Disruption of insulin signalling affects the neuroendocrine stress reaction in Drosophila females.

Juvenile hormone (JH) and dopamine are involved in the stress response in insects. The insulin/insulin-like growth factor signalling pathway has also recently been found to be involved in the regulation of various processes, including stress tolerance. However, the relationships between the JH, dopamine and insulin signalling pathways remain unclear.

[The DD2R gene expression level in the corpus allatum affects the fitness of female Drosophila melanogaster].

The effect of tissue-specific suppression of the dopamine D2-like receptor gene (DD2R) in the corpus allatum (CA), the gland that synthesizes juvenile hormone (JH) on the Drosophila melanogaster resistance to heat stress has been studied. A decreased expression of the DD2R gene in the CA has been found to substantially decrease the heat stress resistance of adult transgenic female, but not male, D. melanogaster compared to the control group, this phenomenon being weakly pronounced in juvenile flies.

[Inhibition of DD2R gene expression in the corpus allatum activates alkaline phosphatase in female Drosophila melanogaster].

Tissue-specific inhibition of the expression of the D2-like dopamine receptor gene (DD2R) in the corpus allatum (CA), which is a gland that synthesizes the juvenile hormone (JH), was tested for effect on alkaline phosphatase (AP) activity and the intensity of the AP response to heat stress (stress reactivity) in female Drosophila melanogaster. AP activity and AP stress reactivity in transgenic females with lower DD2R expression in the CA were higher than in control flies. A pharmacological elevation in JH increased AP activity in females of the control strains.

Mechanisms of age-specific regulation of dopamine metabolism by juvenile hormone and 20-hydroxyecdysone in Drosophila 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.

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.

Dopamine down-regulates activity of alkaline phosphatase in Drosophila: the role of D2-like receptors.

The effect of a rise in dopamine (DA) level as a result of a mutation, stress or pharmacological treatment on the activity of the enzyme of its synthesis, alkaline phosphatase (ALP) in females of Drosophila virilis and Drosophila melanogaster has been studied. It has been found that regardless of its nature, a rise in DA level has a negative effect on ALP activity, which indicates that DA down-regulates activity of the enzyme. The effects of bromocriptine (an agonist of Drosophila dopamine 2-like receptor (DD2R)) on ALP activity have been studied.

[Biogenic amines regulate the reproductive function in Drosophila as neurohormones].

We studied the influence of experimental increase in the octopamine and dopamine content on the level of juvenile hormone degradation, oogenesis, and fertility in wild type D. virilis flies. Feeding of flies on octopamine led to a significantly decreased level of juvenile hormone degradation (increased titer) in young and sexually mature females, rather than in males, markedly decreased the number of vitellogenic (stages 8-10) and mature (stage 14) oocytes), and sharply reduced fertility.

[The mechanism of the effect of apterous56f mutation on the reproductive function of Drosophila melanogaster].

The effects of L-dihydroxyphenylalanine (L-DOPA) and 20-hydroxyecdysone (20E) were studied with respect to the content of dopamine (DA), intensity of the juvenile hormone (JH) degradation, and fecundity of the wildtype flies (Canton S) and JH-deficient apterous56f mutants (in young females, carrying this mutation, the levels of DA and 20E production were strongly increased). Fly feeding with L-DOPA proved to increase the level of DA in a dose-dependent manner and reduce JH degradation in 2-day-old females of both strains. Feeding with 20E produced the same effect.

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.

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.

The effect of mutations altering biogenic amine metabolism in Drosophila on viability and the response to environmental stresses.

Dopamine (DA) content, tyrosine decarboxylase (TDC) activity and survival were studied under normal and environmental stress conditions in the ste and e strains carrying ebony mutation increasing DA level and the octopamineless strain Tbetah(nM18) of Drosophila melanogaster. Wild-type strains Canton S and Oregon R, and strain p845 from which Tbetah(nM18) strain was derived were used as controls. Sexual dimorphism of TDC activity, DA content, and survival in flies of all D.