“Within-plant signalling by volatiles leads to induction and priming of an indirect plant defence in nature” Martin Heil and Juan Carlos Silva Bueno 2007, PNAS, 104, Plant volatiles carry both public and private messages Claudia Voelckel

Max-Planck Institute for Chemical Ecology Jena, Germany „Chemical languages“„Interacting organisms“ Plants: produce compounds that attract pollinators, repel herbivores, attract predators and inhibit competitors Herbivores: avoid, detoxify, excrete, sequester and modify plant compounds for their own purposes Examples from plant and herbivore chemical vocabularies:  Caterpillars make fatty acid-amino acid conjugates that alter the plant’s wound response  Plants make volatile organic compounds (VOC) that attract herbivore antagonists Molecule-encoded messages…

Jonathan Gershenzon, PNAS 104: Plant volatiles carry both public and private messages “Plants have never worried about compliance with the Kyoto Protocol. For millennia, they have released large amounts of gaseous compounds, such as carbon dioxide, oxygen, water vapor, and ethylene, from their foliage into the lower atmosphere. Thanks to improvements in headspace sampling techniques and mass spectrometry in the last 20 years, the list of plant volatiles has greatly expanded and now includes methanol, acetone, formaldehyde, and other short chain carbonyl compounds, plus a host of terpenes, phenylpropanoids, benzenoids, and fatty-acid derivatives. Are plants just passing gas by emitting compounds that are by-products of essential processes or do the released substances have any real function in their lives?” Volatile organic compounds (VOCs) – A bit of history  Floral scent attracts pollinators  “Talking trees”  Botanical cry for help Public messages:

T. C. J. Turlings, J. H. Tumlinson, and W. J. Lewis (1990) Exploitation of Herbivore-Induced Plant Odours by Host-Seeking Parasitic Wasps Science 250, 1251  Corn seedlings release volatiles after fed upon by caterpillars but artificially damaged seedlings don’t  parasitic wasps learn to associate volatiles with the presence of their prey Public messages 1 - “Botanical cry for help” A. Kessler and I. T. Baldwin (2001) Defensive Function of Herbivore-Induced Plant Volatile Emissions in Nature Science 291, 2141 Mimic of volatile release in wild tobacco:  Increased egg predation rates by a generalist predator and  Decreased lepidopteran oviposition rates  Through VOCs plants control herbivores “top down” and “bottom up”

Public messages 2 - “Talking trees” I. T. Baldwin, R. Halitschke, A. Paschold, C. C. v.Dahl, and C. A. Preston (2006) Volatile Signalling in Plant-Plant Interactions: ‘‘Talking Trees’’ in the Genomics Era Science 311, 812  Exposure to volatiles from damaged sagebrush primes the elicitation of defensive proteinase inhibitors in wild tobacco  Exposed plants subsequently receive less damage What do plants talk about? The probability of being attacked…

“Within-plant signalling by volatiles leads to induction and priming of an indirect plant defence in nature.” M. Heil and J. C. S. Bueno, PNAS, 104, New: The private part of volatile signalling… The model system - Phaseolus lunatus, L. Fabacae (lima bean) (E)/ (Z)-β-ocimene (Z)-3-hexenyl-acetate linalool DMNT(Z)-jasmone methyl-salicylate TMTT (E)-caryophyllene Volatile organic compounds (induced by beetles, jasmonic acid) Extrafloral nectaries (attract ants, wasps and flies) Slide provided by C. Kost

New: The private part of volatile signalling… Experiment 1: VOCs induce defences in neighbouring plants in the field Experiment 2: VOCs as a means of within-plant signalling and priming of EFN production under natural conditions Experiment 3: Support for experiment 2 with seedlings transplanted to the greenhouse

Experiment 1 Undamaged emitters Herbivore-induced emitters VOC-exposed parts:  Higher amounts of EFN  More ants  More leaves,  More growing shoot tips,  Less herbivory = part of defensive effect due to EFN-mediated increase in ant numbers Are VOCs perceived by the emitter itself?Experiment 2

Experiment 2 – EFN secretion by VOCs in the field Artificial damage of leaves 4+5 Af: Emitter shoot Cf: Emitter shoot + plastic bag Bf, Df: Receiver shoot Ef: Untreated control  Undamaged Af leaves receive external + internal signals while undamaged Cf leaves only receive internal signals  EFN response in undamaged Cf much weaker than in undamaged Af,  Intra-shoot information transfer due to VOC rather than internal signal

Experiment 2 – Priming of EFN secretion  Significant induction observed in most leaf groups  Presence of VOCs augmented response (leaves 1-3 of Af, leaves 1-3 and 4-5 of Bf)  Strongest effect in leaves exposed to highest dose of volatiles (4-5 of Bf) All leaves damaged after day 1 except previously damaged leaves (4+5 of Af, Cf) Af: Emitter shoot Cf: Emitter shoot + plastic bag Bf, Df: Receiver shoot Ef: Untreated control Priming: primed plants respond stronger once attacked themselves than non-primed plants

Experiment 3 - Setup Goal: exclude effects of root signalling, volatiles of other plants, influence of closed bags on potential internal signals Artificial damage/ beetle damage of leaves 4+5 in A, B and C Ap: Blowing VOCs from 4+5 to leaves 1-3 Bp: Blowing VOCs away from the plant Cp: Gasflow unaffected Dp: Air from uninduced 4+5 redirected to 1-3

Experiment 3 - Results  No difference in Ap and Cp and in Bp and Dp in EFN production  Bp shows that VOCs are more important than internal signalling for intra- plant communication in lima bean

Implications  Systemic spread of information in plants not just via phloem and xylem (Ryan and co-workers: wounding triggers an increase in defences in distal leaves, candidate molecules are phloem-travellers systemin and jasmonic acid) A VOC Signalling B Short-range vascular signalling C Long-range vascular signalling  Airborne within plant signalling is adaptive: foliage in close proximity often only has remote vascular links  Future studies on systemic responses of plants to local damage should control airflow to disentangle internal and external signals

Towards a deeper understanding of plant messages What’s first? Private or public talk?  Internal roles of VOCs probably evolved first  Herbivore enemies, herbivores, neighbouring plants could “eavesdrop” on VOCs with intraplant messages How do plants talk?  Who are the messengers? – green leaf volatiles and terpenes are good candidates  VOC synthesis, release, re-uptake, receptor binding, down- stream cascades (pathways and their regulators)  What are the costs and benefits of intra-plant communication? Manipulate VOC production in the field (mute and deaf plants)!

Questions?