Juvenile Hormone Esterase Activity Research Articles

Direct and correlated responses to selection on JHE activity in adult and juvenile Gryllus assimilis: implications for stage-specific evolution of insect endocrine traits

Two-way selection on the activity of the endocrine regulator, juvenile hormone esterase (JHE), in adults of the cricket, Gryllus assimilis, resulted in a realized JHE heritability of 0.059±0.001. This heritability was significantly lower than the realized JHE heritability measured previously during selection on the last juvenile stadium (0.26±0.04). We observed strong correlated responses to selection on JHE activity during different periods of adulthood but very weak correlated responses in the last juvenile stadium. The additive genetic correlation between JHE activities in adults and juveniles, measured from the two pairs of correlated and direct responses obtained from the present adult and the previous juvenile selection studies, did not differ significantly from zero. Lines from the earlier juvenile selection study, reassayed for correlated responses after an additional five generations of selection, exhibited only weak correlated responses for JHE activity in adult and penultimate stages. Results from the present adult and the previous juvenile selection studies provide a consistent picture of strong within-stage JHE correlated responses in either adult or juvenile stages. By contrast, only weak JHE correlated responses occur in contiguous developmental stages, irrespective of whether the stages are physiologically or morphologically similar or dissimilar, or whether JHE activity was selected before or after the stage in which the correlated responses were measured. The regulation of a particular life cycle stage by JHE (juvenile development) can be modified by selection without necessarily altering its regulatory role in other stages (adult reproduction).

Metamorphosis of the red flour beetle,Tribolium freemani Hinton (Coleoptera: Tenebrionidae): Alteration of octopamine content modulates activity of juvenile-hormone esterase, ecdysteroid level, and pupation

Under crowded conditions, Tribolium freemani larvae exhibited a delay in the increase of octopamine (OA) content, activity of juvenile-hormone esterase (JHE), and ecdysteroid content, leading to a delay in pupation compared to the larvae under isolated conditions. Under crowded conditions, a peak OA content appeared at days 2–4, followed by a peak of JHE activity at day 7, the second OA peak at day 9, and an ecdysteroid peak at day 11 of the instar. Optical stress, on the other hand, caused an increase in OA and ecdysteroid contents, leading to an acceleration of pupation compared to controls. Whole-body OA content reached its maximum 3 days before pupation and the ecdysteroid level 2 days later in larvae isolated, crowded, or optically stressed. The OA content, JHE activity, and ecdysteroid level showed a similar pattern after pupation till adult emergence both in crowded and uncrowded animals: peaks of OA content and JHE activity were observed at pupation, followed by the highest peak of ecdysone 4 days later (2 days before emergence). The ecdysteroid levels were higher in the crowded larvae reared under 24 h light conditions or treated with OA agonists than those in control larvae kept in the dark. Hence, isolation and optical stress increase OA content followed by JHE activity and ecdysteroid titer, leading to changes in metamorphosis program. Some OA agonists actually had the same effect as isolation and optical stress did, suggesting that OA is a causative agent in pupation programming of T. Freemani by inducing an increase in JHE activity, thus decreasing JH titer followed by an increase in ecdysteroid level and delayed pupation. Arch. Insect Biochem. Physiol. 37:34–46, 1998. © 1998 Wiley-Liss, Inc.

Coevolution of traits determining migratory tendency: correlated response of a critical enzyme, juvenile hormone esterase, to selection on wing morphology

