Biosynthetic maturation of the corpus allatum of the female adult medfly,Ceratitis capitata,and its putative control

The major juvenile hormone (JH) homolog synthesized in vitro by the adult female Medfly (Ceratitis capitata) corpus allatum (CA) is JHB(3), with JH-III the minor homolog. Methyl-incorporation in vitro in post-eclosion virgin females is age-dependent. Basal activity occurs during the first four days post-eclosion and increases significantly thereafter, peaking at five days. Biosynthetic maturation of the mated female CA is delayed by one day and reduced considerably. The delayed response may be due to direct cerebral or neural inhibition. Synthetic Drosophila melanogaster sex peptide depresses JH biosynthesis by the Medfly female CA in vitro. Male-derived accessory gland peptides of the Medfly are transferred to the female during mating and a Medfly SP-analog may be responsible for down-regulation of JH synthesis by the CA in mated Medfly females. Mevinolin, an inhibitor of the mevalonate pathway, significantly reduces the biosynthesis of JHB(3), while farnesoic acid, a proximate precursor of JHIII, significantly stimulates the biosynthesis of both JHB(3) and JHIII in vitro.     

Activity of the corpora allata of adult female Leucophaea maderae: effects of mating and feeding

Juvenile hormone III biosynthesis by corpora allata of adult female Leucophaea maderae was measured by an in vitro radiochemical assay. In fed females, JH III synthesis increases more than 20-fold after mating to a peak of 55 pmol/pair/h on day 9 and then rapidly declines. This increase in JH III synthesis concomitant with rapid oocyte growth in mated females is not observed in virgin females. The corpora allata from starved, virgin females appear to be inactive. The addition of 150 microM 2E,6E-farnesol (a) JH III precursor) to the incubation medium stimulates the corpora allata from starved, virgin females less than the corpora allata from starved, mated females. Both feeding and mating are necessary for the expression of a normal cycle of JH III synthesis in this cockroach.     

Methyl palmitate: a novel product of the Medfly (Ceratitis capitata) corpus allatum

The corpus allatum (CA) of adult female Ceratitis capitata produces methyl palmitate (MP) in vitro, in addition to JHB₃ and JH III. Biosynthesized MP migrates on TLC and co-elutes from RP-18 HPLC with synthetic MP. Its identity is verified herein by GCMS. MP production is up-regulated twofold by mevastatin, an inhibitor of mevalonic acid-dependent isoprene biosynthesis. Fosmidomycin, an inhibitor of mevalonic acid-independent isoprene synthesis in graminaceous plants, up-regulates MP synthesis by about fourfold. However, it does not depress JHB₃ biosynthesis concurrently. This suggests that the initial enzyme(s) in the conversion of 1-deoxy-xylulose 5-phosphate to isoprene is presumably present in C. capitata, but is inhibited by fosmidomycin, and this inhibition diverts precursors to MP synthesis. Phytol, an acyclic diterpene, might be suppressing isoprene biosynthesis by CA, thereby resulting in a fourfold increase in the MP biosynthesis. Linolenic acid is an end-product and its presence in incubation media up-regulates MP biosynthesis by twofold, presumably due to the feedback diversion to biosynthesis of C_16:0 and its methyl ester. Biosynthesis of MP is markedly depressed after mating, while otherwise maintained at significantly higher levels in virgin females. MP biosynthesis is significantly reduced in virgin females by direct axonal control but is less consistent after mating.     

Juvenile hormone titre and egg production in Tenebrio molitor infected by Hymenolepis diminuta: effect of male and/or female infection,male age and mating

Infection of Tenebrio molitor with Hymenolepis diminuta induces curtailment of female fertility. We examined ovulation and oviposition, and associated titres of juvenile hormone (JH), in relation to parasitism and mating. Oviposition was significantly increased in infected mated and virgin beetles by days 6 and 9 post-emergence. Ovulation was not changed by infection; by the end of the 18-day experiment, the total number of laid eggs was not significantly altered. On day 6, JH levels were significantly higher in virgin infected insects, compared to non-infected controls (236+/-37.7 and 107+/-9.62 pg/g wet weight). Oviposition increased after mating, but total eggs ovulated remained the same. JH levels were higher in mated females on days 12 and 18 post-emergence, for infected and control insects. Previous studies suggested that male reproductive potential might rise following infection, because uninfected females lay more eggs when mated to infected males. We tested whether this caused an increase in female JH. Males were mated on days 5 or 12, when significant changes in their reproductive physiology begin to be observed, and are maximal, respectively. However, male age was of greater significance in promoting JH levels in females (p=0.001), than infection status of either partner (p=0.33).     

