Parental UV-B experience implicates DNA methylation in divergent offspring growth strategies under heterogeneous UV-B patterns in a clonal plant

Parental environmental experiences can induce parental effects that influence offspring phenotype, but whether the environmental heterogeneity modulates such effects remains unknown. We exposed parent ramets of the clonal plant Glechoma longituba to UV-B radiation and/or the demethylation agent 5-azacytidine, then grew their offspring under two types of heterogeneous UV-B environments: regularly alternating patches (Re) or randomly distributed patches (Ra). Parental UV-B exposure significantly enhanced offspring clonal growth, but the expression of this parental effect was pattern-dependent. In the regularly environment (Re), offspring from UV-B-treated parents increased under‑ground biomass allocation and photosynthetic capacity. In the Ra environment, they elongated secondary branch stolons and allocated more ramets to control patches. The demethylation agent 5‑Azac abolished or reversed many of these parental effects, suggesting DNA methylation may contribute to their maintenance. These results point to a potential causal contribution of DNA methylation, yet further molecular evidence is required to verify this. The heterogeneity of UV-B environments shapes the expression of clonal parental effects on offspring growth strategies. DNA methylation appears to contribute to the maintenance of such parental environmental memory. Our findings provide a potential mechanistic insight into how clonal plants may respond to complex environmental variation.