AbstractMigratory tendency in insects is a complex trait, composed of a suite of correlated behavioural, physiological, morphological and life history traits. We investigate the genetic and physiological basis of the coevolution of this suite of traits using laboratory lines of the wing dimorphic cricket, Gryllus firmus, selected for increasing and decreasing incidence of macroptery. Selection on wing morphology has produced strong direct responses in proportion macropterous as well as correlated (indirect) responses in wing muscle histolysis, flight propensity and fecundity. We investigate the hypothesis that these responses have been mediated by changes in the metabolism of juvenile hormone (JH) during the final nymphal stadium (the critical period for wing morph determination). Previous studies of Gryllus sp. have established that JH titre in this period is determined primarily by the activity of the degradative enzyme, juvenile hormone esterase (JHE). Assays of JHE activity in the final nymphal stadium of the replicated control and selected lines demonstrate highly significant differences in both mean activity and the probability of macroptery for a given level of activity (i.e., the threshold activity required to induce wing formation). These correlated responses in JH metabolism support the general hypothesis that the correlations among traits determining migratory tendency result at least in part from the common influence of JH during the final nymphal stadium. We discuss these results in the context of the quantitative genetic model for the evolution of polygenic, dichotomous traits (the threshold model), and present four general predictions concerning the coevolution of traits associated with ecological (i.e., trophic, life history, behavioural) dimorphisms.

Characterization and temporal aspects of haemolymph juvenile hormone esterase in adult cockroach, Periplaneta americana

Daily variations in the in vitro haemolymph juvenile hormone esterase activity (hJHE) of adult male and female Periplaneta americana were monitored over a 2 week period from the time of adult emergence and throughout the first reproductive cycle of the adult female. Kinetic analysis of hJHE from females indicated an apparent K m JH III of 5.59±1.75 μ m ( V max=140 pmol JH III hydrolysed h −1 per μl haemolymph). In females the mean rate of JH III metabolism in diluted haemolymph shortly after emergence was 27.5±1.5 pmol h −1 μl −1 ( n=16) and remained relatively low (16–32 pmol h −1 μl −1) over much of early adult development. Activity remained at this level during the first two days of the 4 day reproductive cycle, but showed a much increased broad peak of activity (74–93 pmol h −1 μl −1) at 60–72 h post-extrusion. This peak lags behind the whole body JH titre peak, which could suggest that elevated levels of JH III may bring about the induction of JH esterase(s). A different pattern of JHE activity was observed in adult males. hJHE rates in males at emergence were almost twice as high (81.5±15.8 pmol h −1 μl −1, n=16) as those found in females at this time, but thereafter showed a downturn to moderate levels (44–68 pmol h −1 μl −1) that were maintained for the remainder of the study. Rapid (FPLC) DEAE–sepharose ion exchange chromatography, ultrafiltration and fast-flow superose gel filtration chromatography were employed to achieve an efficient partial purification (166-fold) of the hJHE from cell-free plasma of reproductively active female P. americana 48–72 h post-ootheca extrusion. Gel filtration and SDS–polyacrylamide gel electrophoresis (PAGE) revealed an enzyme having apparent molecular mass of between 60 and 70 kDa, whilst non-denaturing PAGE and iso-electrofocusing resolved a single acidic enzyme peak with a pI of 4.9.

Purification and characterization of juvenile hormone esterase from hemolymph of the Colorado potato beetle

In the Colorado potato beetle (Leptinotarsa decemlineata), low juvenile hormone (JH) titers are necessary to initiate metamorphosis and diapause. Low JH titers coincide with high activities of JH esterase, which occur mainly in the hemolymph. The specific activity of JH esterase appeared to be highest in the last larval instar, at day 3 after the molt, and reached a value of 13.5 nmol/min/mg. JH esterase was purified from hemolymph collected at this stage be a sequence of separation systems, including preparative nondenaturing PAGE, isoelectric focusing, and SDS-PAGE. The enzyme had a molecular weight of 120,000 and was composed of two subunits with molecular weights of 57,000, which were not linked by disulphide bridges. Isoelectric focusing revealed two forms of the enzyme with isoelectric points of 5.5 and 5.6. The Km and kcat of the purified enzyme were determined. The major form with pl 5.6 had a Km of 1.4 x 10(-6) M and a kcat of 0.9 s-1 and the minor form with pl 5.5 had a Km of 2.2 x 10(-6) M and a kcat of 1.9 s-1. The quaternary structure of L. decemlineata JH esterases, as differs from JH esterases in other species, which are monomers.

Vermunt AMW, Vermeesch AMG, de Kort CAD (1997): Purification and characterization of juvenile hormone esterase hemolymph of the Colorado potato beetle. Arch Insect Biochem Physiol 35:261-277.

