Apparent involvement of a beta1 type integrin in coral fertilization

Integrins are involved in a wide variety of cell adhesion processes, and have roles in gamete binding and fusion in mammals. Integrins have been also discovered in the scleractinian coral Acropora millepora (Cnidaria: Anthozoa). As a first step toward understanding the molecular basis of fertilization in corals, we examined the effect of polyclonal antisera raised against recombinant coral integrins on gamete interactions in A. millepora. Antiserum raised against integrin betacn1 dramatically decreased the binding of Acropora sperm to eggs and significantly decreased fertilization rates relative to preimmune serum and seawater controls. However, the antiserum against AmIntegrin alpha1 did not affect significantly either sperm-egg binding or fertilization. One possible explanation for this is that AmIntegrin alpha1 may preferentially mediate interactions with RGD-containing ligands, whereas mammalian alpha6 integrin (which is most directly implicated in gamete interactions) preferentially interacts with laminin-related ligands. Our results suggest that beta1 type integrins are involved in the fertilization process in Acropora and that some functions of these molecules may have been conserved between corals and mammals.