Chemical ecology research at Rothamsted exploits long established and acclaimed expertise in the identification and development of pheromones and other semiochemicals (signalling chemicals) for use in crop protection. The work now includes molecular genetic approaches to allow us to understand how semiochemicals (small lipophilic molecules; SLMs) can be generated as plant secondary metabolites and delivered through seed via conventional breeding or GM technologies. The group has developed companion plants that release semiochemicals for crop protection in smallholder farming in Africa.
1.Identification of pheromones and other semiochemicals involved in interactions between insects and between insects and their host plants
The primary targets of this objective are aphids, but other sucking pests and chewing insects are studied. This overarching objective uses advanced chemical analytical techniques to study very low levels of semiochemicals produced by arthropods, their hosts/non-hosts, and antagonistic plants, in conjunction with arthropod electrophysiology where appropriate. Tentative molecular structures are proposed using advanced spectroscopic techniques (MS, NMR) and confirmed by obtaining authentic samples via either chemical synthesis, by isolation from natural sources, or by chemical/genetic transformation of plants. The biosynthesis of semiochemicals is investigated using synthesized biosynthetic precursors and mass spectrometry. Plant production of semiochemicals is being developed for renewable resource production. Semiochemical targets include pheromones, allelochemicals and arthropod-derived elicitors of plant defence
2.Investigation of the molecular interactions between semiochemicals and their recognition proteins
Previous use of bioinformatics (and genome sequences) combined with molecular techniques have identified genes and proteins involved in the detection of semiochemicals and the generation of a behavioural response in insects. The next step is to determine the interactions between the signals, which is being provided by chemical synthesis, and odorant-binding proteins and the olfactory receptors.
3.Elucidation of the molecular basis of natural stress-related induction of plant defences to insects
Small lipophilic molecules (SLMs) responsible for signalling between plants and for activating plant defence naturally are being investigated and developed, both for use in activating defence of current crop plants and in crops genetically modified to respond to signalling SLMs by “switching on” defence secondary metabolism genetics. The work includes identification of novel SLMs that act as signals between and within plants and particularly where penetration through the plant cuticle does not require tissue damage, which includes volatile signals and those produced by insect colonisation prior to tissue damage, e.g. during oviposition. The defence activator, cis-jasmone, is being studied at the molecular level to understand the recognition and signal transduction processes for use more widely with new signals being identified and developed. Direct induction of defence is being investigated at both the primary (deterrence of herbivores) and secondary (exploitation of biological control) levels, with some effort to identify new priming signals where problems of phytotoxicity associated with current priming agents can be overcome.
4. Deployment of semiochemical strategies at the farm scale
Opportunities for delivering semiochemical-based management strategies via the seed using plant breeding or GM, by incorporation of the gene(s) responsible for the biosynthesis of semiochemicals, that can be switched on upon exposure to natural plant activators (see previous objective). This is exemplified by current work to produce transgenic wheat emitting the aphid alarm pheromone and testing the effect upon aphid colonisation in the field, and the development of new elite wheat cultivars producing allelopathicbenzoxazinoids that reduce aphid development It is also highly likely that the manipulation of ratios of compounds emitted by crop plants would make them less attractive to pests (see previous objective).Rothamsted is in a unique position of being able to test the robustness of breeding/GM strategies in the field, and this will be a vital component of new elite crop cultivars. This will require both testing the direct and indirect effects of the transgenic plants on target pests, i.e. aphids and their beneficial natural enemies.
Professor Pickett, Michael Elliott Distinguished Research Fellow at Rothamsted Research, elected to NAS as Foreign Associate
Professor John Pickett, Michael Elliott Distinguished Research Fellow and Scientific Leader of Chemical Ecology, at Rothamsted Research, Harpenden, is among the 84 new members and 21 foreign associates elected as fellows of the National Academy of Sciences.
Prof John A. Pickett FRS CBE
Toby J.A. Bruce, BSc, MSc, PhD
John C. Caulfield, PhD
Tony M. Hooper, BA, PhD
Lesley E. Smart, BSc
Christine M. Woodcock
Jing-Jiang Zhou, PhD
Gia Aradottir, PhD
Stephen S. Barasa, PhD
Keith Chamberlain, PhD
Michaela C. Matthes, MSc, PhD
Jozsef Vuts, PhD
Andre F Sarria, PhD
Janet L. Martin, MIBiol
Barry J. Pye