The last sentence in the abstract was printed incorrectly. The correct sentence is printed below in the abstract. The authors regret the error. In the Colorado potato beetle (Leptinotarsa decemlineata), low juvenile hormone (JH) titers are necessary to initiate metamorphosis and diapause. Low JH titers coincide with high activities of JH esterase, which occur mainly in the hemolymph. The specific activity of JH esterase appeared to be highest in the last larval instar, at day 3 after the moult, and reached a value of 13.5 nmol/min/mg. JH esterase was purified from hemolymph collected at this stage by a sequence of separation systems including preparative nondenaturing PAGE, isoelectric focusing and SDS-PAGE. The enzyme was demonstrated to have a molecular weight of 120,000 and was composed of two subunits with molecular weight of 57,000, which were not linked by disulphide bridges. Isoelectric focusing revealed two forms of the enzyme with isoelectric points of 5.5 and 5.6. The Km and kcat of the purified enzyme were determined. The major form with pI 5.6 had a Km of 1.4 × 10–6M and a kcat of 0.9 s–1 and the minor form with pI 5.5 had a Km of 2.2 × 10–6M and a kcat 1.9 s–1. The quaternary structure of L. Decemlineata JH esterase as a dimer, differs from JH esterases in other species, which are monomers.

Apparent inhibition of in vitro juvenile hormone biosynthesis by the corpus cardiacum of adult crickets (Gryllus bimaculatus andAcheta domesticus) is due to juvenile hormone esterase

When measuring the in vitro JH III-biosynthesis by corpora allata (CA) from adult female crickets in the presence of corpora cardiaca (CC), the amount of JH III in the medium decreased in a dose dependent manner. The CC of a 4-day-old female Gryllus bimaculatus contain 42 pmol.pair CC-1 Grb-AKH, 0.62 pmol.pair CC-1 octopamine, and a JH-esterase activity of 9.8 pmol JH.h-1.pair CC-1. Comparable values for Acheta domesticus are 21 pmol.pair CC-1 Grb-AKH, 0.53 pmol.pair CC-1 octopamine, and 6.5 pmolJH.h-1.pair CC-1 of JH-esterase activity. Even if the entire octopamine content of the CC were released into the medium, the concentration would be below the 10(-5) M threshold for octopamine inhibition of JH synthesis. An in vitro AKH inhibition of JH III synthesis was observed, but only at a relatively high concentration (10(-5) M). If the entire AKH content (10(-6) M) of the CC were released into the medium, the AKH concentration would approach JH synthesis inhibiting levels. However, the rate of release of AKH in vitro was very low, and, therefore, AKH from the CC could not affect JH synthesis. In contrast, a specific JH-esterase, released by isolated CC into the medium, was sufficiently high in both cricket species to account for the observed decrease in JH III present. OTFP-sulfone (10(-5) M) restored apparent JH synthesis of the CA to the control level. There was no reduction in the amount of JH released when CA were incubated with heat treated CC. The CA themselves contained almost no JH-esterase activity.

Characterization of the esterase isozymes ofIps typographus (coleoptera, scolytidae)

Four esterase isozymes hydrolyzing α-naphthyl acetate (α-NA) were detected screening whole body homogenates of larvae and adults of Ips typographus by electrophoresis. Two of the four isozymes (isozymes 3 and 4) were not detected by α-NA staining in the pupal stage, but topical application of juvenile hormone III (JH III) on the pupa induced these isozymes. The JH esterase (JHE) activity on the gel was associated with the proteins of isozyme 2. The compounds OTFP, PTFP, and DFP inhibited this catalytic activity of isozyme 2 on the gel at low concentrations, whereas the proteins of isozyme 3 and 4 were affected only at higher concentrations. A quantitative developmental study was performed to characterize which of the esterases hydrolyzed JH III, using a putative surrogate substrate for JH (HEXTAT) and α-NA. The I50 of several esterase inhibitors and the JH metabolites were also defined. All findings supported the results that a protein associated with isozyme 2 is catabolizing JH and that isozymes 3 and 4 are the main contributors to the general esterase activity on α-NA. The JHE from Tenebrio molitor was purified by affinity chromatography. Although the recovery was low, an analytical isoelectric focusing gel showed that the JHE activity of the purified enzyme. T. molitor cochromatographed at the same pl as the JHE activity of I. typographus. Arch. Insect Biochem. Physiol. 34:203–221, 1997. © 1997 Wiley-Liss, Inc.

