Abstract
Background: Transgenerational epigenetic inheritance (TEI) in Caenorhabditis elegans is mediated by small RNAs and histone modifications, yet the stability and phenotypic consequences of stress-induced histone marks across multiple generations remain poorly characterized. Here we investigated whether acute heat stress triggers heritable histone methylation changes that influence fitness-related traits.Methods: L4-stage wild-type C. elegans were exposed to a mild heat shock (30°C, 2 h). Chromatin immunoprecipitation followed by quantitative PCR (ChIP‑qPCR) was performed on pooled embryos from the parental (F₀) and three subsequent generations (F₁–F₃) to measure enrichment of H3K9me3 and H3K4me3 at target loci. Parallel cohorts were assessed for lifespan and brood size. Data were analysed using ANOVA and mixed-effects regression.Results: H3K9me3 levels at repetitive loci were significantly elevated in F₁ (1.6‑fold, p Conclusions: Acute heat stress induces histone H3K9me3 modifications that are inherited for at least two generations, suggesting a mechanism of transient epigenetic memory. The lack of persistent phenotypic changes implies that such marks may facilitate adaptive plasticity without permanently altering fitness. Our findings support a model in which stress‑induced histone modifications are gradually reset through germline reprogramming, possibly involving small‑RNA pathways.