2 GRASSES OF OLFACTORY RECEPTORS IN XENOPUS-LAEVIS

Xenopus laevis possess a gene repertoire encoding two distinct classes of olfactory receptors: one class related to receptors of fish and on e class similar to receptors of mammals. Sequence comparison indicates that the fish-like receptors represent closely related members of onl y two subfamilies, whereas mammalian-like receptors are more distantly related, most of them representing a different subfamily. The fishlik e receptor genes are exclusively expressed in the lateral diverticulum of the frog's nose, specialized for detecting water-soluble odorants, whereas mammalian-like receptors are expressed in sensory neurons of the main diverticulum, responsible for the reception of volatile odors .