Attractiveness of Host Plants at Different Growth Stage to Kudzu Bug, Megacopta cribraria (Heteroptera: Plataspidae): Behavioral Responses to Whole Plant and Constitutive Volatiles.

The kudzu bug, Megacopta cribraria (Fabricius), is an invasive pest of soybeans, Glycine max (L.) Merr., that has recently been detected in the United States. This study investigated whether there was a differential attraction of adult bugs to soybean growth stages, and whether the attraction was related to soybean constitutive volatiles. Greenhouse choice assays examined the behavioral orientation preference of adult bugs exposed to four growth stages of whole soybean plants: vegetative (V2), flowering (R1), pod (R3), and seed (R5). Results show that significantly more adults landed on plants in the early reproductive stage R1 than in other stages. Laboratory olfactometer assays also demonstrate that significantly more adult bugs were attracted to R1 plants, with females responding more strongly than males. Both greenhouse and olfactometer assays indicate that the differential attraction of adult bugs to soybean growth stages was mediated by plant constitutive volatiles. These results offer an insight into kudzu bug chemical and behavioral ecology and thus are of great significance for optimizing the timing of field scouting and treatment as well as the development of soybean pest management programs.

Factors influencing aversive learning in the oriental fruit fly, Bactrocera dorsalis.

Parameters such as the intensity of conditioned and unconditioned stimuli, the inter-trial interval, and starvation time can influence learning. In this study, the parameters that govern aversive learning in the oriental fruit fly, Bactrocera dorsalis, a serious pest of fruits and vegetables, were examined. Male flies were trained to associate the attractive odorant methyl eugenol, a male lure, with a food punishment, sodium chloride solution, and the conditioned suppression of the proboscis-extension response was investigated. We found that high methyl eugenol concentrations support a stronger association. With increasing concentrations of sodium chloride solution, a steady decrease of proboscis-extension response during six training trials was observed. A high level of learning was achieved with an inter-trial interval of 1-10 min. However, extending the inter-trial interval to 15 min led to reduced learning. No effect of physiological status (starvation time) on learning performance was detected, nor was any non-associative learning effect induced by the repeat presentation of odor or punishment alone. The memory formed after six training trials could be retained for at least 3 h. Our results indicate that aversive learning by oriental fruit flies can be affected by odor, punishment concentration and inter-trial interval.

Study of the obp5 gene in Apis mellifera ligustica and Apis cerana cerana.

Apis mellifera ligustica and A. cerana cerana exhibit differences in olfactory sensitivity to odors from nectariferous plants and diseased broods. It is presumed that the differences in odorant-binding proteins (OBPs) between these 2 species contribute to their olfactory sensitivity. We compared the sequences, temporal expression pattern, and binding properties of the 2 OBP-encoding genes. We cloned the Amobp5 and Acobp5 genes. Among the ligands tested, phenethyl acetate was the most variable, with AcOBP5 showing high affinity and AmOBP5 having no apparent affinity for this ligand. While AmOBP5 had high affinity to both benzyl alcohol and 2-phenylethanol, the binding affinity of AcOBP5 to these compounds was moderate. However, the fluorescence intensity of these compounds was not decreased below 50%; thus, the dissociation constants could not be calculated. The Amobp5 gene showed significantly higher expression in 10- and 15-day-old workers than in other stages, while the Acobp5 gene had the highest expression in 30-day-old workers. Both the Amobp5 and Acobp5 genes had the lowest expression level in 1-day-old workers. These results suggest that the binding properties and temporal expression patterns of the obp5 genes in A. mellifera and A. cerana play a critical role in the olfactory sensitivity of workers.

Analysis of phytoecdysteroids in cultured plants of Ajuga nipponensis makino.

Cultured plants of Ajuga nipponensis contained cyasterone (1), ajugasterone C (2), cyasterone-22-acetate (3) and 22-dehydrocyasterone (4) based on HPLC and NMR data, whereas 20-hydroxyecdysone was not detectable. The presence of compounds 2 4 is reported for the first time in this species. Compound 1 is the main phytoecdysteroid component found in both preblossom and blossom plants, but the latter contained higher amount than the former. Compared with other parts of the plant, the highest percentage of 1 and 3 occurred in leaves, amounting to 60.1% and 88.0% respectively, whereas the flowers contained mainly 2, which represented 72.8% of the total amount in whole plant. The contents of phytoecdysteroids in stems were very low.

