FMRFamide-like peptides in root knot nematodes and their potential role in nematode physiology

Abstract

AbstractFMRFamide-like peptides (FLPs) are a diverse group of neuropeptides that are expressed abundantly in nematodes. They exert potent physiological effects on locomotory, feeding and reproductive musculature and also act as neuromodulators. However, little is known about the specific expression patterns and functions of individual peptides. The current study employed rapid amplification of cDNA ends-polymerase chain reaction (RACE-PCR) to characterizeflpgenes from infective juveniles of the root knot nematodes,Meloidogyne incognitaandMeloidogyne minor. The peptides identified from these transcripts are sequelogs of FLPs from the free-living nematode,Caenorhabditis elegans; the genes have therefore been designated asMi-flp-1,Mi-flp-7,Mi-flp-12,Mm-flp-12andMi-flp-14.Mi-flp-1encodes five FLPs with the common C-terminal moiety, NFLRFamide.Mi-flp-7encodes two copies of APLDRSALVRFamide and APLDRAAMVRFamide and one copy of APFDRSSMVRFamide.Mi-flp-12andMm-flp-12encode the novel peptide KNNKFEFIRFamide (a longer version of RNKFEFIRFamide found inC. elegans).Mi-flp-14encodes a single copy of KHEYLRFamide (commonly known as AF2 and regarded as the most abundant nematode FLP), and a single copy of the novel peptide KHEFVRFamide. These FLPs share a high degree of conservation betweenMeloidogynespecies and nematodes from other clades, including those of humans and animals, perhaps suggesting a common neurophysiological role which may be exploited by novel drugs. FLP immunoreactivity was observed for the first time inMeloidogyne, in the circumpharyngeal nerve ring, pharyngeal nerves and ventral nerve cord. Additionally,in situhybridization revealedMi-flp-12expression in an RIR-like neuron andMi-flp-14expression in SMB-like neurons‡, respectively. These localizations imply physiological roles for FLP-12 and FLP-14 peptides, including locomotion and sensory perception.