Expression of a neuropeptide similar to allatotropin in free living turbellaria (platyhelminthes)
Introduction
Cell–cell integration is a basic feature to coordinate functions in all living organisms. Then, mechanisms coordinating functions locally as well as systemically are likely to have appeared early in evolution. This is achieved by mean of different ways (e.g. paracrine, endocrine, synaptic) but always involves chemical messengers including molecules with different chemical natures as mineral ions, lipids, aminoacids and peptides. Even in protists (Le Roith et al., 1980), sponges (Lentz, 1966, Weyrer et al., 1999) and cnidarians (Grimmelikhuijzen et al., 1991, Grimmelikhuijzen et al., 1996, Grimmelikhuijzen et al., 2002, Hansen et al., 2002), the existence of cellular mediators was documented, and several native neuropeptides were isolated and characterized.
In Turbellaria, neuropeptides seem to be particularly important as myoregulators, controlling the activity of muscles at the level of both digestive and reproductive organs (Gustafsson et al., 2002). In fact, several neuropeptides have been detected and characterized in Plathyelminthes and Acoela (Gustafsson et al., 2002, Johnston et al., 1995, Johnston et al., 1996, Kreshchenko, 2008, Kreshchenko et al., 2008, McVeigh et al., 2009, Mousley et al., 2004, Reuter et al., 1998, Reuter et al., 2001, Wikgren and Reuter, 1985).
Allatotropin (AT), a neuropeptide originally isolated from the brain of the Lepidoptera Manduca sexta based on its ability to stimulate the synthesis of juvenile hormones (JHs) (Kataoka et al., 1989), has also been isolated and characterized in several other insect species (Abdel-latief et al., 2003, Paemen et al., 1991, Park et al., 2002, Scheng et al., 2007, Truesdell et al., 2000, Veenstra and Costes, 1999) and even in some other invertebrate groups (Elekonich and Horodyski, 2003, Veenstra, 2010), both in nervous as well as in epithelial tissues (Riccillo and Ronderos, 2010, Santini and Ronderos, 2009a, Santini and Ronderos, 2009b, Sterkel et al., 2010). Despite the function as a JHs regulator, as other many peptides, AT has proved to be pleiotropic acting as a cardioaccelerator (Koladich et al., 2002, Rudwall et al., 2000, Sterkel et al., 2010, Veenstra et al., 1994), inhibiting ion transport throughout epithelia (Lee et al., 1998), and also acting as a myoestimulator at the level of the digestive system in several insect species (Duve et al., 1999, Duve et al., 2000, Matthews et al., 2007, Santini and Ronderos, 2007, Sterkel et al., 2010). Indeed, a new activity controlling the release of digestive enzymes was recently described in insects (Lwalaba et al., 2009).
On the basis of the multiplicity of functions described for this peptide, including a so specific one for insects (JHs synthesis regulation), and the probability of that this function could not be primitive, we decide to analyze the expression of AT in two groups of Turbellaria (Catenulida, Macrostomida), and its probable functional relationship with muscle tissues.
Section snippets
Animals
Specimens of free-living turbellarian Macrostomum sp. (Macrostomida) were collected at a rainwater pond in Pereyra Iraola Park (34°51′S; 58°03′W), while specimens of Stenostomum sp. (Catenulida) were collected at another rainwater pond at Berisso (34°57′S; 57°48′W), both localities situated near to the city of La Plata (Buenos Aires Province, Argentina). The specimens were obtained during summer and autumn 2010 and were maintained in the water of origin under a 12:12 h light/dark period until
Results
The analysis reveals the presence of immunoreactive cells in both groups of free living flatworms under study: Catenulida (Stenostomum sp.) and Macrostomida (Macrostomum sp.). The omission of the primary antibody against A. aegypti AT abolished the labeling, and the preadsorption of the primary antibody with the immunizing peptide clearly diminished the staining (data not shown).
Discussion
Our results show the expression of an AT-like peptide in both groups of free living Turbellaria analyzed. The peptide is present in cells resembling neurons, and distributed in different regions of the body of the flatworms. The simultaneous analysis of the expression of the peptide with phalloidin, suggests that the neurons producing this peptide have a functional relationship with muscle fibers, particularly at the level of the pharynx in the two turbellarian groups. Indeed, in Catenulida, in
Acknowledgements
The authors wish to thank Dr. Fernando G. Noriega (Florida International University Florida, USA) for generously supplying us with Allatotropin and Allatotropin-antibody and Mr. J. Alonso for the assistance in the field work. This study was financed with founds from the PICT 01287 (SECyT – Argentina).
References (46)
- et al.
Molecular characterisation of cDNAs from the fall armyworm Spodoptera frugiperda encoding Manduca sexta allatotropin and allatostatin preprohormone peptides
Insect Biochem. Mol. Biol.
(2003) - et al.
Insect allatotropins belong to a family of structurally-related myoactive peptides present in several invertebrate phyla
Peptides
(2003) - et al.
Peptides in the nervous system of cnidarians: structure, functions and biosynthesis
Int. Rev. Cytol.
(1996) - et al.
Neuropeptides in flatworms
Peptides
(2002) - et al.
GYIRFamide: a novel FMRFamide-related peptide (FaRP) from the triclad turbellarian, Dugesia tigrina
Biochem. Biophys. Res. Commun.
(1995) - et al.
Cardioacceleratory effects of Manduca sexta allatotropin in the true armyworm moth Pseudaletia unipuncta
Peptides
(2002) - et al.
Interactions between allatostatins and allatotropin on spontaneous contractions of the foregut of larval Lacanobia oleracea
J. Insect Physiol.
(2007) - et al.
Discovery of multiple neuropeptide families in the phylum Platyhelminthes
Int. J. Parasitol.
(2009) - et al.
Arthropod FMRFamide-related peptides modulate muscle activity in helminths
Int. J. Parasitol.
(2004) - et al.
Lom-AG-Myotropin: a novel myotropic peptide from the male accesory glands of Locusta migratoria
Peptides
(1991)