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 d efects, and the paralytic (para) gene encodes a voltage-gated sodium c hannel. sbl and para have similar genetic map positions, many combinat ions of sbl and para mutations fail to complement, and two sbl mutatio ns contain molecular lesions within the para transcription unit. sbl m utations also behave like para mutations in that they are enhanced by the mutation no action potential temperature-sensitive ( mle(napts1)). The simplest interpretation of these results is that sbl and para are the same gene. Two sbl mutations produce olfactory defects not charac teristic of classic sodium channel mutations and do not show typical h eat-sensitive paralysis, suggesting that these sbl mutants define a no vel class of sodium channel mutation.