Effects of juvenile hormone and 20-hydroxyecdysone on alkaline phosphatase activity in Drosophila under normal and heat stress conditions

The effect of 20-hydroxyecdysone (20E) and the juvenile hormone (JH) on the activity of the alkaline phosphatase (ALP) has been studied in young females of wild-type Drosophila virilis and Drosophila melanogaster under normal conditions and under heat stress (38 degrees C). Both 20E feeding of the flies and JH application led to a substantial rise in ALP activity. ALP activity was also measured in young females of a JH-deficient strain of D. melanogaster, apterous(56f). A decrease in the enzyme activity was observed in the mutant females as compared to wild type. A rise in JH and 20E levels was found not to prevent the response of ALP to heat stress, but to change its stress-reactivity. Mechanisms of regulation of dopamine (DA) level by gonadotropins in Drosophila are discussed.     

Juvenile hormone, 20-hydroxyecdysone and dopamine interaction in Drosophila virilis reproduction under normal and nutritional stress conditions

To elucidate the role of the juvenile hormone (JH) in the control of Drosophila reproduction under stress, JH degradation, dopamine (DA) content and reproduction were studied upon 20E treatment in Drosophila virilis females of wild type (wt) and a mutant, with increased 20E level and decreased fertility, under normal and nutritional stress conditions. 20E treatment of wt flies for 7 days results in an increase of DA content in young females, but a decrease in mature females, a decrease of JH degradation in both young and mature females, an 1-day delay in onset of oviposition and a decrease of fecundity to the level typical of mutant flies. One day of 20E treatment in 7-day-old fed and starved flies results in a small decrease of JH degradation in the fed females and a great decrease in the starved ones. Fecundity decreases in the fed flies to the levels of the starved untreated flies in both wt and mutant strains. An oviposition arrest is observed in the treated and the untreated starved, but not in the treated fed, females of both strains. The data obtained suggest ecdysone control of JH metabolism mediated via DA.     

The role of juvenile hormone in the control of reproductive function in Drosophila virilis under nutritional stress

To investigate the role of juvenile hormone (JH) in the control of Drosophila reproduction under stress, JH degradation and reproduction were studied under nutritional stress and JH treatment in Drosophila virilis females of wild type (wt) and a heat stress (hs) mutant: this mutant does not respond to heat stress by alterations in JH metabolism and has decreased JH level and fertility under normal conditions. One day of starvation results in a decrease of JH degradation, a delay in oocyte maturation, degradation of early vitellogenic egg chambers, accumulation of mature oocytes and a 24 h oviposition arrest in both wt and hs females. A fertility decrease was observed in both wt and hs females 24 h following the end of starvation. JH treatment leads to a decrease of JH degradation and an arrest of oviposition for 24 h in fed females. JH treatment prior to starvation seems to protect some oocytes from resorption: in JH-treated wt females, fertility increases rapidly following the end of starvation. The dynamics of JH degradation and fertility are similar following starvation and JH treatment. The role of JH in the accumulation of mature oocytes and the delay of oviposition under stress are discussed.     

Effects of dopamine on juvenile hormone metabolism and fitness in Drosophila virilis

The effects of dopamine (DA) on juvenile hormone (JH) metabolism and fitness (estimated as fecundity and viability levels under heat stress (38 °C)) in Drosophila virilis have been studied. An increase of DA level obtained by feeding with DA reduced fitness of wild-type (wt) flies under stress, and decreased JH degradation in young wt females while increasing it in sexually mature wt females. A decrease in DA levels resulted from 3-iodo-tyrosine treatment and caused a decrease in JH degradation in sexually mature wt and heat sensitive (hs) mutant females (DA level in hs females is twice as high in wt females). A dramatic decrease in viability under stress and fecundity under normal conditions in wt, but not hs, females was observed. 3-iodo-tyrosine treatment also reduced the number of oocytes at stages 8-14, delayed oocyte transition to stage 10 and resulted in the accumulation of mature eggs in wt females. It delayed maturation of wt, but not hs, males as well, but did not affect their fertility. This advances our understanding of the regulation of JH metabolism by DA in Drosophila and suggests a crucial role for the basal DA level in fitness.     