Inhibitory effects of parasitism by the gregarious endoparasitoidCotesia congregata on host testicular development

Cotesia congregata is a gregarious larval endoparasitoid of the tobacco hornworm, Manduca sexta. Parasitized larvae exhibit a variety of physiological and developmental aberrations, the most obvious of which is the induction of developmental arrest characterized by the absence of wandering behavior and suppression of pupation. This arrest appears attributable to continued maintenance of an elevated titer of juvenile hormone and reduced levels of hemolymph juvenile hormone esterase activity. Injection of the wasp's polydnavirus into nonparasitized larvae also causes arrest and the larvae eventually form larval-pupal intermediates instead of normal pupae, indicating the virus may be partially responsible. Aside from causing arrested host development, parasitism also inhibits the normal development and differentiation of testes in male host larvae, so that the testes atrophy instead of growing synchronously with other larval tissues. Here we report that parasitism has pronounced disruptive cytological effects on the developing reproductive organs of male hosts, in addition to causing them to atrophy. Parasitism results in a reduction in testicular volume attributable to a reduction in the number of developing germ cells. Microscopy revealed that the structural integrity of the sheaths surrounding the testicular follicles also is disrupted, so that the tissues appear grossly abnormal compared to those of nonparasitized larvae. Intrahemocoelic injection of purified C. congregata polydnavirus in combination with venom into nonparasitized fourth instar larvae, or topical application of 100 μg of methoprene to fourth instar larvae, also alters sheath integrity and reduces the numbers of developing germ cells, but not to the same degree as the pattern observed in truly parasitized hosts. The occurrence of cell death in the male gonad was documented using the vital dyes acridine orange and ethidium bromide. Arch. Insect Biochem. Physiol. 36:95–114, 1997. © 1997 Wiley-Liss, Inc.

Biochemical characterization of juvenile hormone esterases from lines selected for high or low enzyme activity in Gryllus assimilis.

In a previous study, activity of the insect endocrine regulator juvenile hormone esterase (JHE), in the cricket Gryllus assimilis, was subjected to bidirectional selection. This resulted in three pairs of high- and low-selected lines, each of which differed by 3.5-fold in JHE activity. In the present study, juvenile hormone esterases from these lines were characterized with respect to the Michaelis constant (K(m)), thermostability, and inhibition. None of three high-selected JHEs differed from its respective low-selected JHE in the Michaelis constant (K(m)) for juvenile hormone. Similarly, the high-selected JHEs did not differ from the low selected JHEs in thermostability or inhibition by either of two general esterase inhibitors (DFP, eserine) or a "JHE-specific" inhibitor (OTFP). Thus no evidence was obtained to suggest that the response to selection was due to allozymes or isozymes with altered kinetic or stability properties. Kinetic and stability properties were also very similar for the JHEs from the three high-selected or the three low-selected lines. Finally, none of the thermostability or inhibition profiles for any of the six JHEs exhibited sharp discontinuities, thus providing no evidence for the existence of multiple isozymes. The available evidence points to genetically variable regulators which affect the synthesis, degradation, or tissue distribution of JHE as being responsible for the divergence in JHE activity between the selected lines.

