title: Gall volatiles defend aphids against a browsing mammal.
abstract: BACKGROUND
  Plants have evolved an astonishing array of survival strategies. To defend against insects, for example, damaged plants emit volatile organic compounds that attract the herbivore's natural enemies. So far, plant volatile responses have been studied extensively in conjunction with leaf chewing and sap sucking insects, yet little is known about the relationship between plant volatiles and gall-inducers, the most sophisticated herbivores. Here we describe a new role for volatiles as gall-insects were found to benefit from this plant defence.
  
  
  RESULTS
  Chemical analyses of galls triggered by the gregarious aphid Slavum wertheimae on wild pistachio trees showed that these structures contained and emitted considerably higher quantities of plant terpenes than neighbouring leaves and fruits. Behavioural assays using goats as a generalist herbivore confirmed that the accumulated terpenes acted as olfactory signals and feeding deterrents, thus enabling the gall-inducers to escape from inadvertent predation by mammals.
  
  
  CONCLUSIONS
  Increased emission of plant volatiles in response to insect activity is commonly looked upon as a "cry for help" by the plant to attract the insect's natural enemies. In contrast, we show that such volatiles can serve as a first line of insect defences that extends the 'extended phenotype' represented by galls, beyond physical boundaries. Our data support the Enemy hypothesis insofar that high levels of gall secondary metabolites confer protection against natural enemies.
authors.affiliation: Bio-Protection Research Centre, Lincoln University, PO Box 85084, Lincoln 7647, New Zealand. michael.rostas@lincoln.ac.nz.
authors.forename: Michael
authors.initials: M
authors.lastname: Rostás
authors.forename: Daniel
authors.initials: D
authors.lastname: Maag
authors.forename: Makihiko
authors.initials: M
authors.lastname: Ikegami
authors.forename: Moshe
authors.initials: M
authors.lastname: Inbar
mesh_terms: D000818:Animals; D001042:Aphids; D006041:Goats; D060434:Herbivory; D027927:Pistacia / Q000737:chemistry* / Q000502:physiology*; D018515:Plant Leaves; D055549:Volatile Organic Compounds / Q000378:metabolism*
chemical_list: D055549:Volatile Organic Compounds
references.citation: Mol Phylogenet Evol. 2004 Aug;32(2):504-11
references.pmid: 15223033
references.citation: Proc Natl Acad Sci U S A. 2000 Nov 21;97(24):13184-7
references.pmid: 11078506
references.citation: Biol Rev Camb Philos Soc. 1996 Feb;71(1):27-79
references.pmid: 8603120
references.citation: Science. 2012 Oct 5;338(6103):113-6
references.pmid: 23042894
references.citation: PLoS Biol. 2009 Aug;7(8):e1000179
references.pmid: 19707266
references.citation: Curr Opin Plant Biol. 2006 Aug;9(4):421-7
references.pmid: 16723271
references.citation: Annu Rev Entomol. 2004;49:175-92
references.pmid: 14651461
references.citation: Science. 2000 Mar 24;287(5461):2254-7
references.pmid: 10731145
references.citation: Curr Opin Plant Biol. 2009 Aug;12(4):479-85
references.pmid: 19467919
references.citation: Plant Physiol. 1991 May;96(1):44-9
references.pmid: 16668184
references.citation: J Chem Ecol. 1987 Mar;13(3):437-49
references.pmid: 24301886
references.citation: J Chem Ecol. 2012 May;38(5):496-8
references.pmid: 22532245
references.citation: New Phytol. 2008;178(3):657-71
references.pmid: 18331430
references.citation: Evolution. 1998 Dec;52(6):1686-1696
references.pmid: 28565317
references.citation: Plant Signal Behav. 2008 Jul;3(7):503-4
references.pmid: 19704500
references.citation: Oecologia. 1987 Jan;71(2):254-261
references.pmid: 28312253
references.citation: Proc Natl Acad Sci U S A. 2006 Jan 24;103(4):1129-34
references.pmid: 16418295
references.citation: J Agric Food Chem. 2004 Feb 11;52(3):572-6
references.pmid: 14759150
references.citation: Mol Plant Microbe Interact. 2009 May;22(5):551-9
references.pmid: 19348573
references.citation: Proc Natl Acad Sci U S A. 2002 Nov 26;99(24):15486-91
references.pmid: 12438683
references.citation: Annu Rev Plant Biol. 2012;63:431-50
references.pmid: 22404468
references.citation: Curr Biol. 2010 Aug 10;20(15):R628-9
references.pmid: 20692607
references.citation: Trends Plant Sci. 2010 Mar;15(3):167-75
references.pmid: 20047849
references.citation: J Chem Ecol. 2005 Jan;31(1):151-66
references.pmid: 15839487
references.citation: Oecologia. 1986 Sep;68(3):437-445
references.pmid: 28311792
references.citation: Nat Chem Biol. 2007 Jul;3(7):408-14
references.pmid: 17576428
references.citation: Proc Biol Sci. 2003 Aug 7;270 Suppl 1:S12-4
references.pmid: 12952623