Ubiquitous downregulation of InR gene expression affects stress associated hormone metabolism in Drosophila females

The effect of the ubiquitous downregulation of insulin receptor (InR) gene expression on the metabolism of juvenile hormone (JH) and dopamine (DA) in young females of D. melanogaster under normal conditions and heat stress is studied. The level of JH degradation and alkaline phosphatase activity (ALP, an enzyme regulating DA synthesis) were used as indicators of JH and DA levels, respectively. We demonstrated that, under normal conditions, the ubiquitous inhibition of the InR gene expression in D. melanogaster females induced an increase in the JH degradation and ALP activity. As we have already shown, this is indicative of the decrease in the concentration of the above hormones. It was also found that the total inactivation of InR does not affect the initiation of JH and DA metabolic system response to heat stress; however, it does affect its intensity. Thus, the involvement of the insulin signaling pathway in the regulation of the JH and DA metabolism in Drosophila females was demonstrated in vivo under normal and stress conditions.     

Decrease in juvenile hormone level as a result of genetic ablation of the corpus allatum cells affects the synthesis and metabolism of stress related hormones in Drosophila

Previous studies have shown that juvenile hormone (JH) regulates dopamine (DA) and octopamine (OA) content in Drosophila, and we have shown the influence of an increase in JH level on DA and OA metabolism in young females of Drosophila virilis and Drosophila melanogaster. Here we investigate the effects of genetic ablation of a subset of cells in the Corpusallatum (CA, endocrine gland synthesizing JH) on the DA levels and activities of alkaline phosphatase (ALP), tyrosine hydroxylase (TH), DA-dependent arylalkylamine N-acetyltransferase (DAT) and tyrosine decarboxylase (TDC) in young D. melanogaster females under normal conditions and upon heat stress (38°С). We show that ablation of СА cells causes: (1) a decrease in ALP, TH and DAT activities, (2) an increase in DA level and (3) an increase in TDC activity in young females. The CA ablation was also found to modulate ALP, TH and TDC responses to heat stress. Mechanisms of regulation of DA and OA levels by JH in Drosophila females are discussed.     

Interaction of hormones in controlling reproductive function of Drosophila females under stressful conditions is genetically determined

The effect of heat stress (38 degrees C) on the content of octopamine (OA) and 20-hydroxyecdysone (20HE) was studied under normal and stressful conditions in adult flies of Drosophila virilis lines contrasting in the level of the juvenile hormone (JH). The wild-type flies (line 101) exhibited a pronounced sex dimorphism for the content of both OA and 20HE, which was substantially lower in this line than in flies of the mutant line 147. The level of both hormones increased in flies of line 101 exposed to heat stress, whereas it remained unchanged in flies of line 147 under the same conditions. The effect of heat stress on the level of JH metabolism and fertility was also studied in D. melanogaster wild-type lines and lines carrying mutations in genes responsible for OA and DA syntheses. In octopamineless females of the T beta hnM18 line and in females of the Ste line characterized by a doubled content of DA, JH degradation differed from normal: it was increased in both young and mature T beta hnM18 females, while decreased in young and increased in mature Ste flies. Fertility was substantially lower in the Ste than in the wild-type line. Flies of all of the D. melanogaster lines produced a stress response; however, in mutant lines, both fertility and stress reactivity of the systems controlling JH metabolism differed significantly from that of the wild-type lines. The role of JH, 20HE, OA, and DA interaction in regulation of Drosophila reproduction under stressful conditions is discussed.     

