae strain 10D