Role of the corpora allata and juvenile hormone in the control of imaginal diapause and reproduction in three species of locusts

To understand the hormonal regulation of imaginal diapause and ovarian development in three species of locusts, Nomadacris succincta, Nomadacris japonica and Locusta migratoria, juvenile hormone (JH) biosynthesis by the corpora allata (CA) in vitro and JH esterase activity in the hemolymph were measured. The two species of Nomadacris exhibited a positive correlation between oocyte growth and JH biosynthesis by CA in vitro, although the correlation was significant only in N. succincta. In contrast, L. migratoria showed a negative correlation, indicating a higher rate of JH synthesis associated with more suppressed ovarian development. In this species, however, the hemolymph JH titer was higher in reproductively active females than in sexually immature females, indicating a positive correlation between the hemolymph JH titer and ovarian development. The levels and temporal pattern of variation in mean hemolymph JH esterase activity were rather similar between reproductively active and inactive females in L. migratoria. It is thus unlikely that the hemolymph JH esterase plays an important role in the regulation of the hemolymph JH titers in this species. Topical application of 100 μg of methoprene stimulated ovarian development significantly in L. migratoria, whereas 450 μg failed to induce ovarian development or vitellogenesis in sexually immature females of N. succincta and N. japonica. Besides JH, there appear to be other factors present that are involved in the control of the termination of diapause in the two Nomadacris species.

The role of juvenile hormone and juvenile hormone esterase in wing morph determination in Modicogryllus confirmatus

The role of juvenile hormone (JH) and juvenile hormone esterase (JHE) in regulating wing morph determination was studied in the cricket Modicogryllus confirmatus. JHE activities were significantly higher in nascent long-winged (LW) vs short-winged (SW) crickets during the latter half but not during the first half of the last stadium. The magnitude and direction of the activity differences were similar to those previously documented between wing morphs of the cricket, Gryllus rubens. In contrast, activities of general esterase, an enzyme or group of enzymes with no demonstrated role in regulating the JH titer in insects, showed no or only minor differences between morphs. The magnitude and direction of the JHE activity variation is consistent with a regulatory role for this enzyme in some aspect of wing dimorphism. However, the timing of the differences (exclusively during the last half of the last stadium) argue against a role in regulating wing length development per se. Single or multiple applications of juvenile hormone-III to nascent LW individuals during the first few days of the last stadium significantly redirected development from long to short wings. Multiple applications of acetone, by itself, also increased the production of short-winged adults. For most treatments, all individuals with shortened wings also had undeveloped flight muscles. These data suggest that JH may play a role in wing morph determination in M. confirmatus but that it affects a different aspect of the polymorphism from JHE.

A comparative analysis of juvenile hormone metabolyzing enzymes in two species of Drosophila during development

The course of changes in the activities of enzymes degrading juvenile hormone (JH), epoxyde hydrolase (JHEH) and JH-esterase (JHE) was studied in two lines of Drosophila virilis (101 and 147) and in two lines of D. melanogaster (Canton-S and 921283). It was established for D. virilis that changes in the JH titre during pupal-adult development is determined by the activity level of JHE rather than JHEH, while in D. melanogaster developmental changes in JH titre are related to changes in the activity level of both JHE and JHEH. In adults of D. virilis, the high level of JH-hydrolysing activity is determined by JHE and in those of D. melanogaster by JHEH. Differences in the course of changes in the JHE activity level between adults of lines 101 and 147 of D. virilis were found, and also in the JHEH activity level between adults of lines Canton S and 921283 of D. melanogaster. It was shown that attainment of a definite JHE activity level in females of lines 101 and 147 agrees well with the onset of oviposition of fertilized eggs. The possible role of JHE in reproduction of D. virilis is discussed.

Juvenile hormone esterase activity during the reproductive cycle of the ring-legged earwig

Corpora allata of the ring-legged earwig, Euborellia annulipes, produce and secrete juvenile hormone III (JH III). The primary degradation product of JH III in vitro by diluted hemolymph was juvenile hormone acid, as assessed by thin-layer and high-performance liquid chromatography. This result was confirmed by derivatization of the degradation product using diazomethane. Conversion of JH III to JH acid by E. annulipes hemolymph in vitro occurred at a constant rate for at least 4 hr. The addition of 10 −6 M O-ethyl-S-phenyl phosphoamidothiolate or, alternatively, 3-octyl thio-1,1,1-trifluoropropan-2-one inhibited hemolymph esterase activity; O,O-diisopropylphosphorofluoridate and ethanol alone had no effect on the conversion of JH III to JH acid. At 10 −4 M, each of the selected inhibitors reduced hemolymph esterase activity relative to ethanol-treated and untreated controls. JH esterase activity of diluted hemolymph was relatively high in females with basal follicles < 0.2 mm and low in those with larger basal follicles. The change in JH esterase activity of the hemolymph was not correlated with changes in hemolymph protein content; hemolymph protein content was generally 50–100 μg/μ1 and did not change significantly with either age or basal follicle length.