Analysis of characteristic human female axillary odors: Qualitative comparison to males.

Odors produced in the human female axillae are of both biological and commercial importance. Several studies have suggested that extracts from female underarm secretions can alter the length and timing of the female menstrual cycle. In addition, more than 1.6 billion dollars are spent annually on products to eliminate or mask the axillary odors. Our recent studies have determined that the characteristic axillary odors in males consist of C6-C11, saturated, unsaturated and branched acids, with (E)-3-methyl-2-hexenoic acid (3M2H) being the major compound in this mixture. The 3M2H appears to be carried to the skin surface bound to two proteins in the axillary secretions. Data reported here show that the same mixture of odorous compounds is found in female axillary secretions, with several minor qualitative differences. Separation of the female apocrine secretions into aqueous and organic soluble fractions demonstrated that 3M2H, and several other members of the acids in the characteristic odor, are released by hydrolysis with base. Electrophoretic separation of the proteins found in the aqueous phase of female apocrine secretions revealed a pattern identical to that seen in males. The qualitative similarity of the acidic constituents making up the characteristic axillary odors of both females and males as well as the proteins present in the aqueous phase suggest a similar origin for axillary odors in both sexes.

Cross-adaptation of sweaty-smelling 3-methyl-2-hexenoic acid by a structurally-similar, pleasant-smelling odorant.

Cross-adaptation has been interpreted as a measure of the degree to which odors share common sensory channels. How structural similarity, in the absence of perceptual similarity, influences cross-adaptation is unknown. The present study assessed cross-adaptation by structurally similar, but perceptually different, odorants. Magnitude estimates for a 10:1 mixture of (E)- and (Z)-3-methyl-2-hexenoic acid (3M2H), a principal component of human underarm odor, decreased following adaptation to a mixture of (E)- and (Z)-ethyl esters of 3M2H (EE3M2H), which possess a pleasant, fruity odor. Cross-adaptation was asymmetric; adaptation to 3M2H did not significantly affect the perceived intensity of EE3M2H. By contrast, there was no significant cross-adaptation between 3M2H and the fruity-smelling ethyl esters of its homologues, 3-methyl-2-octenoic acid (EE3M20) and 3-methyl-2-pentenoic acid (EE3M2P). Similarity ratings revealed no differences among the three ethyl esters in their perceptual similarity to 3M2H (i.e. all were rated equally dissimilar to 3M2H). Molecular modeling studies revealed no difference in the charge distribution of these molecules. Rather, differences in the shape and size of the hydrophobic part of the molecule may determine the extent of cross-adaptation. These results demonstrate that structurally-similar, yet perceptually-distinct, odorants may cross-adapt and suggest that the extent of cross-adaptation may be affected by the degree of structural, as well as perceptual, similarity.

Proteinaceous precursors of human axillary odor: isolation of two novel odor-binding proteins.

The characteristic odor which arises in the human axillary region consists of volatile C6-C11 acids with the most abundant being (E)-3-methyl-2-hexenoic acid (E-3M2H). This acid, as well as several other components of the characteristic axillary odor, can be liberated from the odorless, aqueous soluble components of apocrine secretion by either saponification or bacteriolysis. It is therefore likely that a major characteristic odor is being carried to the skin surface bound to a water soluble precursor where it is liberated by axillary bacteria. The individual proteins found in apocrine secretions were separated, isolated and hydrolyzed with the resultant hydrolyzates analyzed by gas chromatography/mass spectrometry. These studies demonstrated that 3M2H was liberated from 2 proteins with apparent molecular mass of 26 and 45 kilodaltons: Apocrine Secretion Odor-Binding Protein 1 and 2, respectively (ASOB1 and ASOB2). Antisera to these proteins were prepared and used to examine a variety of other body fluids. Several fluids contained an immunoreactive protein with the same electropheretic migration pattern as the 45 KDa protein. Three of these body fluids (tears, nasal secretions and saliva) were separated into aqueous and organic soluble fractions and hydrolyzed to demonstrate that 3M2H could be liberated from the aqueous soluble materials. These results suggest interesting parallels between non-human mammalian odors used as chemical signals and human axillary odor. Previous studies have suggested the axillae as a source of human primer-type pheromones; consequently, if the odors which characterize the underarm are responsible for the pheromonal activity, then the chemistry involved may be similar to that in other mammalian chemical communication systems where proteins act as carriers of one or more chemical signals.

