Pheromone glands

Fig. 9A,B GC-MS analysis of the pheromone extract of Anadevidia peponis (Noctuidae, 1 FE) treated with DMDS A TIC B mass chromatograms [141]. The mass chromatograms, which are multiplied by indicated factors, monitor the M+ of DMDS adducts derived from C10 to C16 monoenyl acetates (m/z 292,320,348, and 376) and some diagnostic fragment ions (m/z 89,117,145,173,175,203,231, and 259) to determine their double-bond position. Peaks I-VI indicate the DMDS adducts of the following components in the pheromone gland Z5-10 OAc (I),Z5-12 OAc (II),Z7-12 OAc (III), ll-12 OAc (IV),Z9-14 OAc (V), and Zll-16 OAc (VI)...

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. 

Most female moths release sex pheromones in a typical calling behavior in which the pheromone gland is extruded to release pheromone during a particular time of the photoperiod. In most cases pheromone biosynthesis coincides... 

The gene encoding PBAN was first characterized from H. zea and B. mori [134,137,138,195]. The cDNA was found to encode the 33 amino acid PBAN plus four additional peptides with a common C-terminal FXPRL sequence motif, including that of the diapause hormone of B. mori (Fig. 6). Three additional peptides with the common C-termini and sequence homology to those of H. zea and B. mori have been deduced from cDNA isolated from pheromone glands of several other moths [194,196-200]. Studies conducted to find the post-translational processed peptides indicated that PBAN was found to a greater extent in the mandibular and maxillary clusters than in the labial cluster of neurons... 

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 function of the male courtship pheromone in plethodontids was first documented in a study of Desmognathus ocoee Houck and Reagan (1990) showed that the diffusion delivery of a crude extract from the male pheromone gland increased... 

The sex pheromone communication system basically involves the release of specific chemicals from a pheromone producer (emitter), the transmission of these chemicals in the environment to a receiver, and the processing of these signals to mediate appropriate behavioral responses in the receiver. The chemicals transmitted downwind have been the most obvious targets for characterization. The code was first broken with the publication in 1959 (3) of the sex pheromone for the domesticated silkworm Bombyx mori after extraction of a half million female silkworm pheromone glands and 30 years of classical chemical analyses. The pheromone was found to be (E10, Z12)-hexadecadien-l-ol, which was called bombykol. This work showed that there was nothing magical about the communication system, and chemists around the world were "attracted" to this area of research on insect pheromones. 

FIGURE 3 Pheromone biosynthetic pathways commonly used in moth sex pheromone glands to produce precursors for specific blends of acetates, alcohols, or aldehydes. Cascades of precursors are produced by combinations of unique A- -desaturases and limited chain-shortening steps. The six precursors for the cabbage looper blend (Figure 2) are in boldface type. 

In moths, it was discovered in Helicoverpa zea that a peptide produced in the subesophageal ganglion portion of the brain complex regulates pheromone production in female moths (19). This factor has been purified and characterized in three species, Helicoverpa zea (20), Bombyx mori (21, 22), and Lymantria dispar (23). They are all a 33- or 34-amino acid peptide (named pheromone biosynthesis activating neuropeptide, PBAN) and have in common an amidated C-terminal 5-amino acid sequence (FXPRL-amide), which is the minimum peptide fragment required for pheromon-tropic activity. In the redbanded leafroller moth, it was shown that PBAN from the brain stimulates the release of a different peptide from the bursae copulatrix that is used to stimulate pheromone production in the pheromone gland found at the posterior tip of the abdomen (24). 

FIGURE 4 Proposed model for the interaction of PBAN with a receptor on the sex pheromone gland of a corn earworm female, and the resulting stimulation of acetyl-CoA carboxylase of the pheromone biosynthetic pathway. 

The asopine bug Tynacantha marginata represents a case in point of the premature designation of insect-produced compounds as pheromones. Males of this species produce a novel tricyclic sesquiterpenoid 48 from their pheromone gland , which has been designated as a putative sex pheromone [64], apparently on the basis that it is produced only by males. No assessment of the biological activity of crude extracts from the bugs, the purified compound from the bugs, or the synthetic compounds (see below) has been reported in the primary literature. 

Additional compounds found in the pheromone gland of female cigarette beetles are (2S,3R,l R)-2,3-dihyro-2-ethyl-3,5-dimethyl-6-(r-methyl-2 -oxo-butyl)-4ff-pyran-4-one 121 (P-serricorone), its (rs)-epimer (a-serricorone), and its reduction product, serricorole, 122 which shows (l/S,2/S)-configuration [245-247]. These compounds showed only weak attractivity [245], however, they obviously act as oviposition deterrents [248,249]. 

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