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

Jia You,Yu Wang,Yanfeng Hu,Shuo Wang,Fengjuan Pan

doi:10.3389/fpls.2021.673354

Abstract

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 Heterodera glycines, the most economically damaging parasite of soybean [Glycine max L. (Merr)], has been reported in previous research. However, the family of genes encoding FLPs of H. glycines were not identified and functionally characterized. In this study, an FLP encoding gene Hg-flp-22 was cloned from H. glycines, and its functional characterization was uncovered by using in vitro RNA interference and application of synthetic peptides. Bioinformatics analysis showed that flp-22 is widely expressed in multiple nematode species, where they encode the highly conserved KWMRFamide motifs. Quantitative real-time (qRT)-PCR results revealed that Hg-flp-22 was highly expressed in the infective second-stage juveniles (J2s) and adult males. Silencing of Hg-flp-22 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 H. glycines but not in Meloidogyne incognita. In addition, the number of H. glycines females on the host roots was found to be significantly higher in Hg-FLP-22b treated nematodes than the ddH2O-treated control J2s. These results presented in this study elucidated that Hg-flp-22 plays a role in regulating locomotion and infection of H. glycines. This suggests the potential of FLP signaling as putative control targets for H. glycines in soybean production.

Highlights

Soybean [Glycine max L. (Merr)] is an important and frequently consumed crop and serves as a major source of protein and oil worldwide
Basic Local Alignment Search Tool (BLAST) analysis was conducted in the available nematode expressed sequence tag (EST), genomic, and transcriptomic databases using Hg-flp-22 as a search query, and Hg-flp-22 complements were identified in 42 nematode species, including free-living and animal- and plant-parasitic (Supplementary Table 2)
It is worth noting that Hg-FMRFamide-like peptides (FLPs)-22 was more similar to a homolog from Globodera rostochiensis (Gr-FLP-22, BM343164.1), sharing 72% sequence identity; the identity of two peptides, QPAGGVKWMRFa and TPQGKWMRFa, in H. glycines and G. rostochiensis were 100% (Figure 1B)

Summary

Introduction

Soybean [Glycine max L. (Merr)] is an important and frequently consumed crop and serves as a major source of protein and oil worldwide. Its yield is strongly affected by various pests and pathogens, including plant-parasitic nematodes (PPN). The soybean cyst nematode, Heterodera glycines Ichinohe, a sedentary and endoparasitic nematode, is one of FLP-22 Influences Heterodera glycines Parasitism the most damaging pests attacking soybean (Niblack et al, 2006). An estimated annual soybean yield loss by H. glycines has been reported to be around US$1 billion in the United States (Koenning and Wrather, 2010). This nematode is a major constraint to soybean production in China (Ou et al, 2008; Zheng et al, 2009; Wang et al, 2015; Peng et al, 2016). Alternative new approaches are needed for controlling this widespread and destructive pest

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