Perception host plant

Different insect species posses different gustatory receptor cells, their response spectra being adapted to the perception of chemical components distributed in their host plant species (9 ). Taste perception in P. brassicae larvae forms a representative example for phytophagous insects, which are able to discriminate a number of compounds like sugars, amino acids, salts, and secondary plant substances acting as feeding inhibitors or feeding incitants (3,6,, 10). 

Matsuo T, Sugaya S, Yasukawa J, Aigaki T, Fuyama Y (2007) Odorant-binding proteins OBP57d and OBP57e affect taste perception and host-plant preference in Drosophila sechellia. PLoS Biol 5 ell8... 

Herbivores can typically sense suitable host plants using olfactory cues from long distance. Many volatile terpenoids bear the essential information in their molecular structure. Different stereo isomers of the same compound may result in different response when sensed by insect antennae or the olfactory sensors in the nose of vertebrate animals. Another important factor affecting signal perception and behavioral response in herbivore is the relative proportion of different volatile compounds, terpenoids or other volatiles, in the odor plume released by a plant. CombinatiOTi of certain monoterpenes and sesquiterpenes are very distinctive in certain plant families. Specialist herbivore species can separate these combinations from similar monoterpenes released by other plants, because of their strict ratio in the host species. 

Contact chemoreception of the dry plant surface is basically different from the well-studied perception of aqueous solutions. Since the stimulating compounds are in a dry state it may be that their distribution is not continuous and/or at a very low concentration. Thus not every contact between a sensillum tip and the plant would result in a stimulation. Although speculative, this may explain the specific behavior of various insect species after contacting plant leaves two female flies (P. rosae, D. brassicae) perform so called oviposition runs, on host leaves of about 20-30 s duration (Stadler, 1977,1978). Locusts make rapid vibrations (10-15 times per second) with the palps contacting the potential food plant surface. Blaney and Duckett (1975) showed that this palpation increases the amount of sensory input to the CNS by allowing disadap-tation of chemoreceptors between contacts. This must also be true for the tarsal hairs of two flies mentioned above. Some butterflies use the fore tarsi to drum or tap the plant surface prior to oviposition (Ma and Schoonhoven, 1973 ... 

Initial detection by insects and other invertebrates of unsuitable hosts can involve the perception of deterrent volatile compounds released from their leaves. Such emissions benefit the survival of the emitter and are hence known as allomones. The second stage of non host avoidance involves the encountering of unfavourable secondary defence metabolites within plant tissues. 

Cote, F., Ham, K.-S., Hahn, M.G., and Bergman, C.W. (1998). Oligosaccharide elicitors in host-pathogen interactions generation, perception and signal transduction. In Biswas, B.B. and Das, H. (Eds), Subcellular Biochemistry, Vol. 29, Plant-microbe interactions. Plenum Press, New York, pp. 385 31. 

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