BROADENING THE SCOPE OF GASTROPOD IMMUNITY: INSIGHTS FROM A NEW SNAIL HOST/PARASITE MODEL
Jonathan Schultz, University of New Mexico
Jonathan H. Schultz, Coen M. Adema
Center for Evolutionary and Theoretical Immunology, Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA
Current insights of gastropod internal defense systems are largely based on a few model organisms that are important for disease transmission or represent economic food sources. Such a narrow scope may not be representative of immune function for a diverse class like the Gastropoda (~60,000 species). The transcriptome and genome of Physella acuta, an understudied gastropod in terms of immunity, was captured using next-generation sequencing (454, Illumina). This also yielded FREP sequences: immune factors known to be somatically mutated and involved in the anti-trematode defense response of Biomphalaria glabrata, a planorbid snail within a sister family of P. acuta. We recorded ~5 FREP sequences, a dramatic reduction in gene sequence number compared to B. glabrata (> 20 sequences). Furthermore, sub-cloning and sequencing of a partial amplicon of FREP1 in P. acuta did not yield variant sequences suggesting that this FREP is not somatically mutated. To determine the role of FREPs in antitrematode defense we exposed P. acuta snails to the parasite Echinostoma paraensei and analyzed protein composition (SDS-PAGE) of P. acuta plasma at 0,2,4, and 8 days post exposure (DPE). FREPs are not prominently part of anti-parasite responses. Additionally, we obtained Illumina RNA-Seq data to analyze FREP gene expression at 0,2, and 8 DPE. In conclusion, study of a novel snail host/parasite model supports the notion that P. acuta FREP genes are reduced in number and lack somatic diversification. Also, immune function differs between the Planorbid and Physid snail families.