De Novo Transcriptomic Response of Pirenella cingulata (Gastropoda) Infected with Acanthotrema tridactyla (Trematoda)

Pirenella cingulata- a snail from an intertidal mudflat serves as the first intermediate host of digenean trematode parasites. These trematode parasites castrate their host and alter the host's physiology for their own success and proliferation. In this study, we investigate the interaction between Pirenella cingulata and the trematode Acanthotrema tridactyla using a de novo transcriptomic approach.

RNA was extracted from both infected and non-infected Pirenella cingulata. High-throughput RNA sequencing was performed, and only healthy individuals were used for de novo assembly of the transcriptome. Furthermore, the transcripts were annotated, followed by the identification of differentially expressed genes using the DESeq2 package.

We have identified 91 differentially expressed host genes that mostly suppress immune responses, altering metabolic and cytoskeletal-related functions. Downregulation of immune-related genes, including Cathepsin L, beta 1,3-glucan binding protein, scavenger receptors, and histone 3 (H3) suggest immune suppression. Gluconeogenesis, a key metabolic pathway, was compromised by downregulating the activity of alkaline phosphatase and lipase. Gastropods mediate immune-related 'oxidative burst' by generation of ROS- a mechanism to cope with parasites, which trematodes countered by downregulating xanthine hydrogenase/oxidase. Cytoskeletal proteins like actins was downregulated, used for encapsulation and phagocytosis, implying a compromised immune system.

This study provides insights into host-parasite interaction with the understanding of the immune functional response, metabolic and cytoskeletal-related processes of parasitised gastropods.