FMRFamide-Like Peptide 22 Influences the Head Movement, Host Finding, and Infection of .

The FMRFamide-like peptides (FLPs) represent the largest family of nematode neuropeptides and are involved in multiple parasitic activities. The immunoreactivity to FMRFamide within the nervous system of , the most economically damaging parasite of soybean [ L. (Merr)], has been reported in previous research. However, the family of genes encoding FLPs of were not identified and functionally characterized. In this study, an FLP encoding gene was cloned from , and its functional characterization was uncovered by using RNA interference and application of synthetic peptides. Bioinformatics analysis showed that is widely expressed in multiple nematode species, where they encode the highly conserved KWMRFamide motifs. Quantitative real-time (qRT)-PCR results revealed that was highly expressed in the infective second-stage juveniles (J2s) and adult males. Silencing of resulted in the reduced movement of J2s to the host root and reduced penetration ability, as well as a reduction in their subsequent number of females. Behavior and infection assays demonstrated that application of synthetic peptides Hg-FLP-22b (TPQGKWMRFa) and Hg-FLP-22c (KMAIEGGKWVRFa) significantly increased the head movement frequency and host invasion abilities in but not in . In addition, the number of females on the host roots was found to be significantly higher in Hg-FLP-22b treated nematodes than the ddHO-treated control J2s. These results presented in this study elucidated that plays a role in regulating locomotion and infection of . This suggests the potential of FLP signaling as putative control targets for in soybean production.