SCHULTZ, J.C.: Shared signals and the potential for phylogenetic espionage between plants and animals

Our understanding of responses to biotic and abiotic stimuli has developed separately for plants and animals. But recent biochemical and molecular work is producing a growing list of elements involved in diverse responses that are common to both kingdoms. Some of the more interesting examples of these are reviewed, including prostaglandin/octadecanoid-mediated responses to wounding, oxidative defenses, steroid- and flavonoid-based signalling systems, and pathogen-recognition mechanisms. Some of these similarities probably represent evolutionary convergence, while others may be ancestral to the development of plants and animals. Whatever the origins, they permit widely divergent taxa to exploit each other’s signalling systems (“phylogenetic espionage”). The ecological and evolutionary consequences, of such overlaps are highlighted. These include the existence of pathogens that can cause disease in plants and animals (e.g., strains of Pseudomonas aeruginosa), the ability of herbivores to manipulate plant disease and anti-herbivore responses and enhance plant quality; the usurpation of microbial mechanisms and genes by parasitic insects, herbivorous animals, and plants; the evolution of plant defenses that exploit signalling systems shared by animals; and the medicinal use of plants by humans. Comparative study of the signalling and response mechanisms used by plants, animals, and microbes to deal with dynamic environments provides novel and useful insights to the ecology and evolution of interactions across kingdoms. Some of these insights suggest new ways in which we might exploit plants, animals, and microbes to our own benefit.