allatostatin-1 and farnesoic-acid

Juvenile hormones (JHs) are key regulators of both metamorphosis and adult reproductive processes. Farnesoic acid O-methyltransferase (FAMeT) is thought to be an important enzyme in the JH biosynthetic pathway, catalyzing methylation of farnesoic acid (FA) to methyl farnesoate (MF). Previous evidence in other insects suggested that FAMeT is rate limiting and regulated by a neuropeptide family, the allatostatins. A full-length cDNA encoding a 296 amino acid putative FAMeT has been isolated. A recombinant (r)FAMeT was cloned, expressed and a specific antiserum generated. rFAMeT was assayed for enzymatic activity using a radiochemical assay. In this assay, no activity was detected either with rFAMeT alone or when added to a corpus allatum CA extract. Immunohistochemical analysis was used to confirm the presence of FAMeT in the CA of Drosophila melanogaster ring gland. Analysis of MF, JHIII and JHB3 release in wild type and mutant stocks in the presence and absence of Drome AST (PISCF-type) suggest that Drosophila FAMeT has little if any effect on sesquiterpenoid biosynthesis. Drome AST appears to have a select effect on JH bisepoxide biosynthesis and not MF or JHIII. Additional analysis of MF, JHIII and JHB3 release in strains with a deficiency or decrease of FAMeT compared to wild type shows no significant decrease in MF, JHIII or JH bisepoxide synthesis. Deficiency strains that reduce the level of FAMeT showed reduced longevity relative to wildtype but this result may be due to other genetic influences.

Topics: Amino Acid Sequence; Animals; Corpora Allata; Drosophila melanogaster; Drosophila Proteins; Fatty Acids, Monounsaturated; Fatty Acids, Unsaturated; Female; Gene Deletion; Juvenile Hormones; Larva; Longevity; Male; Methyltransferases; Molecular Sequence Data; Neuropeptides; Recombinant Proteins; Sequence Alignment; Sequence Homology, Amino Acid

Decapod crustaceans do not appear to produce juvenile hormone, but rather its immediate precursor, methyl farnesoate (MF). Both MF and its immediate precursor, farnesoic acid (FA) are produced by the mandibular organs (MO) in crustaceans. The MO are homologous to the insect corpora allata (CA), the site of juvenile hormone biosynthesis. However, the FGLamide allatostatin (ASTs) peptides, of which there are about 60 distinct forms reported from crustaceans, have previously been found to have no effect on MO activity in crustaceans. We have identified by immunocytochemistry the presence of FGLamide-like AST immunoreactivity in neurosecretory cells throughout the CNS as well as in neurohaemal structures such as the sinus gland and pericardial organs. The ASTs are likely delivered to the MO hormonally and/or by local neurohaemal release. Using MO from adult males, we have found wide variability between animals in the in vitro rates of MF and FA biosynthesis. Treatment with Dippu-ASTs has a statistically significant stimulatory effect on MF synthesis, but only in MO that are initially producing MF at lower rates. No effect on FA production was observed, suggesting that the FGLamide ASTs exert their effect on the o-methyl transferase, the enzyme responsible for the conversion of FA to MF.

Topics: Animals; Astacoidea; Eye; Fatty Acids, Unsaturated; Gene Expression Regulation; Hemolymph; Immunohistochemistry; Male; Neuropeptides; Oligopeptides

We investigated the role of head factors and allatostatins (ASs) on the regulation of juvenile hormone (JH) synthesis in female adult mosquito. The biosynthetic activity of the Aedes aegypti corpora allata (CA) in vitro was inhibited by factors present in the head. Disconnecting the CA from the brain resulted in a significant increase in the rate of JH biosynthesis. Inhibition was not dependent on intact nervous connections; co-incubation of CA with brains or brain extracts resulted in a significant decrease of JH biosynthesis. This inhibitory effect of brain extracts was reversible and heat stable; extracts lost the inhibitory activity after proteinase K digestion suggesting a peptidic structure. In a first attempt to elucidate the nature of this inhibitory factor, we tested in our CA in vitro system the effect of members of two families of allatostatins already described in mosquitoes. Anopheles gambiae PISCF-allatostatin (homolog to Manduca PISCF-allatostatin) significantly inhibited JH synthesis, while Ae. aegypti YXFGL-amide-allatostatins (homologs to cockroach YXFGL-amide-allatostatins) did not affect JH synthesis. These results represent the first description of an allatostatic effect of PISCF-allatostatins outside the Lepidoptera.

Topics: Aedes; Animal Feed; Animals; Blood; Brain; Brain Chemistry; Corpora Allata; Culture Media, Conditioned; Denervation; Endopeptidase K; Fatty Acids, Unsaturated; Female; Gene Expression; Gene Expression Regulation; Hormone Antagonists; Hot Temperature; In Vitro Techniques; Juvenile Hormones; Neuropeptides; Time Factors; Tissue Extracts