Initial studies showed that, depending on the plant species, environmentally stressed maternal individuals may either increase or decrease the quantity of nutritive tissues allocated to developing seeds ( Haig and Westoby, 1988 Schmitt et al., 1992 Sultan, 1996 Donohue and Schmitt, 1998 Fenner and Thompson, 2005). A great deal remains to be determined about both the nature of these inherited developmental effects and their transmission mechanisms. This information includes more than genes alone, because organisms also inherit environmentally induced developmental factors from their parents, such as altered provisioning of resources to the embryo and epigenetic modifications of genetic material (reviewed by Roach and Wulff, 1987 Herman and Sultan, 2011 Bonduriansky et al., 2012 English et al., 2015). These results contribute to the increasing body of evidence that DNA methylation can mediate transgenerational environmental effects, and show that such effects may contribute to nuanced developmental interactions between parental and immediate environments.ДЄ fundamental question in understanding phenotypic variation is how organisms integrate environmental cues with inherited biological information to guide development. Partial demethylation of progeny DNA had no phenotypic effect on offspring of shaded parents, but caused offspring of sun-grown parents to develop as if their parents had been shaded, with larger leaves and greater total canopy area and biomass. To test for a role of DNA methylation, we exposed replicate offspring of isogenic shaded and fully insolated parents to either the demethylating agent zebularine or to control conditions during germination, then raised them in simulated growth chamber shade. Based on both regression and covariate analysis, inherited effects of parental shade were not mediated by changes to seed provisioning. These shade-adaptive effects of parental shade were pronounced and highly significant for seedlings growing in shade, but slight and generally non-significant for seedlings growing in sun. Compared to the offspring of sun-grown parents, the offspring of shade-grown parents produced leaves with greater mean and specific leaf area, and had higher total leaf area and biomass. We grew replicate parents of five highly inbred Polygonum persicaria genotypes in glasshouse shade versus sun and, in a fully factorial design, measured ecologically important traits of their isogenic seedling offspring in both environments. We show that parental light environment (shade versus sun) resulted in context-dependent effects on seedling development in a common annual plant, and that these effects were mediated by DNA methylation. Such context-dependent transgenerational plasticity suggests a mechanism of environmental inheritance that can precisely interact with immediate response pathways, such as epigenetic modification.

However, because development of individual organisms is guided by both inherited and immediate environmental cues, parental conditions may have different effects depending on progeny environment. Such inherited environmental effects may alter offspring phenotypes in a consistent way, for instance when resource-deprived parents produce low quality offspring due to reduced maternal provisioning. Parental environment influences progeny development in numerous plant and animal systems. Biology Department, Wesleyan University, Middletown, CT, United States.

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