Volatile signals

In the natural world, carotenoid oxidation products are important mediators presenting different properties. Volatile carotenoid-derived compounds such as noriso-prenoids are well known for their aroma properties. Examples include the cyclic norisoprenoid P-ionone and the non-cyclic pseudoionone or Neral. Carotenoid oxidation products are also important bioactive mediators for plant development, the best-known example being abscisic acid. Apo-carotenoids act as visual and volatile signals to attract pollination and seed dispersal agents in the same way as carotenoids do, but they are also plant defense factors and signaling molecules for the regulation of plant architecture. 

Singer A.G., Beauchamp G. and Yamazaki K. (1997). Volatile signals of the major histocompatibility complex in male mouse urine. Proc Natl Acad Sci 94, 2210-2214. 

Females of the cowpea weevil, Callosobruchus maculatus, release a male attracting pheromone from the tip of their abdomen. The volatile signal contains five unsaturated, branched C8-acids 208-212 [376,377]. Individual compounds proved to be active while mixtures showed additive effects. Similarly, compounds 208 and 209 have been identified as the female produced sex pheromone of C. subinnotatus [378], while 209 had been described as the sex pheromone of C. analis [379]. However, GC-MS analyses of female produced volatiles of C. analis failed to detect any of the C. maculatus compounds, but did find an unidentified C8-acid with a retention time different from any of the C. maculatus acids [377]. 

Urine composition depends on testosterone, as in male mice (Schwende etal, 1986) and the wolf, Canis lupus (Raymer etal., 1986). In the wolf, these volatiles signal both sex and sexual maturity (Raymer eta/., 1986). Similarly, composition of female urine changes with the estrus cycle (Schwende etal., 1986). 

Gouingucne, S. (2000). Specificity and variability in induced volatile signalling in maize plants, University of Neuchatel, Switzerland. 

The small males of Nephila clavata cohabit with the much larger females in their web, and copulation takes place immediately after the final molt. Olfactometer tests showed that freshly molted females are much more attractive than older ones. Acetone extracts of the body surface of freshly molted females contained the active principle. Miyashita and Hayashi (1996) suggested that the volatile signal may originate from the molting fluid. 

Insects communicate through the use of a great variety of volatile pheromones. As mentioned in Chapter 8, Section A,l, some moths utilize acetate esters of various isomers of A7 and A11 unsaturated C14 fatty acids as sex pheromones. Some other moths convert the trans-l 1 -tetradecenyl acetate into the corresponding C14 aldehyde or alcohol, while others use similar compounds of shorter (Cn - C12) chain length.143 Some ants use ketones, such as 4-methyl-3-heptanone, as well as various isoprenoid compounds and pyrazines as volatile signaling compounds.144 Other insects also utilize isoprenoids,145 alkaloids,146 and aromatic substances as pheromones. 

Ethylene (=CH2 = CH2) (alkene) Volatile signal in plants Apoptotic (DNA fragmentation) (plants)... 

Several hundred volatile isoprenoid substances that interfere with insect larval moulting have so far been resolved from plants and such phytoecdysones will be dealt with in Chapter 11, which is concerned with development-perturbing compounds binding to cytosolic hormone receptors. It must also be noted that plant cells within a plant (and indeed whole plants themselves) can communicate with each other via volatile signalling bioactives... 

Paschold A, Halitschke R, Baldwin IT. Using mute plants to translate volatile signals. Plant J. 2006 45 275-291. 

BALDWIN, I.T., KESSLER, A., HALITSCHKE, R., Volatile signaling in plant-plant-herbivore interactions what is real , Curr. Opin. Plant Biol., 2002, 5, 351-354. 

Tryptophan synthase (TS) catalyzes the ultimate step in tryptophan biosynthesis (details see Fig. 4.2). Indole and benzoxazinoid secondary metabolite formation branches from this pathway. The two lyases IGL and BXl cleave indole-3-glycerol phosphate into indole (and glycerolaldehyde-3-phosphate, not shown) and serve as committing enzymes for indole derived secondary metabolites. Indole produced by IGL directly functions as volatile signal. Indole produced by BXl is converted by other enzymes (BX2-BX9) to benzoxazinoids that have an important function in the chemical defense of grasses. 

However, unlike small molecule pheromones in terrestrial invertebrates such as moths, many terrestrial mammals may increase the activity of their small molecule pheromones by interaction with carrier proteins. For example, in mice the small volatile molecules are presented as ligands of Mouse Urinary Proteins (MUPs). The MUPs provide a slow release of the volatile signal and the highly variable MUPs may also provide individuality to the signal (Hurst et al., 2001 Beynon and Hurst, this volume Hurst and Beynon, this volume). As far as I know, there are no examples among the invertebrates of combining small molecules with proteins. 

In conclusion, cloacal secretions have the following behavioral effects on brown tree snakes I) they act as a pheromone that inhibits male courtship behavior, and 2) when aged, they act as a chemical signal and/or chemical irritant that that elicits defensive behaviors from the snakes. Our results represent a significant part of only a small handful of studies that have empirically demonstrated behavioral effects of cloacal secretions, despite the attention they have historically received in the literature (Mason, 1992). The data also demonstrate the effects of volatile chemical signals on snake behavior the effects of non-volatile signals on snake behavior have been more commonly studied (Mason, 1992). 

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