The ecdysoneless1 gene regulates metabolism of the juvenile hormone and dopamine in Drosophila melanogaster

The dopamine (DA) content and the level of juvenile hormone (JH) degradation were studied in females of the wild-type Canton S strain and the ecdysoneless1 (ecd1) mutant, which does not produce ecdysone at a restrictive temperature (29 degrees C). Exposure at the restrictive temperature considerably increased the JH-hydrolyzing activity and the DA content in five-day ecd1 females compared with flies of both strains growing at 19 degrees C and Canton S females exposed at 29 degrees C. In one-day ecd1 females, the level of JH degradation also increased at the restrictive temperature, but the DA content was low. The effect of ecdysone deficiency on the stress response in Drosophila melanogaster females was studied using changes in DA content and JH degradation were used as indices. The ecd1 mutation did not prevent the initiation of the stress response in females exposed at the restrictive temperature, but changed its intensity (stress reactivity). The interaction of 20-hydroxyecdysone with JH and DA in regulating Drosophila reproduction under normal conditions and in stress is discussed.     

The <Emphasis Type="Italic">ecdysoneless</Emphasis><Superscript>1</Superscript> Gene Regulates Metabolism of the Juvenile Hormone and Dopamine in <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

The dopamine (DA) content and the level of juvenile hormone (JH) degradation were studied in females of the wild-type Canton S strain and the ecdysoneless ¹ (ecd ¹) mutant, which does not produce ecdysone at a restrictive temperature (29°C). Exposure at the restrictive temperature considerably increased the JH-hydrolyzing activity and the DA content in five-day ecd ¹ females compared with flies of both strains growing at 19°C and Canton S females exposed at 29°C. In one-day ecd ¹ females, the level of JH degradation also increased at the restrictive temperature, but the DA content was low. The effect of ecdysone deficiency on the stress reaction in Drosophila melanogaster females was studied using changes in DA content and JH degradation as the reaction indicators. The ecd ¹ mutation did not prevent the initiation of the stress reaction in females exposed at the restrictive temperature, but changed its intensity (stress reactivity). The interaction of 20-hydroxyecdysone with JH and DA in regulating Drosophila reproduction under normal conditions and in stress is discussed.     

Stress response in Drosophila melanogaster strain inactive with decreased tyramine and octopamine contents

Juvenile hormone hydrolysis, tyrosine decarboxylase activity, dopamine content and fitness (viability and fertility) were studied under normal and stress conditions in the adults of Drosophila melanogaster inactive strain carrying a mutation that decreases tyrosine decarboxylase activity and results in the lower contents of tyramine and octopamine. A sexual dimorphism of tyrosine decarboxylase activity, dopamine level and survival under heat stress in inactive flies was found. inactive adults showed higher dopamine levels and lower survival levels under heat stress as compared to wild type (Canton S) adults. Juvenile hormone degradation is decreased in young and increased in mature inactive females as compared to wild type. Fertility of the inactive strain did not differ from that of wild type strain under normal conditions, but after heat exposure the dynamics of its restoration was different. inactive females were found to develop the stress reaction, with juvenile hormone degradation, tyrosine decarboxylase activity, dopamine content and fertility levels used as the reaction indicators.     

Dopamine and octopamine regulate 20-hydroxyecdysone level in vivo in Drosophila

The effects of increased level of dopamine (DA) (feeding flies with DA precursor, L-dihydroxyphenylalanine, L-DOPA) on the level of 20-hydroxyecdysone (20E) and on juvenile hormone (JH) metabolism in young (2-day-old) wild type females (the strain wt) of Drosophila virilis have been studied. Feeding the flies with L-DOPA increased DA content by a factor of 2.5, and led to a considerable increase in 20E level and a decrease of JH degradation (an increase in JH level). We have also measured the levels of 20E in the young (1-day-old) octopamineless females of the strain Tbetah(nM18) and in wild type females, Canton S, of D. melanogaster. The absence of OA led to a considerable decrease in 20E level (earlier it was shown that in the Tbetah(nM18) females, JH degradation was sharply increased). We have studied the effects of JH application on 20E level in 2-day-old wt females of D. virilis and demonstrated that an increase in JH titre results in a steep increase of 20E level. The supposition that biogenic amines act as intermediary between JH and 20E in the control of Drosophila reproduction is discussed.     