Parasitism by Microplitis demolitor induces alterations in the juvenile hormone titers and juvenile hormone esterase activity of its host, Pseudoplusia includens

Microplitis demolitor is a polydnavirus-carrying parasitoid that attacks the larval stage of Pseudoplusia includens and other noctuids. Parasitism or injection of wasp components like polydnavirus and teratocytes has a juvenilizing effect on P. includens development. Here we measured hemolymph juvenile hormone (JH) titers and juvenile hormone esterase activity in P. includens larvae after parasitism or injection of wasp components. Results were compared to nonparasitized larvae. During the fifth stadium, JH titers of nonparasitized larvae fluctuated between 0.08 and 0.50 ng/ml, whereas titers in parasitized larvae never fell below 2 ng/ml. P. includens larvae injected with calyx fluid plus venom or calyx fluid plus venom and teratocytes exhibited JH titers intermediate between parasitized and nonparasitized larvae. Nonparasitized larvae exhibited two peaks of JH esterase activity. The first occurred between 12 and 48 h in association with cessation of larval feeding, while the second occurred immediately before pupation. In contrast, levels of JH metabolism remained at low levels in parasitized larvae and larvae injected with calyx fluid plus venom or calyx fluid, venom and teratocytes. Only trace amounts of JH were detected in in vitro assays of teratocytes or M. demolitor larvae suggesting neither released JH into the hemolymph of parasitized larvae. Although calyx fluid plus venom and teratocytes did not elevate JH titers to the levels measured in parasitized larvae, their effects on formation of larval-pupal intermediates by P. includens were similar to those generated by exogenous application of methoprene or JH.

Juvenile hormone metabolism in the ovary, gut, head and carcass after blood feeding in the southern house mosquito, Culex quinquefasciatus

The regulation of JH epoxide hydrolase, JH esterase and 1-naphthyl acetate (NA) esterase activity was studied in ovary, gut head and carcass after blood feeding in Culex quinquefasciatus. The combined tissues had the greatest JH epoxide hydrolase and JH esterase activity from 24–36 hr after a blood meal. JH epoxide hydrolase activity per female was 2.1-, 1.8- and 1.1-times greater than the JH esterase activity at 24, 36, and 48 hr after blood feeding, respectively. JH epoxide hydrolase activity per unit protein was also the major route of primary JH metabolism at most time points examined, and peak JH epoxide hydrolase activity per unit protein in the gut, head and carcass was approximately 2-times the highest JH esterase activity per unit protein in corresponding tissues and 4-times the peak JH esterase activity in the ovary. The differential expression of JH epoxide hydrolase versus JH esterase in specific tissues and between tissues suggested that regulation of JH metabolism is tissue specific. Two isoelectric forms of JH esterase were found. The juvenoid, (RS)-methoprene, interfered with the regulation of JH esterase activity, but failed to change the activity levels of JH epoxide hydrolase and 1-NA esterase.

In vivo and in vitro-tissue specific metabolism of juvenile hormone during the last stadium of the cabbage looper, Trichoplusia ni

In vitro metabolism of racemic JH III (5 μM) was measured in fat body, midgut and integument homogenate during the last stadium of the cabbage looper, Trichoplusia ni. The JH esterase activity per mg protein peaked in these tissues in prewandering larvae on day 2 and was elevated in the fat body only in prepupae (on day 4). The JH epoxide hydrolase activity peaked on day 2 in midgut and on day 3 (in wandering larvae) in fat body and integument. No differences were noted in the overall JH III metabolism in vitro per insect between wandering (day 3) larvae and prepupae (day 4) and in the in vivo metabolism of 10R11S-JH II when injected in oil and buffer or when topically applied at physiological concentrations into these same stages. Regardless of the method of introduction of JH II, JH diol was produced in both wandering larvae and prepupae. JH acid and JH acid, diol were also produced but the predominant product was a water soluble metabolite. The preferred substrate for JH epoxide hydrolase at physiological concentrations was JH II as opposed to JH II acid. Approximately half of the JH II after injection into wandering larvae was associated with the alimentary canal and carcass. The metabolites of JH II were evenly distributed. The importance of JH epoxide hydrolase in JH metabolism in last stadium Lepidoptera is discussed.

