Cross-Kingdom Cross-Talk: Hormones Shared by Plants and Their Insect Herbivores

Dynamic defense responses plants exhibit when attacked by insects are probably as important ecologically as constitutive defenses were once thought to be. Plants recognize and respond to interspecific differences among insects and microbes, and some insects appear to manipulate plant signaling and response systems. These interactions are based on an exchange of signals among plant, insect, and microbes. Many of these signals are hormones, and a surprising number are common to both kingdoms. Fatty-acid-based hormones provide a particularly good example, and preliminary data suggesting that plant defense responses can be mediated by common insect hormones and signals (prostaglandins) are presented. The evolutionary and ecological implications of shared signals and signal-stealing are diverse and can greatly improve our understanding of plant–pest interactions.