Pheromone transport lipophorin

The site of pheromone production in flies and cockroaches that utilize hydrocarbons is similar to that of the moths. Oenocyte cells produce the hydrocarbon pheromone which is transported by lipophorin in the hemolymph to epidermal cells throughout the body for release from the cuticular surface in general [20,21]. 

Several families of moths utilize hydrocarbons or epoxides of hydrocarbons as their sex pheromone. Oenocyte cells produce hydrocarbons that are transported through the hemolymph by lipophorin [71]. In a study using arctiid moths it was shown that sex pheromone hydrocarbons are transported on the same lipophorin particle as the hydrocarbons destined for the cuticular surface [ 17]. Therefore, specific uptake of the sex pheromone hydrocarbon occurred in pheromone glands [17]. Similar findings have been found with other moths [72-74]. The mechanism behind this specific uptake of one hydrocarbon from a potential pool of other hydrocarbons is unknown. 

Drosophila melanogaster is another dipteran where pheromone biosynthesis has been studied [92]. Adult sexually mature female D. melanogaster utilizes primarily Z7,Z11-27 H as a contact sex pheromone. The biosynthesis of this compound follows the biosynthesis of other hydrocarbon-derived pheromones (Fig. 3). It is biosynthesized in oenocytes [93], transported through the hemo-lymph by lipophorin [94], and deposited on the cuticle surface. Biosynthesis in the oenocytes follows a similar pathway [95] as that described for the house fly... 

Fig. 7 Transport of hydrocarbons and other lipids by lipophorin from site of synthesis (oenocytes) to various tissues. In the case of pheromone glands specific hydrocarbons are unloaded to be used directly as a pheromone or modified with the addition of oxygen and then released as a pheromone... 

The biosynthesis of Me3,Mel 1-29 H takes place in oenocyte cells, released into the hemolymph and transported by lipophorin to peripheral tissues (Fig. 7) [71, 231, 232]. Direct evidence for oenocytes biosynthesizing hydrocarbon has come recently with the dissociation of oenocytes from epidermal cells and in vitro incubation with labeled propionate [233]. Differential uptake of some hydrocarbons in different tissues has also been documented although the exact mechanism behind the differential placement of hydrocarbons is unknown [20,128,230,232,234]. Although the biosynthesis of hydrocarbons may not be under direct endocrine regulation supply of precursor hydrocarbon that is converted to the sex pheromone is a requirement. 

As with the other insects studied that utilize hydrocarbon sex pheromones, once Z9-23 H is produced by oenocyte cells it is released into the hemolymph. Lipophorin is the transport protein that will move the hydrocarbon to cuticu-lar tissue [21]. It was found that about 24 h were required once Z9-23 H was induced to actual deposition on the cuticular surface [237]. As is the case with other insects selective partitioning of the sex pheromone was observed with relatively larger proportions of Z9-23 H being found on the cuticular surface than in other tissues [21]. 

The third, and perhaps least understood, mechanism regulating contact pheromone production involves its transport to the cuticular surface. The detection of large amounts of hydrocarbons and pheromone internally, within the hemolymph, prompted an examination of lipid transport in B. germanica. Gu et al. (1995) and Sevala etal. (1997) isolated and purified a high density lipoprotein, lipophorin, that carries hydrocarbons, contact pheromone, and JH within the hemolymph. The accumulated evidence supports the idea that the hydrocarbons and contact pheromone components are produced by oenocytes within the abdominal integument, carried by lipophorin, and differentially deposited in the cuticle and ovaries (Fan et al.,... 

Gu, X., Quilici, D., Juarez, P, Blomquist, G. J. and Schal, C. (1995). Biosynthesis of hydrocarbons and contact sex pheromone and their transport by lipophorin in females of the German cockroach (Blattella germanica). Journal of Insect Physiology 41 257-267. 

Schal, C., Sevala, V. and Card6, R. T. (1998). Novel and highly specific transport of a volatile sex pheromone by hemolymph lipophorin in moths. Naturwissenschaften 85 339-342. 

In contrast, the hydrocarbon contact sex pheromone of the German cockroach is synthesized in Class II oenocytes associated with the abdominal stemites (Young et al., 1999 Fan et al., 2002). These large oenocytes, ranging up to 50 p in in diameter in B. germanica, have abundant mitochondria and extensive smooth endoplasmic reticulum (Fan et al., 2002). Although the oenocytes are associated with abdominal stemites, the hydrocarbons are released into the hemolymph and loaded, probably across a plasma membrane reticular system, into high-density lipophorin. The lipophorin then likely transports the hydrocarbon to epidermal cells for release onto the cuticle (Fan et al., 2002). 

Moths in the families Geometridae, Arctiidae, and some Noctuidae utilize hydrocarbons or epoxides of hydrocarbons as their sex pheromones. Hydrocarbon biosynthesis occurs in oenocyte cells that are associated with either epidermal cells or fat body cells (Wigglesworth, 1970). Once the hydrocarbons are biosynthesized, they are transported to the sex pheromone gland by lipophorin (Schal et al., 1998). The hydrocarbons can be released directly in the case of some moths or they are transformed into epoxides by addition of oxygen across one of the double bonds. 

Figure 3.7 Production of the sex pheromone in the gypsy moth, Lymantria dispar. The oenocyte cells located in the abdomen biosynthesize the alkene hydrocarbon precursor to the pheromone, 2me-Z7-18 Hc. It is transported through the hemolymph by lipophorin. The alkene is taken up by pheromone gland cells where it is acted upon by an epoxidase to produce the pheromone disparlure, 2me-18 7,8Epox.

Schal C., Sevala V., Capurro M. D. L., Snyder T. E., Blomquist G. J. and Bagneres A.-G. (2001) Tissue distribution and lipophorin transport of hydrocarbon and sex pheromones in the house fly, Musca domestica. 11 pages J. Insect Sci 1, 12. Available onhne insectscience.org/1.12. 

Figure 5.3 Schematic drawing showing transport of hydrocarbons (and other lipids) from site of synthesis (oenocytes) to cuticle surface (epicuticle) and various tissues and glands. Arrows represent hypothetical transport of hydrocarbons (and/or precursors) [legends e epicuticule p procuticule h hydrocarbons (and/or precursors) d epidermal cell c canal issuing from an epidermal cell o oenocytes 1 lipophorins fm microsome fraction (reticulum endoplasmic of oenocytes, site of hydrocarbon biosynthesis) hi hemolymph pg pheromone glands ot other tissues (ovaries)] (updated from Bagnhres, 1996).

Matsuoka, K Tabunoki, H., Kawai, T., Ishikawa, S., Yamamoto, M Sato, R. and Ando, T. (2006). Transport of a hydrophobic biosynthetic precursor by lipophorin in the hemolymph of a geometrid female moth which secretes an epoxyalkenyl sex pheromone. Insect Biochem. Mol. Biol., 36, 576-583. 

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