Distribution patterns of SIFamide in hemimetabolous insects

Veranstaltungsname: 10th Göttingen Meeting of the German Neuroscience Society 2013

The neuropeptide SIFamide shows a particularly high degree of conservation regarding its sequence within the phylum Arthropoda. Several isoforms of the peptide have been described in various insects, crustaceans, and a tick showing only little variations at the N-terminus, often only at the first amino acid. The distribution pattern in brains of holometabolous insects showed also striking similarities. In the blowfly Neobellieria bullata, the honeybee Apis mellifera, and many other insects only four relatively large somata in the pars intercerebralis (PI) expressed immunoreactivity against SIFamide. Generally, varicose branchings are widely spread in brains of the adults. Recent studies investigating neuropeptide distribution in Drosophila melanogaster located three pairs of additional SIF-immunoreactive (-ir) cell bodies in the dorsolateral protocerebrum. Moreover, in the tobacco hornworm Manduca sexta another SIF-ir soma was detected anterior to the calyx, while weakly stained cells were observed dorsally and ventrally. Unfortunately, the peptide is not as well studied in hemimetabolous insects as in the holometabolous group. With antibodies against SIFamide (antiAYRKPPFNGSIFamide; antibody provided by Dr. Jan Veenstra) we investigated the occurrence of the peptide in the Madeira cockroach Rhyparobia (Leucophaea) maderae, the American cockroach Periplaneta americana, and the Indian domino cockroach Therea petiveriana. In each species, also four big cells in the PI expressed strong immunoreactivity. Furthermore, smaller cells in the PI as well as other groups of soma in the lateral protocerebrum and in close vicinity to the calyx could be observed. Moreover, we identified the Rhm-SIFamide (TYRKPPFNGSIFamide) with matrix-assisted laser desorption/ionization time of flight mass spectrometry in preparations of single glomeruli of the antennal lobe as well as in cell clusters of the PI. The Sequence of the Rhm-SIFamide is identical to previously identified SIFamides in P. americana, Bombyx mori, Tenebrio molitor and Tribolium castaneum. To conclude, the highly conserved sequence supports an important physiological function of this peptide. The additional immunoreactive cell groups might represent the originally distribution of SIFamide, which hints to further physiological roles in basal insects that were partially lost during evolution. Future behavioural assays in combination with peptide injections will investigate the role of SIFamide in R. maderae, an established model organism in circadian research. [Supported by DFG grant STE531/21-1 to MS]

Zuletzt aktualisiert 2018-05-12 um 16:41