Soybean cyst nematode (SCN, Heterodera glycines Ichinohe), is a devastating pathogen in soybean. The infective juveniles of nematodes can use phytochemical signals (semiochemicals), released into the rhizosphere as important cues for host seeking, host location and penetration. Disrupting host-seeking signals to prevent nematode infection can reduce the effort required to control nematodes in the soil compared to controlling parasitic stages inside the plant.
The attraction and repellence of nematodes to chemical signals are closely tied to their chemosensory system, such as G protein-coupled receptors (GPCRs). Elucidating the diversity of receptors or receptor signal transduction in plant parasitic nematodes and understanding nematode response mechanisms to chemical signals could provide new possibilities for nematicide target design and consequently improve pest control.
A research team led by Prof. WANG Congli from the Northeast Institute of Geography and Agroecology of the Chinese Academy of Sciences, utilize full-length transcriptome sequencing for the first time to investigate the SCN behavior response to attractive acidic pH, basic pH and salt solutions including extreme pH environments (pH 4.5, 5.25, 8.6, 10 and NaCl). This study was published in Journal of Agricultural & Food Chemistry.
The researchers chose soybean cyst nematodes as a model system to investigate plant-parasitic nematode behavior and gene expression changes in response to acidic and basic pH and salt signals.
Wormlab software was utilized for the first time to analyze plant-parasitic nematode behavior and the results demonstrated different responses to pH and salt signals. Transcriptome sequencing indicated that an average of 4.36 Gbp of clean reads per nematode sample were generated and 3,972 novel genes and 29,529 novel transcripts were identified. Sequence structural variation during or post transcription may be associated with the nematode’s behavioral response.
The functional analysis of 1817/4962 differentially expressed genes (DEGs) showed that signal transduction pathways, including transmembrane receptors, ion channels and Ca2+ transporters, were activated, but pathways involved in nematode development (e.g., ribosome) and energy production (e.g., oxidative phosphorylation) were inhibited.
The activated transmembrane GPCR receptors included chemoreceptor Srsx, Wnt receptor MOM-5, dopamine receptor F59.D12.1, peptide receptor NPR-18, mAChR, and hormone thyrotropin receptor TRHR.
Additionally, nAChR, GABAB receptor, and guanylate cyclase receptor GCY-18 could regulate ion channels, while ion transporters PMCA and ion channels VGCC and TRP-1 (TRPC4) were also activated.
The receptor activation and inhibition in growth and development indicated that nematodes sustained energy balance by regulating metabolic pathway in favorable conditions, which also explained why soybean cyst nematode disease is severe in acidic, basic or high salt soil. A regulatory model responding to pH and salt ion stimulation was established by the combination of DEGs and protein─protein interaction analysis.
The findings suggest that these identified receptors and ion channels might be potential targets for nematicides to control plant parasitic nematodes or drug discovery to control human or animal parasitic nematodes. In addition, this study suggests that H. glycines could be utilized as a model for developing drugs to combat acidic or basic pH or high salt environments.
Contact:
WANG Congli
Northeast Institute of Geography and Agroecology
E-mail: wangcongli@iga.ac.cn