Methyl palmitate: a novel product of the Medfly (Ceratitis capitata) corpus allatum

The corpus allatum (CA) of adult female Ceratitis capitata produces methyl palmitate (MP) in vitro, in addition to JHB₃ and JH III. Biosynthesized MP migrates on TLC and co-elutes from RP-18 HPLC with synthetic MP. Its identity is verified herein by GCMS. MP production is up-regulated twofold by mevastatin, an inhibitor of mevalonic acid-dependent isoprene biosynthesis. Fosmidomycin, an inhibitor of mevalonic acid-independent isoprene synthesis in graminaceous plants, up-regulates MP synthesis by about fourfold. However, it does not depress JHB₃ biosynthesis concurrently. This suggests that the initial enzyme(s) in the conversion of 1-deoxy-xylulose 5-phosphate to isoprene is presumably present in C. capitata, but is inhibited by fosmidomycin, and this inhibition diverts precursors to MP synthesis. Phytol, an acyclic diterpene, might be suppressing isoprene biosynthesis by CA, thereby resulting in a fourfold increase in the MP biosynthesis. Linolenic acid is an end-product and its presence in incubation media up-regulates MP biosynthesis by twofold, presumably due to the feedback diversion to biosynthesis of C_16:0 and its methyl ester. Biosynthesis of MP is markedly depressed after mating, while otherwise maintained at significantly higher levels in virgin females. MP biosynthesis is significantly reduced in virgin females by direct axonal control but is less consistent after mating.     

Activity of the corpora allata of adult female Aedes aegypti: effects of mating and feeding

The synthesis of juvenile hormone III (JH III) by the isolated corpora allata (CA) of Aedes aegypti adult female was studied using an in vitro radiochemical assay. We dissected the corpora allata-corpora cardiaca (CA-CC) complex attached to a piece of aorta. The complex was left connected to the intact head capsule to facilitate the visualization and transfer of the glands. A linear increase in the cumulative amount of biosynthesized JH III was found for at least the first 6 h of incubation; approximately 45% of the synthesized JH III was present in the medium. There was a dependence of JH III synthesis on exogenous methionine supply. Using reversed phase high performance liquid chromatography two major labeled products biosynthesized by the CA were separated. They co-migrated with JH III and methyl farnesoate (MF). The identity of the biosynthesized JH III was confirmed by gas chromatography-mass spectrometry. JH III synthesis was only 2.0 fmol/pair gland/h immediately after adult emergence, but increased to 32.6 fmol/ pair gland/h 18 h later in sugar-fed females. Two days after emergence, the CA biosynthetic activity slowly started to decrease, and reached values of around 5.3 fmol/pair gland/h by one week after emergence. Synthesis of JH was similar from either sugar-fed females mated or unmated. A blood meal resulted in a decrease of JH III synthesis in CA from mated females by 12 h after feeding and from virgin females by 24 h after feeding. JH III biosynthesis remained low for at least 96 h in mated females, but was back to higher levels 72 h after feeding in virgin females. Rates of JH III biosynthesis closely reflected the hemolymph levels of JH III both after emergence and after a blood meal described by Shapiro et al. (1986). The activity of the CA in Aedes aegypti females seems to be regulated by developmental changes and nutritional signals, and to be independent of mating stimulus.     

Role of juvenile hormone esterase and epoxide hydrolase in reproduction of the cotton bollworm, Helicoverpa zea

