Neuropeptides predicted from the transcriptome analysis of the gray garden slug Deroceras reticulatum

Authors: AHN, SEUNG-JOON - Oregon State University; Martin, Ruth; RAO, SUJAYA - Oregon State University; Choi, Man-Yeon

Submitted to: Peptides
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2017
Publication Date: 5/11/2017
Citation: Ahn, S., Martin, R.C., Rao, S., Choi, M.Y. 2017. Neuropeptides predicted from the transcriptome analysis of the gray garden slug Deroceras reticulatum. Peptides. 93:51-63. doi: 10.1016/j.peptides.2017.05.005.

Interpretive Summary: The gray garden slug, Deroceras reticulatum, is the most destructive and omnivorous pest on a variety of crops in greenhouses and fields. Slugs affect a wide range of cropping systems including seed production, field crops, row crops, Christmas tree farms, and horticultural nurseries. In new fields, the cost of bait applications, direct loss of plants, and the cost of replanting is estimated to cost the seed industry > $50 million. In established grass seed fields, slug bait applications are estimated at ~$7 million annually, with an additional $38 million in losses from crop damage in Oregon. Those economic impacts are increasing every year. Currently the most commonly used control method relies on chemical pesticides that are mixed in pellet bait-based products for growers. There are environmental risks associated with this control method including chemical residue, effect on non-target arthropods, and human health risks. In addition, there is the risk that slug populations in the field will develop resistance. Therefore, it is essential to develop appropriate management strategies which focus on biologically-based environmentally friendly alternatives. Studies on the slug mainly focused on its ecology, biology, pest status, and control, but, virtually nothing known about peptide hormones and their biological signaling due to lack of the research of molecular biology for the gray garden slug. Therefore, RNA sequences would be provide essential data to facilitate a better understanding of slug physiology and to develop novel biologically-based control methods for the slug. Scientists from USDA-ARS and Oregon State University, at Corvallis, OR identified and characterized the entire profile of neuropeptide genes by RNA seq technique. Our report provides the comprehensive transcriptome data of the gray garden slug and its rich repertoire of putative peptide sequences. Our results possibly offer a novel control method for this pest insect in the future.

Technical Abstract: The gray garden slug, Deroceras reticulatum (Gastropoda: Pulmonata), is one of the most common terrestrial molluscs. Studies on D. reticulatum have mainly focused on ecology and biology due to severe damages on a wide range of vegetables and field crops. However, little is known about hormonal signaling and genetic sequences for neuropeptides. This study, therefore, aimed to establish the RNA sequencing of the slug species and to identify a comprehensive repertoire of neuropeptides in this slug. Illumina high-throughput sequencing of the whole body transcriptome of the slug generated a total of 5.9 billion raw paired-end reads. De novo assembly by Trinity resulted in 143,575 transcripts and further filtration selected 120,553 unigenes. Gene Ontology terms were assigned to 30,588 unigenes, composed of biological process (37%), cellular component (30%) and molecular function (33%). Functional annotation revealed 39,987 unigenes with hits, which were further categorized into important functional groups based on sequence abundance. Neuropeptides, ion channels, ribosomal proteins, G protein-coupled receptors, detoxification, immunity and cytoskeleton-related sequences were dominated dominant among the transcripts. Neuropeptides function as neurohormones, neurotransmitters and neuromodulators for a variety of physiological activities in molluscs. We identified 57 putative neuropeptide precursor genes including achatin, allatostatin A, B and C, allatotropin, APGWamide, CCAP, cerebrin, conopressin, elevenin, ELH, FCAP, FFamide, FVamide, GGNG, GnRH, NdWFamide, NKY, PKYMDT, myomodulin, pleurin, sCAP, CCK/SK, FMRFamide, FxRIamide, LFRFamid, luquin, NPF, and tachykinin. Over 320 peptides were predicted from these precursors in this study. Our results provide the comprehensive transcriptome data of the gray garden slug and its rich repertoire of putative neuropeptide sequences, laying a foundation of for developing molecular approaches to control terrestrial pest slugs.