How isomerisation of green leaf volatiles affects plant-insect interactions

Summary

Plants continuously emit organic volatiles into the air, but upon herbivory the amounts increase dramatically. Emission of herbivore-induced plant volatiles, i.e. especially of terpenoids, aromatic compounds and C-6 based "green leaf volatiles" (GLVs), leads to the attraction of foraging natural enemies of herbivores and therefore is referred to as indirect plant defence. We recently discovered that the increased emission of (E)-isomers of GLVs, induced in wild tobacco (Nicotiana attenuata) by tobacco hornworm (Manduca sexta) feeding, strongly increased the foraging efficiency of its natural predators in nature. Surprisingly, the conversion of the plant's (Z)-aldehydes to (E)-aldehydes was solely and directly due to isomerase activity in the herbivore's oral secretions (Allmann et al (2010), Science 329). The fact that the insect thus betrays itself raises an intriguing question: why did evolution not select against the presence of this enzyme? Here we propose to characterize the enzyme responsible for GLV isomerisation and to elucidate its function in the caterpillar's physiology, life history and ecology. First we will purify the enzyme, clone the corresponding gene and cDNA, and characterize the enzymatic properties; second we will describe the expression and activity throughout the hornworm's life cycle; thirdly we will manipulate its expression to investigate the consequences of increased or decreased emission of GLV (E)-isomers for the caterpillar's growth, development and immune response. Finally, we will investigate the costs and benefits of GLV-isomerisation by tobacco hornworms under natural conditions in the field. Doing so we expect to learn which physiological or ecological benefits have allowed the insect to maintain this treacherous enzyme.

Output

Scientific article

Details

Project number

821.02.027

Main applicant

Prof. dr. M.A. Haring

Affiliated with

Universiteit van Amsterdam, Faculteit der Natuurwetenschappen, Wiskunde en Informatica, Swammerdam Institute for Life Sciences (SILS)

Team members

Dr. S. Allmann, Dr. E. Spyropouplou

Duration

01/01/2012 to 13/09/2016