Indirect defence via tritrophic interactions

Abstract

Review SummaryMany plants interact with carnivores as an indirect defence against herbivores. The release of volatile organic compounds (VOCs) and the secretion of extrafloral nectar (EFN) are induced by insect feeding, a response that is mediated by the plant hormone, jasmonic acid. Although VOCs mainly attract predatory mites and parasitic wasps, while EFN mainly attracts ants, many more animal-plant interactions are influenced by these two traits. Other traits involved in defensive tritrophic interactions are cellular food bodies and domatia, which serve the nutrition and housing of predators. They are not known to respond to herbivory, while food body production can be induced by the presence of the mutualists. Interactions among the different defensive traits, and between them and other biotic and abiotic factors exist on the genetic, physiological, and ecological levels, but so far remain understudied. Indirect defences are increasingly being discussed as an environmentally-friendly crop protection strategy, but much more knowledge on their fitness effects under certain environmental conditions is required before we can understand their ecological and evolutionary relevance, and before tritrophic interactions can serve as a reliable tool in agronomy.New Phytologist (2008) 178:

Herbivory-induced volatiles function as defenses increasing fitness of the native plant Nicotiana attenuata in nature

“…They attract and inform the third trophic level, predators or parasitoids, resulting in increased attacks on herbivores (Turlings and Wäckers, 2004). Indirect defenses are widespread and include domatia, extrafloral nectar, and food bodies which provide shelter and nutrition for predators and parasitoids, as well as herbivory-induced plant volatiles (HIPVs) which convey information about feeding herbivores (Heil, 2008). Field studies with the native tobacco Nicotiana attenuata , a desert annual, and with maize have shown that HIPVs can reduce herbivore loads by 24% to more than 90%, by increasing both predation and parasitization of herbivores (Kessler and Baldwin, 2001; Rasmann et al, 2005; Halitschke et al, 2008; Degenhardt et al, 2009; Allmann and Baldwin, 2010) and deterring herbivore oviposition (Kessler and Baldwin, 2001).…”

The obscure events contributing to the evolution of an incipient sex chromosome in Populus: a retrospective working hypothesis

“…Populus and other members of the Salicaceae family are known to produce antimicrobial and antifungal compounds in nectary found near meristematic tissues, and that these compounds contribute to plant adaptive success (Heil 2008;Thadeo et al 2008). A gas chromatography-mass spectrometry (GC-MS) analysis of the metabolomic profiles of expanding floral buds of 16 trees (12 females and 4 males) from two Populus species (Populus deltoides and Populus nigra) was conducted to determine whether secondary metabolites were correlated with gender (Table 2).…”

Comparative analyses of transcriptome and proteome in response to cotton bollworm between a resistant wild soybean and a susceptible soybean cultivar

“…The direct defense are conferred by some secondary metabolites, proteinase inhibitors (PIs) and physical barriers, which have toxic, repellent or anti-digestive effects on the performance of insect life (Wu and Baldwin 2009). The indirect defense means that the plants gain the protection by emitting some volatile compounds that attract the natural enemies of herbivores (Heil 2008;Kessler and Baldwin 2002). In addition to the above definition, the plant defense against herbivory insects can also be categorized as constitutive and induced defenses based on the timing of defense activation (Gatehouse 2002).…”