Regulation of Reproductive Function in DrosophilaFemales Due to Hormonal Interaction Under Stress Is Genetically Determined

The effect of heat stress (38°C) on the content of octopamine (OA) and 20-hydroxyecdysone (20HE) was studied under normal and stressful conditions in adult flies of Drosophila virilislines contrasting in the level of the juvenile hormone (JH). The wild-type flies (line 101) exhibited a pronounced sex dimorphism for the content of both OA and 20HE, which was substantially lower in this line than in flies of the mutant line 147. The level of both hormones increased in flies of line 101 exposed to heat stress, whereas it remained unchanged in flies of line 147 under the same conditions. The effect of heat stress on the level of JH metabolism and fertility was also studied in D. melanogasterwild-type lines and lines carrying mutations in genes responsible for OA and DA syntheses. In octopamineless females of the Th ^nM18line and in females of the Steline characterized by a doubled content of DA, JH degradation differed from normal: it was increased in both young and mature Th ^nM18females, while decreased in young and increased in mature Steflies. Fertility was substantially lower in the Stethan in the wild-type line. Flies of all of the D. melanogasterlines produced a stress response; however, in mutant lines, both fertility and stress reactivity of the systems controlling JH metabolism differed significantly from that of the wild-type lines. The role of JH, 20HE, OA, and DA interaction in regulation of Drosophilareproduction under stressful conditions is discussed.     

Altered juvenile hormone metabolism, reproduction and stress response in Drosophila adults with genetic ablation of the corpus allatum cells

Juvenile hormone (JH), which controls many developmental and physiological processes in Drosophila melanogaster, is synthesized de novo in the specialized endocrine glands, corpus allatum (CA). The present study concerns JH metabolism, reproduction and stress resistance in Drosophila with genetic ablation of a part of CA cells. The correlated regulation of JH biosynthesis and degradation in Drosophila adults has been found: ablation of CA cells led to (1) a dramatic decrease in activity of the key regulatory enzyme of JH biosynthesis, juvenile hormone acid methyl transferase and (2) a considerable increase in JH-hydrolyzing activity. It has been also shown that ablation of CA cells caused three significant physiological changes: (1) an increase in the intensity of response of JH degradation system to heat stress; (2) a disturbance of reproduction; (3) a decrease in stress resistance. Pharmacological rise of JH level rescued JH-hydrolyzing activity, fecundity and stress resistance in CA-ablated females. Pronouncedly, all the physiological effects caused by CA ablation were significant in females but not in males indicating a sexual dimorphism of JH physiological roles in Drosophila adults.     

Adaptive value of genes controlling the level of biogenic amines in Drosophila

The effects of mutations that change the level of biogenic amines (octopamine and dopamine) on stress-reactivity and fitness of Drosophila imagoes are considered. It has been shown that (1) the biogenic amines represent an important but not triggering factor of the development of stress reaction; (2) under normal conditions, reproduction is regulated by genes that control dopamine metabolic pathways (indirectly via regulation of the juvenile hormone level). Under unfavorable conditions, reproduction is regulated by genes that control octopamine metabolism; (3) heat-stress adaptation depends on expression of genes controlling the background level of dopamine.     

Mechanisms of age-specific regulation of dopamine metabolism by juvenile hormone and 20-hydroxyecdysone in <Emphasis Type="Italic">Drosophila</Emphasis> females

20-hydroxyecdysone (20E) and the juvenile hormone (JH) have an age-specific effect on total dopamine (DA) content in Drosophila (Gruntenko and Rauschenbach 2008). Earlier we studied the mechanism of influence of 20E and JH on DA metabolism in young females (Rauschenbach et al. in J Insect Physiol 53:587–591, 2007a: Arch Insect Biochem Physiol 65:95–102, 2008a; Gruntenko et al. in Arch Insect Biochem Physiol 72:263–269, 2009). Here we investigate the effects of 20E and JH on the activities of the alkaline phosphatase (ALP), tyrosine hydroxylase (TH) and DA-dependent arylalkylamine N-acetyltransferase (AANAT) in mature females of wild type D. virilis under normal conditions and under heat stress (38°C). 20E feeding of the flies led to a substantial decrease in ALP and TH activities and to an increase in AANAT activity in mature females. JH application resulted in an increasing of ALP and TH activities, but did not influence AANAT activity in mature females. A rise in JH and 20E levels was found to change ALP and TH stress reactivities. Mechanisms of age-specific regulation of DA level by 20E and JH in Drosophila females are discussed.     

