When does it pay off to prime for defense? A modeling analysis

Abstract

Summary Plants can prepare for future herbivore attack through a process called priming. Primed plants respond more strongly and/or faster to insect attack succeeding the priming event than nonprimed plants, while the energetic costs of priming are relatively low.To better understand the evolution of priming, we developed a simulation model, partly parameterized for Brassica nigra plants, to explore how the fitness benefits of priming change when plants are grown in different biotic environments.Model simulations showed that herbivore dynamics (arrival probability, arrival time, and feeding rate) affect the optimal duration, the optimal investment and the fitness benefits of priming. Competition for light increases the indirect costs of priming, but may also result in a larger payoff when the nonprimed plant experiences substantial leaf losses.This modeling approach identified some important knowledge gaps: herbivore arrival rates on individual plants are rarely reported but they shape the optimal duration of priming, and it would pay off if the likelihood, severity and timing of the attack could be discerned from the priming cue, but it is unknown if plants can do so. In addition, the model generated some testable predictions, for example that the sensitivity to the priming cue decreases with plant age.

Good neighbors make good defenses: associational refuges reduce defense investment in African savanna plants

“…This result is consistent with previous studies of induced-response priming in other systems (Frost et al 2008). Priming is thus a likely mechanism by which unassociated (and, analogously, unfenced) plants produced such rapid responses, and it provides a plausible explanation for the observed intraspecific variation in the magnitude and speed of induced resistance to browsing in B. trispinosa (Frost et al 2008, Douma et al 2017. Priming is thus a likely mechanism by which unassociated (and, analogously, unfenced) plants produced such rapid responses, and it provides a plausible explanation for the observed intraspecific variation in the magnitude and speed of induced resistance to browsing in B. trispinosa (Frost et al 2008, Douma et al 2017.…”

“…For example, while the intensity and frequency of herbivory is typically low within refuges, herbivory pressure can be significantly more severe and variable in the open habitat immediately outside refuges (e.g., Hay 1986, Coverdale et al 2016. Moreover, associational refuges may further affect the speed and/or magnitude of induced responses via defense "priming", the synthesis and storage of precursors necessary for defense production (Douma et al 2017). Moreover, associational refuges may further affect the speed and/or magnitude of induced responses via defense "priming", the synthesis and storage of precursors necessary for defense production (Douma et al 2017).…”

“…Inducible resistance may thus be favored in landscapes with discrete refuge patches, because mismatches between defense phenotype and herbivory risk can have deleterious effects on plant fitness (Orrock et al 2015). Moreover, associational refuges may further affect the speed and/or magnitude of induced responses via defense "priming", the synthesis and storage of precursors necessary for defense production (Douma et al 2017). Primed plants often respond more strongly and/ or rapidly to subsequent herbivore attack, and interactions with neighbors can cause plants to enter a primed state (Frost et al 2008, Karban et al 2014, Kim 2017.…”

The Asian corn borer Ostrinia furnacalis feeding increases the direct and indirect defence of mid‐whorl stage commercial maize in the field

“…In this case, we speculate that Jingke968 may prepare for O. furnacalis attack before it actually experiences O. furnacalis , a phenomenon known as defence priming (Group et al ., ; Martinez‐Medina et al ., ). Plants with primed defence can respond quickly, strongly and over long periods to biotic and abiotic stress (Douma et al ., ; Mauch‐mani et al ., ), which can reduce the damage inflicted over the time it takes to produce induced defences (Frost et al ., ). Although we could not exclude the external factors from field conditions including GLVs from other plants, insects body odour and abiotic factors that may exert a priming effect on these maize plants (Frost et al ., ), we speculate that Jingke968 may be naturally primed to combat O. furnacalis, because it not only had high levels of JA, but also had high levels of DIMBOA and DIMBOA‐Glc before being subjected to O. furnacalis attack, and high levels (424.20 μg/g FW) of HDMBOA‐Glc after O. furnacalis infestation.…”

The role of plant epigenetics in biotic interactions

“…Plants are a highly diversified group of sessile organisms, and as such cannot flee from changing environments. Their local persistence requires strategies that allow mitigating short-term negative impacts without compromising future fitness (Douma et al, 2017). Besides numerous abiotic factors such as temperature, light, nutrient and water availability, the plants' complex biotic environment substantially affects plant performance.…”