Neurohormones as putative circadian clock output signals in the central nervous system of two cricket species

Abstract

Antisera to the neuropeptides corazonin (Crz) and crustacean cardioactive peptide (CCAP) and to the diapause hormone (DH) react with small sets of neurones in the cephalic ganglia of the crickets Dianemobius nigrofasciatus and Allonemobius allardi. The distribution of their immunoreactivities is similar in the two species and overlaps with the locations of presumed circadian clock components in the optic lobes, protocerebrum, tritocerebrum, suboesophageal ganglion (SOG) and frontal ganglion. D. nigrofasciatus contains two Crz-immunoreactive (Crz-ir) cells in each optic lobe, six cell groups in the protocerebrum, four in the tritocerebrum, and one in SOG, whereas A. allardi harbours only five Crz-ir groups in the protocerebrum and four in the tritocerebrum. CCAP immunoreactivity occurs in both species in four protocerebrum cell clusters, four tritocerebrum cell clusters, four SOG cell clusters, one frontal ganglion cell cluster, and two optic lobe cell clusters; D. nigrofasciatus possesses two additional cells with unique links to the lamina in the optic lobe. DH-related antigens are present in four cell clusters in the optic lobe, six (D. nigrofasciatus) or eight (A. allardi) in the protocerebrum, four in the tritocerebrum, and three (A. allardi) or five (D. nigrofasciatus) in the SOG. Some of the detected cells also react with antibody to the clock protein Period (PER) or lie close to PER-ir cells. Crickets reared at two different photoperiods do not differ in the distribution and intensity of immunoreactivities. No changes have been detected during the course of diurnal light/dark cycles, possibly because the antisera react with persistent prohormones, whereas circadian fluctuations may occur at the level of their processing or of hormone release. The projection of immunoreactive fibres to several brain regions, the stomatogastric nervous system and the neurohaemal organs indicates multiple functions of the respective hormones.

Co-localization and unique distributions of two clock proteins CYCLE and CLOCK in the cephalic ganglia of the ground cricket, Allonemobius allardi

“…Our previous results have demonstrated that PER-ir and casein kinase I α (CKIα)-ir are co-localized only in the proximal frontoventral (Pfv) of the OL in Dianemobius nigrofasciatus (Orthoptera: Gryllidae), but that in Allonemobius allardi, co-localization is observed only in the maxillary and mandibular neuromere in the midline of the SOG (Shao et al 2006). This suggests that the locus of circadian neurons may reside in different regions in the two closely related crickets, although our recent data have shown that immunoreactivity against some neuropeptides, such as crustacean cardioactive peptide (CCAP), corazonin, and diapause hormone (DH) are located in the maxillary and mandibular neuromere of the SOG in both species (Sehadová et al 2007). Following an investigation into core oscillator elements (Shao et al 2006) and output elements (Sehadová et al 2007), we have examined the detailed localization and temporal expression patterns of the transcription modulators in A. allardi sampled at 4-h intervals throughout a 24-h period and under different photoperiodic conditions.…”

“…We have previously investigated the distribution of three clock proteins, i.e., PER, CKIε, and cryptochrome (CRY; Shao et al 2006) and three neuropeptides, i.e., CCAP, corazonin, and DH (Sehadová et al 2007) in the cephalic ganglia of the adult ground cricket, A. allardi by immunohistochemistry. We have found that most of the circadianrelated proteins or peptides that we have investigated are prominently expressed in the mandibular and maxillary clusters of neurons in the midline of the SOG and also in the clustered cell bodies of the tritocerebrum.…”

“…The underlined portion was used as antigen to raise antibody against BmCYC the same way as for the rabbit CYC antibody. The rabbit CLK antibody showed unique reactivity in most regions, when compared with the CYC antibody, but showed colocalization in the midline group neurons of the SOG, and hence, possibly with CCAP-ir, and DH-ir (Sehadová et al 2007). …”

“…This suggests that the locus of circadian neurons may reside in different regions in the two closely related crickets, although our recent data have shown that immunoreactivity against some neuropeptides, such as crustacean cardioactive peptide (CCAP), corazonin, and diapause hormone (DH) are located in the maxillary and mandibular neuromere of the SOG in both species (Sehadová et al 2007). Following an investigation into core oscillator elements (Shao et al 2006) and output elements (Sehadová et al 2007), we have examined the detailed localization and temporal expression patterns of the transcription modulators in A. allardi sampled at 4-h intervals throughout a 24-h period and under different photoperiodic conditions. Double-labeling has also been applied to investigate the co-localization of these antigens.…”

Mapping the cellular network of the circadian clock in two cockroach species

“…According to the model of self-generating cycles, PER should enter a nucleus to turn off per gene and form a feedback loop with TIM (van Gelder et al, 2003). However, PER-ir cells of the German cockroach do not show the translocation of PER in the nucleus as commonly found in several insect species (Sauman and Reppert, 1996;Sauman and Hashimi, 1999;Wise et al, 2002;Zavodaska et al, 2003a,b;Sehadova et al, 2006;Shao et al, 2006). These findings are different from Drosophila (Liu et al, 1988;Siwicki et al, 1988).…”