Abstract
In the mutualistic relationship between the squid Euprymna tasmanica and the bioluminescent bacterium Vibrio fischeri, several host factors, including immune-related proteins, are known to interact and respond specifically and exclusively to the presence of the symbiont. In squid and octopus, the white body is considered to be an immune organ mainly due to the fact that blood cells, or hemocytes, are known to be present in high numbers and in different developmental stages. Hence, the white body has been described as the site of hematopoiesis in cephalopods. However, to our knowledge, there are no studies showing any molecular evidence of such functions. In this study, we performed a transcriptomic analysis of white body tissue of the Southern dumpling squid, E. tasmanica. Our primary goal was to gain insights into the functions of this tissue and to test for the presence of gene transcripts associated with hematopoietic and immune processes. Several hematopoiesis genes including CPSF1, GATA 2, TFIID, and FGFR2 were found to be expressed in the white body. In addition, transcripts associated with immune-related signal transduction pathways, such as the toll-like receptor/NF-κβ, and MAPK pathways were also found, as well as other immune genes previously identified in E. tasmanica’s sister species, E. scolopes. This study is the first to analyze an immune organ within cephalopods, and to provide gene expression data supporting the white body as a hematopoietic tissue.
Highlights
It is widely known that all, if not most, organisms establish mutualistic relationships with bacteria
Based on protocols previously used with Euprymna scolopes, experimental animals were euthanized in artificial seawater (ASW) containing 2% ethanol before dissection, [16,17,18]
The fact that only 20.37% of the transcripts found annotated BLAST hits suggests that there may be a substantial number of novel genes in E. tasmanica that remain to be characterized, and emphasizes the need to study cephalopods in more detail to obtain a better understanding of their gene composition and physiology
Summary
It is widely known that all, if not most, organisms establish mutualistic relationships with bacteria. These associations benefit hosts in a variety of ways, which include but are not limited to: metabolic function, disease prevention, antimicrobial peptide production, and nitrogen fixation [1,2,3,4]. The association between squid of the genus Euprymna and the Gram negative bacterium Vibrio fischeri is one of the most studied animal- mutualistic bacterial models. PLOS ONE | DOI:10.1371/journal.pone.0119949 March 16, 2015
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