In the previous gazette (WBG: 11 (3),
p69), we have described isolation of axon growth mutants using the FITC dye staining method of Hedgecock et al. (1985), in the mutator strain RW7097. In particular we mentioned a strain SQ141, that lacked staining of phasmid neurons PHA and PHB in the adult hermaphrodites. This mutation has been mapped on linkage group IV close to
dpy-13, prompting us to complement SQ141 mutation with
osm-3 and
osm-4 (aka
daf-10) that were reported lacking FITC staining of PHA and PHB neurons (Perkins et al. 1986). SQ141 complements
osm-4(aka
daf-10), but it does not complement
osm-3(
p802) allele. However, the
osm-3(
p802) phenotype, is different from the reported description of the
osm-3(
p802) in that we find about 35% hermaphrodites show weak staining of one or two pairs of amphid neurons. The phasmid neurons in
osm-3(
p802) adult hermaphrodites do not stain; but about 26%
osm-3(
p802) males show staining of the phasmid neurons. We also observe weak staining of one or two pairs of amphid neurons in about 60%
osm-3(
p802) males. We have isolated another strain SQ160, from RW7097, that fails to complement the phasmid phenotype of SQ141 and
osm-3(
p802) in adult hermaphrodites. For complementation studies, we have only considered the PHA and PHB staining pattern in the adult hermaphrodites, in appropriately marked crosses to distinguish the self progeny from the cross progeny, as the FITC staining of PHA and PHB in males can not be used to score complementation two factor cross data between
osm-3 and
dpy-13 places the two mutations 2.2% apart (
dpy-13(
e184) 5/110 SQ141). The
osm-3 mutations in SQ141 and SQ160 strains have been backcrossed with N2 males ten times, to recover these mutations in Bristol background using appropriate recombinant strains with
osm-3 and
dpy-13, and
osm-3 and
unc-17, we find a 3.9 kb band on Southerns of DNA isolated from different strains, with a Tc1 probe, that is associated with the
osm-3 mutation, and is absent in strains lacking the
osm-3 alleles. Experiments are in progress to further characterize and clone the
osm-3 specific DNA band. Mutants in
osm-3 were first isolated by Joe Culotti and Richard Russell (1978), by a simple behavioral assay in which these chemosensory mutants fail to avoid high (4M) concentrations of NaCl; and were later tested for a variety of behaviors (Perkins et al. 1986) . We have performed these assays on SQ141 and SQ160 animals, and their behaviors are typical of other
osm-3 alleles