Immune-Related Gene Profiles and Differential Expression in the Grey Garden Slug Deroceras reticulatum Infected with the Parasitic Nematode Phasmarhabditis hermaphrodita.

Simple Summary: Slugs and snails are widely distributed in natural humid habitats, and they are a worldwide problem in agriculture. The grey garden slug, a common terrestrial species, is considered the most severe pest of vegetables and field crops. Currently, the most common slug control methods rely on chemical pesticides, which can be damaging to the environment and human health. Nematodes are important natural enemies of slugs, and one species has been used as a commercial product for three decades. This study investigated and analyzed the differential gene expression profiles between nematode-infected slugs and uninfected slugs and identified the genes associated with immunity in the grey garden slug. The results provide a starting point for understanding the molecular mechanism of immune genes and physiological pathways, facilitating the identification of biological targets for slug management strategies in the field. The grey garden slug (Deroceras reticulatum), a common terrestrial slug native to Europe with a global distribution including North America, is commonly considered the most severe slug pest in agriculture. The nematode Phasmarhabditis hermaphrodita, which has been used in the U.K. and Europe as a commercial biocontrol agent since 1994, has also recently been collected in Oregon and California and has long been considered a candidate biocontrol agent for slug management in the U.S. In this study, we report differential gene expressions in nematode-infected slugs using RNA-seq to identify slug immune-related genes against nematodes. Comparison of gene expression levels between the whole bodies of a nematode-infected slug (N-S) and an uninfected control slug (C-S) revealed that there were a total of 39,380 regulated unigenes, of which 3084 (3%) were upregulated and 6761 (6%) were downregulated at greater than 2-fold change (FC > 2) in the nematode-infected slug. To further investigate the biological functions of differentially expressed genes (DEGs), gene ontology (GO) and functional enrichment analysis were performed to map the DEGs to terms in the GO, eukaryotic ortholog groups of proteins (KOG) and Kyoto Encyclopedia of Genes and Genome Pathway (KEGG) databases. Among these DEGs, approximately 228 genes associated with immunity or immune-related pathways were upregulated 2-fold or more in the N-S compared to C-S. These genes include toll, Imd, JNK, scavenger receptors (SCRs), C-type lectins (CTLs), immunoglobulin-like domains, and JAK/STAT63 signaling pathways. From the RNA-seq results, we selected 18 genes and confirmed their expression levels by qRT-PCR. Our findings provide insights into the immune response of slugs during nematode infection. These studies provide fundamental information that will be valuable for the development of new methods of pest slug control using pathogenic nematodes in the field. [ABSTRACT FROM AUTHOR]