The role of juvenile hormone (JH) esterase (JHE) and epoxide hydrolase (EH) in reproduction of the cotton bollworm, Helicoverpa zea, was investigated. Peak emergence of male and female bollworm adults occurred early in the scotophase. Female adults were added to males in a 1:2 ratio, respectively, at the beginning of the first photophase after emergence (d0). The highest oviposition rates for mated females were noted on d 2-4. The in vitro JH III esterase and JH III EH activity was measured in whole body homogenates of virgin and mated females from d0 to d8 post-emergence. Maximal JHE activity for virgin females occurred on d2 (1.09+/-0.14(+/-1 SEM) nmol of JH III degraded/min/mg protein), which was approximately twice that of mated females on the same day. The same results were observed for EH where the activity peaked on d2 at 0.053+/-0.003 as compared to 0.033+/-0.003 nmol of JH III degraded/min/mg protein, respectively. By d4, both JHE and JH EH activities declined significantly in virgin and mated females and were the same through d7. The developmental changes and effects of mating on JH degradation were similar when measured per insect. The highest levels of JHE and JH EH activity/min/mg protein in d2 virgin and mated females was found in ovaries followed by the carcass and then haemolymph; no EH activity was found in haemolymph as expected. For ovary, the JHE and JH EH activity was highest in virgin compared to mated females. The role of both enzymes in the regulation of reproduction is discussed.     

Quantification of allatostatin receptor mRNA levels in the cockroach, Diploptera punctata, using real-time PCR

The cockroach allatostatin receptor (Dippu-AstR) is a 425 amino acid G-protein coupled receptor that is related to the mammalian galanin receptor. Using relative standard curve real-time PCR analysis, changes in Dippu-AstR mRNA expression levels were examined in tissues of adult mated and virgin female Diploptera punctata. Tissues were chosen that were either known targets of allatostatin (Dippu-AST) action or sites of Dippu-AST localization. Tissues examined included brain, corpora allata (CA), gut, ovaries, testes and abdominal ganglia. Dippu-AstR was expressed in all tissues examined for 7 days after adult emergence. Juvenile hormone (JH) biosynthesis is known to peak on day 5 post-emergence in mated females. In mated females, Dippu-AstR mRNA was at the highest levels on day 6 post-emergence in brain and CA and day 2 post-emergence in midgut. Dippu-AstR expression was found to correlate with the decline in JH biosynthesis noted on day 5 post-emergence and early inhibition of feeding. Dippu-AstR mRNA expression in virgin female midgut and CA was dramatically elevated on days 6 and 7, respectively. Expression of Dippu-AstR mRNA was found to be similar in the abdominal ganglia of mated or virgin females. Ovarian Dippu-AstR expression declined to low levels by day 4. Testes exhibited maximal Dippu-AstR mRNA expression on days 4 and 7 of adult life. A role for Dippu-AST in testes of Diploptera is unknown.     

Role of juvenile hormone-esterase in mating-stimulated egg development in the moth Heliothis virescens

Juvenile hormone (JH) titer in virgin females of Heliothis virescens is significantly lower than that in mated females of the same age. The JH titer in virgin females follows a diel pattern in which it begins to increase towards the end of photophase, remains high around the onset of scotophase, and declines during scotophase. The titer reaches its lowest levels at the onset of photophase, and remains low during the first half of photophase. In mated females, the diel pattern of JH titers is not as pronounced. JH-esterase (JHE) activity in mated females is significantly lower than that of virgin females during photophase; JHE levels in the former are similar to levels seen in newly emerged females. JHE activity in mated females also exhibits a diel pattern, in which activity is low during photophase and high at the onset of scotophase. Evidence for the indirect involvement of JHE in the mating-stimulated egg development is provided by the effect of selected JHE inhibitors in inhibiting JHE activity and stimulating egg production in virgin females.     

Temporal profiles of juvenile hormone titers and egg production in virgin and mated females of Heliothis virescens (Noctuidae)

Juvenile hormones (JH) I, II, and III were monitored in hemolymph of virgin and mated females of various ages in Heliothis virescens. JH I was the predominant homologue followed by JH II, but JH II was present at a higher level in young virgin females. JH III was detectable only at a low level. In virgin females, hemolymph JH titers were low at emergence (2.2ng/ml-total amount of JH I and JH II), but increased thereafter and reached a maximum at 24h of age (53.5ng/ml). At 30h and 36h of age, JH titers dropped to a low level, but increased again in older virgin females. After mating, JH titers increased significantly. JH titers at 0h after uncoupling (137.4ng/ml) were nearly 3 times as high as those in 24-h-old virgin females. Within 6h after uncoupling, JH titers decreased slightly, but titers increased with age of mated females and reached a level of 320.2ng/ml hemolymph at 72h after uncoupling. The titer of JH I and JH II was correlated highly with total number of eggs produced (r(2)=0.70, P<0.001). Mating stimulated JH production, resulting in an increase in egg production.