An investigation of human apocrine gland secretion for axillary odor precursors.

Recently completed studies from our laboratories have demonstrated that the characteristic human male axillary odors consist of C6 to C11 normal, branched, and unsaturated aliphatic acids, with (E)-3-methyl-2-hexenoic acid being the most abundant. To investigate the mechanism by which the odor is formed, it is necessary to determine the nature of the odorless precursor(s) found in the apocrine secretion which is converted by the cutaneous microorganisms to the characteristic axillary odor. Pooled apocrine secretion was obtained from several male volunteers by intracutaneous injection of epinephrine. Partitioning this secretion into aqueous and organic soluble fractions was followed by hydrolysis of each fraction with NaOH or incubation with axillary microorganisms (cutaneous lipophilic corynebacterium). Analysis by gas chromatography/mass spectrometry (GC/MS) revealed the presence of (E)- and (Z)-3-methyl-2-hexenoic acid in the aqueous phase hydrolysate and aqueous phase incubated with bacteria; however, only a trace amount was seen in the resultant organic phase mixtures. These results suggest that a water-soluble precursor(s) is converted by the axillary flora to the characteristic axillary odors.

Analysis of characteristic odors from human male axillae.

A number of studies concerning the analysis of axillary odors have assumed that the characteristic odor produced in the axillae is due to volatile steroids and isovaleric acid. Organoleptic evaluation of Chromatographic eluants from axillary extracts was employed to isolate the region in the chromatogram where the characteristic odor eluted. The odor of the dissolved eluant was eliminated when it was treated with base, suggesting that acids make up the characteristic axillary odor. Subsequent extraction of the pH-adjusted axillary extract in conjunction with organoleptic evaluation of the Chromatographic eluant, preparative gas chromatography, and analysis by GC-MS as well as GC-FTIR showed the presence of a number of C6 to C11 straight-chain, branched, and unsaturated acids as important contributors to the axillary odor. The major odor component is (E)-3-methyl-2-hexenoic acid. Three homologous series of minor components are also important odor contributors; these consist of the terminally unsaturated acids, the 2-methyl-C6 to -C10 acids and the 4-ethyl-C5 to -C11 acids. These types of acids have not been reported previously as components of the human axillary secretions and have not been proposed previously as part of the principal odor components in this area.

Extreme sensitivity of grandisal to acids.

Attempted purification of synthetic racemic grandisal1 by silica gel chromatography resulted in severe decomposition. The nature of this reaction was studied on silica gel and in an ether solution ofp-toluenesulfonic acid. The same products resulted from both reaction systems, although in different ratios. Five racemic, rearrangement products were isolated by preparative GC and identified as follows: (1RS, 3SR, 6RS)-1-methyl-5-methylenebicyclo[4.2.0]octan-3-ol (4); (1RS, 3RS, 6RS)-1-methyl-5-methylenebicyclo[4.2.0]octan-3-ol (5); (1RS,3RS,6RS)-1,5-dimethylbicyclo[4.2.0]oct-4-en-3-ol (6); (1RS,3SR,6RS)-1,5-dimethylbicyclo[4.2.0]oct-4-en-3-ol(7); and 3-methyl-7-methylenecyclooct-3-en-l-ol (8). The stereochemical assignments are based on our proposed mechanism, which also accounts for all products observed. The racemic bicyclic enone (3) was a by-product of grandisol (2) oxidation.