Within-plant signaling by volatiles leads to induction and priming of an indirect plant defense in nature

Abstract

Plants respond to herbivore attack with the release of volatile organic compounds (VOCs), which can attract predatory arthropods and/or repel herbivores and thus serve as a means of defense against herbivores. Such VOCs might also be perceived by neighboring plants to adjust their defensive phenotype according to the present risk of attack. We exposed lima bean plants at their natural growing site to volatiles of beetle-damaged conspecific shoots. This reduced herbivore damage and increased the growth rate of the exposed plants. To investigate whether VOCs also can serve in signaling processes within the same individual plant we focused on undamaged ''receiver'' leaves that were either exposed or not exposed to VOCs released by induced ''emitter'' leaves. Extrafloral nectar secretion by receiver leaves increased when they were exposed to VOCs of induced emitters of neighboring plants or of the same shoot, yet not when VOCs were removed from the system. Extrafloral nectar attracts predatory arthropods and represents an induced defense mechanism. The volatiles also primed extrafloral nectar secretion to show an augmented response to subsequent damage. Herbivore-induced VOCs elicit a defensive response in undamaged plants (or parts of plants) under natural conditions, and they function as external signal for within-plant communication, thus serving also a physiological role in the systemic response of a plant to local damage.ant-plant interaction ͉ extrafloral nectar ͉ indirect defense ͉ lima bean ͉ plant-plant communication

Airborne Induction and Priming of Plant Defenses against a Bacterial Pathogen

“…Airborne induction and priming of direct and indirect plant defenses against herbivores has repeatedly been reported (Engelberth et al, 2004;Heil and Kost, 2006;Kessler et al, 2006;Frost et al, 2007;Heil and Silva Bueno, 2007;Ton et al, 2007). Herbivore resistance, however, is usually dependent on jasmonate signaling (Farmer et al, 2003;Wasternack, 2007;Heil and Ton, 2008), while SAR to biotrophic pathogens is mainly regulated via salicylate signaling (Hunt and Ryals, 1996;Durrant and Dong, 2004;Heil and Ton, 2008).…”

“…In particular, green-leaf volatiles and other herbivore-induced volatile organic compounds (VOCs) can mediate the systemic response of plants to local herbivore damage (Karban et al, 2006;Frost et al, 2007;Heil and Silva Bueno, 2007). Since such VOCs move freely in the air, they may also affect neighboring plants and then mediate the phenomenon of "plant-plant communication," which has been found in taxonomically unrelated plants such as Arabidopsis (Arabidopsis thaliana), alder (Alnus glutinosa), corn (Zea mays), lima bean (Phaseolus lunatus), maple (Acer saccharum), sagebrush (Artemisia tridentata), and wild tobacco (Nicotiana attenuata; Baldwin and Schultz, 1983;Rhoades, 1983;Tscharntke et al, 2001;Engelberth et al, 2004;Heil and Kost, 2006;Karban et al, 2006;Paschold et al, 2006;Heil and Silva Bueno, 2007;Ton et al, 2007;Godard et al, 2008).…”

The origin and dynamic evolution of chemical information transfer

“…For example, plants release volatiles as private messages from damaged parts to inform distant parts of the same plants about the imminent risk of attack [41]. The adaptive significance is that the gaseous information transfer is quicker than a systemic response by the plant.…”

Volatile terpenoids: multiple functions, biosynthesis, modulation and manipulation by genetic engineering

“…In the case of herbivore damage, significant amounts of volatile terpene blends are emitted from lima bean leaves to stimulate the adjacent leaves to boost nectar secretion to attract herbivore enemies (Heil and Bueno 2007). Developments in chemical ecology increasingly confirm terpenoids' defensive role.…”