CADAVID, Luis F.; POWELL, Anahid; NICOTRA, Matthew; MORENO, Maria; BUSS, Leo; University of New Mexico; University of California, Irvine; Yale University; Yale University; Yale University: Genetics of Allorecognition in the Hydroyd Hydractinia

Most sessile colonial invertebrates have the ability to distinguish between their own tissues and those of unrelated members of the same species. Isogenic (self) colonies fuse whereas allogenic (non-self) colonies typically reject. These allorecognition phenomena play a fundamental role both modulating the nature and outcomes of intraspecific competitions for space, and preserving the genetic integrity of the colony. Invertebrate allorecognition has been recognized for over a century but has gained increasing attention only recently as a possible ancestor of the vertebrate immune system. Despite intense efforts, the genes and molecules controlling the response have not been identified in any colonial invertebrate. We have developed inbred and congenic lines of the colonial hydroid Hydractinia symbiolongicarpus (Cnidaria; Hydrozoa). In these lines, allorecognition responses were explained by a simple dose-dependent interaction between two linked allorecognition loci. AFLP markers co-segregating with fusibility were identified by bulk segregant analysis, and mapped using a test-cross population of 490 individuals. The resulting map circumscribed the allorecognition complex, ARC, at 3.4-cM. This map represents the basis for isolating by positional cloning the hydroid allorecognition loci.