Seasonal differences in epigenetic marks and autophagy-related gene expression during natural aging of honeybee...

Honeybees (Apis mellifera L., 1758) are a valuable model for aging research due to their pronounced phenotypic plasticity, whereby genetically similar worker bees exhibit marked lifespan differences shaped by environmental and seasonal factors. We investigated age-related changes in selected epigenetic mechanisms-DNA 5-methylcytosine (5-mC), histone modifications-and autophagy-related gene expression in summer and winter worker bees originating from three independent hives. Bees were sampled as newly emerged individuals and at middle and late life stages, corresponding to two- and four-week-old summer bees and two- and four-month-old winter bees. Global DNA cytosine methylation (5-mC) levels did not vary with age in summer and winter bee generations. In contrast, DNA methyltransferases (DNMTs) exhibited pronounced tissue- and age-dependent expression patterns, including strong upregulation of DNMT isoform 3 gene (Dnmt3) in older abdominal tissues and increased expression of maintenance DNMTs, suggesting locus-specific regulatory changes. Examined histone H3 methylation marks showed no age-related variation. However, histone H3 acetylation at lysine residues 18 and 27 (H3K18ac and H3K27ac) displayed clear seasonal differences: they remained unchanged in summer bees but were elevated in winter bees, particularly at middle age. While whole-body histone acetyltransferase (HAT) activity did not differ among groups, expression of the longevity-associated deacetylase, sirtuin1 (SIRT1), declined with age in winter bees but increased in summer bees. Finally, autophagy-related genes were predominantly upregulated with age in summer bees and downregulated in winter bees. These findings demonstrate that honeybee aging can be influenced by seasonally modulated epigenetic and autophagy-related mechanisms.