Downregulation of the dopamine D2-like receptor in corpus allatum affects juvenile hormone synthesis in Drosophila melanogaster females

In Drosophila, juvenile hormone (JH) is synthesized de novo in the specialized endocrine gland, corpusallatum (CA). Dopamine (DA) controls JH levels by either stimulating or inhibiting its synthesis and degradation depending on the developmental stage. The present study focuses on the role of D2-like receptors in the regulation of JH synthesis by dopamine. We show that D2-like receptors (DD2R) are expressed in CA cells of Drosophila melanogaster females. In addition, the level of JH production was analyzed in D. melanogaster females with decreased DD2R expression in CA (vs. corresponding control flies) by assessing multiple indices of JH synthesis (JH-hydrolyzing activity and stress reactivity of the system of JH metabolism, activity and stress reactivity of the alkaline phosphatase, activity and stress reactivity of the tyrosine decarboxylase). The differential value obtained for each index suggests increased JH production in female flies that downregulate DD2R. Based on these findings, we postulate that the DA inhibiting effect on the JH synthesis in D. melanogaster is mediated at least in part via D2-like receptors.     

Stress-reactivity of a Drosophila melanogaster strain with impaired juvenile hormone action

Met(27) is a null allele of the Methoprene-tolerant gene of D. melanogaster that shows resistance to the toxic effects of both juvenile hormone (JH) and a JH analog, methoprene. The mechanism of resistance appears to be altered JH reception. We measured fertility, JH-hydrolyzing activity, and dopamine (DA) levels in Met(27) and Met(+) flies under normal (25 degrees C) and heat-stress (38 degrees C) conditions. We show that under normal conditions Met(27) females have JH-hydrolyzing activity and fertility lower than Met(+), but DA content did not differ between the two strains. At 38 degrees C Met(27) flies show no impairment in JH-hydrolyzing activity in response to stress, but they do show lower DA levels and impaired reproduction. The results with Met(27) are consistent with the previous hypothesis that the alteration in fertility that follows heat stress in D. melanogaster could result from alteration in the JH endocrine system.     

Effects of octopamine on reproduction, juvenile hormone metabolism, dopamine, and 20-hydroxyecdysone contents in Drosophila

The effect of an experimentally increased octopamine content (feeding flies with OA) on the levels of juvenile hormone (JH) degradation, dopamine (DA), and 20-hydroxyecdysone (20E) contents, oogenesis, and fecundity of wild type Drosophila flies has been studied. OA feeding of the flies was found to (1) cause a considerable decrease in JH degradation in females, but not males, of D. melanogaster and D. virilis; (2) have no effect on DA content in D. melanogaster and D. virilis; (3) increase 20E contents in D. virilis females; (4) decrease to a large extent the number of vitellogenic (stages 8-10) and mature (stage 14) oocytes in D. virilis; and (5) decrease the fecundity of D. melanogaster and D. virilis. A possible mechanism of action of OA as a neurohormone on the reproductive function of Drosophila is discussed.     

Effects of 20‐hydroxyecdysone and juvenile hormone on octopamine metabolism in females of Drosophila

The effect of exogenous 20‐hydroxyecdysone (20E) and juvenile hormone (JH) on the activities of the tyrosine decarboxylase (TDC), the first enzyme in octopamine (OA) synthesis, has been studied in young females of wild type D. virilis and D. melanogaster under normal and heat stress (38°C) conditions. Flies fed 20E expressed increased TDC activity in both species. JH application decreased TDC activity in both species. A rise in JH and 20E levels did not prevent a TDC response to heat stress, but changed the response intensity. A long‐term increase in JH titre had no effect on the activity of main OA catabolyzing enzyme, arylalkylamine N‐acetyltransferase, in females of both species. A possible mechanism of regulation of OA levels by 20E and JH in Drosophila females is discussed. © 2009 Wiley Periodicals, Inc.