title: Herbivore-induced, indirect plant defences.
abstract: Indirect responses are defensive strategies by which plants attract natural enemies of their herbivores that act as plant defending agents. Such defences can be either constitutively expressed or induced by the combined action of mechanical damage and low- or high-molecular-weight elicitors from the attacking herbivore. Here, we focus on two induced indirect defences, namely the de novo production of volatiles and the secretion of extrafloral nectar, which both mediate interactions with organisms from higher trophic levels (i.e., parasitoids or carnivores). We give an overview on elicitors, early signals, and signal transduction resulting in a complex regulation of indirect defences and discuss effects of cross-talks between the signalling pathways (synergistic and antagonistic effects). In the light of recent findings, we review molecular and genetic aspects of the biosynthesis of herbivore-induced plant volatiles comprising terpenoids, aromatic compounds, and metabolites of fatty acids which act as infochemicals for animals and some of which even induce defence genes in neighbouring plants. Finally, ecological aspects of these two indirect defences such as their variability, specificity, evolution as well as their ecological relevance in nature are discussed.
authors.affiliation: Max Planck Institute for Chemical Ecology, Department of Bioorganic Chemistry, Hans-Knöll-Strasse 8, D-07745 Jena, Germany.
authors.forename: Gen-ichiro
authors.initials: G
authors.lastname: Arimura
authors.forename: Christian
authors.initials: C
authors.lastname: Kost
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Boland
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003517:Cyclopentanes / Q000737:chemistry / Q000378:metabolism; D004463:Ecology; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006790:Host-Parasite Interactions; D015394:Molecular Structure; D009822:Oils, Volatile / Q000737:chemistry / Q000378:metabolism; D054883:Oxylipins; D010937:Plant Growth Regulators / Q000737:chemistry / Q000378:metabolism; D018521:Plant Physiological Phenomena; D010944:Plants / Q000737:chemistry*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D003517:Cyclopentanes; D005227:Fatty Acids; D009822:Oils, Volatile; D054883:Oxylipins; D010937:Plant Growth Regulators; C011006:jasmonic acid