When coral colonies meet one another on the reef, they have two options: merge into a single colony or reject each other and aggressively compete for space. Now, a report in the March 19th Current Biology, a Cell Press publication, has found a gene that may help to decide that fate.
"We have identified a gene that controls how a colonial animal recognizes a member of its own species based on cell-cell contact," said Leo Buss of Yale University. "The ability to recognize individuals implies a capacity to categorize such encounters and, in this case, it allows colonies to discriminate between those individuals with which they will fuse or fight."
The researchers made their discovery by studying a colonial cnidarian called Hydractinia symbiolongicarpus in the laboratory. (Cnidarians are most familiarly represented by corals, sea anemones and jellyfish.) Perhaps best known to Atlantic basin and western Pacific beachcombers as the distinctive white fuzz growing on the top of hermit crab shells, Hydractinia have become a model for scientific exploration of such so-called allorecognition phenomena, which define self versus non-self.
Despite the ubiquity of allorecognition in colonial organisms and its ecological and evolutionary importance, its molecular basis had not been thoroughly defined. Such interactions in nature are also of interest because of their resemblance to those that occur in pregnancy and following organ transplantation.
Now, Buss, Stephen Dellaporta and their interdisciplinary colleagues have identified a key invertebrate allorecognition gene. The gene they identified appears to encode a transmembrane receptor expressed in all tissues capable of allorecognition. It also includes a hypervariable domain and exists in many different varieties that predict how Hydractinia colonies will interact with one another, they show. The gene sequence is most closely related to the immunoglobulin (Ig) superfamily of prote
|Contact: Cathleen Genova|