Evidence that the Drosophila olfactory mutant smellblind defines a novel class of sodium channel mutation.

The smellblind (sbl) gene of Drosophila is associated with olfactory defects, and the paralytic (para) gene encodes a voltage-gated sodium channel. sbl and para have similar genetic map positions, many combinations of sbl and para mutations fail to complement, and two sbl mutations contain molecular lesions within the para transcription unit. sbl mutations also behave like para mutations in that they are enhanced by the mutation no action potential temperature-sensitive (mlenapts1). The simplest interpretation of these results is that sbl and para are the same gene. Two sbl mutations produce olfactory defects not characteristic of classic sodium channel mutations and do not show typical heat-sensitive paralysis, suggesting that these sbl mutants define a novel class of sodium channel mutation.