Early Herbivore Alert: Insect Eggs Induce Plant Defense

Abstract

Plants are able to "notice" insect egg deposition and to respond by activating direct and indirect defenses. An overview of these defenses and the underlying mechanisms is given from a tritrophic perspective. First, the interface between plant and eggs is addressed with respect to the mode of attachment of eggs on the plant surface. It is elucidated which plant cells might respond to components from insect eggs or the egg deposition. The scarce knowledge on the elicitors associated with the eggs or the egg-laying female is outlined. Since endosymbiotic microorganisms are often present on the eggs, and microorganisms are also abundant on the leaf surface, the role of these hidden players for eliciting oviposition-induced plant responses is considered. Furthermore, the question of which physiological and molecular processes are induced within the plant in response to egg deposition is addressed. Second, studies on the response of the herbivorous insect to oviposition-induced plant defenses are outlined. Third, the importance of oviposition-induced plant volatiles and contact cues for host and prey location of parasitoids and predators is discussed in the context of other informative chemicals used by carnivores when searching for food. Finally, physiological and ecological costs of oviposition-induced plant responses are addressed.

EAG-Active Herbivore-Induced Plant Volatiles Modify Behavioral Responses and Host Attack by An Egg Parasitoid

“…Egg parasitoids are less expected to use plant-derived cues or to learn; instead, they are likely to use host-derived cues (i.e., host adult pheromones) that are highly predictable within and between generations during foraging (Vet et al 1995). Recent studies have shown that egg parasitoids use not only short-distance (host-associated) cues but also may use long-distance volatiles, such as those associated with the host plant (Meiners and Hilker 1997;Hilker et al 2002;Hilker and Meiners 2006). Because hostplant volatiles are highly detectable but less reliable than host-associated odors, learning might be critical for egg parasitoids that employ host-plant volatiles in host finding (e.g.…”

“…The role of feeding-induced plant volatiles in hosthabitat location by natural enemies is well documented (Turlings et al 1991;Dicke et al 1993;Tumlinson et al 1993;Birkett et al 2003;Wei et al 2007). Recent studies also have demonstrated the importance of ovipositioninduced volatiles in the host-searching behavior of egg parasitoids Colazza et al 2004;Manrique et al 2005;Mumm et al 2005;Hilker and Meiners 2006). Exploitation of chemical signaling by plants that attract natural enemies has potential for enhancing biological control in agroecosystems (Hunter 2002).…”

Is quality more important than quantity? Insect behavioural responses to changes in a volatile blend after stemborer oviposition on an African grass

“…Recently, it has been observed that plants increase volatile emission even at the earliest stage of herbivore attack, namely oviposition (Colazza et al 2004;Hilker & Meiners 2006). This reduces further colonization by the herbivore itself and activates indirect defence, whereby natural enemies are attracted even before the larva has emerged.…”

Response of the parasitoidTelenomus podisito induced volatiles from soybean damaged by stink bug herbivory and oviposition

“…Parasitoids of herbivore eggs have evolved responses to the subtle changes in plant chemistry caused by herbivore oviposition in order to successfully find their hosts (reviewed by Hilker and Meiners 2006). The elicitor in the oviduct secretion of one herbivore has been partially characterized , and there is evidence that it affects systemic jasmonate-mediated responses Mumm et al 2003).…”