Phenotypic plasticity in plant defense across life stages: inducibility, transgenerational induction, and transgenerational priming in wild radish

Resumo

As they develop, many plants deploy shifts in anti-herbivore defense allocation due to changing costs and benefits of their defensive traits. Plant defenses are known to be primed or directly induced by herbivore damage within generations, and across generations by long-lasting epigenetic mechanisms. However, little is known about the ontogenetic trajectories of epigenetically inducible defensive traits across generations and their consequences. To help fill this knowledge gap, we conducted a multigenerational experiment to determine whether defense induction in wild radish plants was reflected in chromatin modifications (DNA methylation); we then examined ontogenetic trajectories (seedlings to reproductive plants) of current and transgenerational plasticity in anti-herbivore chemical (glucosinolates) and physical (trichomes) defenses in this species. Herbivory triggered genome methylation both in targeted plants and their offspring. Within one generation, both defenses were highly inducible at the seedling stage but only marginally or non-inducible in reproductive plants. Across generations, herbivory experienced by mother plants caused strong direct induction of physical defenses in their progeny, with effects lasting from seedling to reproductive stages. For chemical defenses, however, this transgenerational induction was evident only in adults. Transgenerational priming was observed in physical defenses both for seedlings and adult plants. Our results show that transgenerational induction and priming in response to herbivore offense differ for physical and chemical defense and change across plant life stages.