Extraordinary diversity among members of the large gene family, 185/333, from the purple sea urchin, Strongylocentrotus purpuratus

摘要

Background Recent analysis of immune-related genes within the sea urchin genome revealed a number of large gene families with vertebrate homologues, such as the Toll-like and NOD/NALP-like receptor families and C-type lectins in addition to a rudimentary complement system. Therefore, the immune response of the purple sea urchin appears to be more complex than previously believed. Another component of the sea urchin immune response is an unusual family of mRNAs, known as 185/333, which is strongly upregulated in response to pathogen challenge. The work presented here indicates that this family of transcripts is derived from an unexpectedly diverse gene family. Results The 185/333 genes are small (185/333 sequences. The genes were closely linked and flanked by short repeats. The repeats within and between the genes may promote their diversification through gene conversion, recombination, and meiotic mispairing. Conclusion The diversity of the 185/333 gene family represents an intriguing addition to what is known about the S. purpuratus immune response, and provides further evidence that invertebrate immune systems are neither simple nor static.