Artificial selection on JHE activity inGryllus assimilis: Nature of activity differences between lines and effect on JH binding and metabolism

Genetic lines of the cricket Gryllus assimilis selected for elevated vs. decreased activity of hemolymph juvenile hormone esterase (JHE) exhibited a 6.8-fold difference in enzyme activity by the seventh generation of selection. This documents that hemolymph JHE activity has the capability for rapid evolutionary change. This is the only insect endocrine trait for which such data are currently available. The difference in hemolymph JHE activity between the lines was due, to an equivalent degree, to variation in whole-cricket enzyme activity and allocation of JHE activity to the hemolymph compartment. No differences in kinetic or thermostability characteristics were observed between JHEs from the high- vs. low-selected lines. This suggests that the variation in JHE activity between the lines resulted from selection of variable regulatory genetic factors affecting the synthesis, degradation, or activation of enzyme activity. JHE and JH-binding activity in the hemolymph are genetically correlated, possibly due to co-regulation by the same genetic factors. Finally, in vivo JH degradation was significantly elevated in lines selected for elevated JHE activity. This documents that evolutionary changes in JHE activity alter in vivo JH metabolism. © 1996 Wiley-Liss, Inc.

Artificial selection on JHE activity in Gryllus assimilis: Nature of activity differences between lines and effect on JH binding and metabolism

Genetic lines of the cricket Gryllus assimilis selected for elevated vs. decreased activity of hemolymph juvenile hormone esterase (JHE) exhibited a 6.8-fold difference in enzyme activity by the seventh generation of selection. This documents that hemolymph JHE activity has the capability for rapid evolutionary change. This is the only insect endocrine trait for which such data are currently available. The difference in hemolymph JHE activity between the lines was due, to an equivalent degree, to variation in whole-cricket enzyme activity and allocation of JHE activity to the hemolymph compartment. No differences in kinetic or thermostability characteristics were observed between JHEs from the high- vs. low-selected lines. This suggests that the variation in JHE activity between the lines resulted from selection of variable regulatory genetic factors affecting the synthesis, degradation, or activation of enzyme activity. JHE and JH-binding activity in the hemolymph are genetically correlated, possibly due to co-regulation by the same genetic factors. Finally, in vivo JH degradation was significantly elevated in lines selected for elevated JHE activity. This documents that evolutionary changes in JHE activity alter in vivo JH metabolism. © 1996 Wiley-Liss, Inc.

Effect of mating on plasma juvenile hormone esterase activity in females ofChoristoneura fumiferana andC. rosaceana

We measured juvenile hormone esterase (JHE) activity in the plasma of virgin and mated Choristoneura fumiferana and C. rosaceana female moths. In these two species, JH III acid was the only measurable product of in vitro JH III degradation in the plasma. Rates of JH III ester hydrolysis were generally higher in C. rosaceana than in C. fumiferana, but followed a similar pattern in both species, with high activity measured on day 7 of the pupal stage, the lowest activity measured at emergence, and a subsequent increase observed between days 0 and 1. Mating on day 0, in both species, brought about a significant increase in JHE activity on day 1, relative to virgins. On days 3 and 5, rates of JH degradation did not differ between virgin and mated females. The mating-induced increase in JHE activity on day 1 was not the result of a decrease in blood volume in mated females relative to virgins. Fluctuations in JHE activity did not appear to depend on changes in plasma protein concentration. In both species, topical application of JH I or methoprene, on the day of emergence, resulted in dose- and time-dependent increases in JHE activity relative to controls. © 1996 Wiley-Liss, Inc.