Worm Breeder's Gazette 10(3): 90

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

"Sixless" Males

Scott E. Baird and Scott W. Emmons

We have isolated an EMS-induced mutation, bx23, that specifically 
affects the development of sensory ray 6 in C.  elegans males.  In 
mutant individuals, the morphologically thickened ray 6 is missing, 
and in its place there is an ectopic ray that is located adjacent to, 
and is morphologically similar to ray 4.  In most animals, the ectopic 
ray and ray 4 are fused on both sides.  This phenotype is reflected in 
L4 males where the distinctive ray 6 papilla is missing and an ectopic 
papilla is present adjacent to the ray 4 papilla.  bx23 does not 
affect male mating efficiency and no mutant phenotypes have been 
observed in bx23 hermaphrodites.
The bx23 mutation has been mapped to approximately position +4.8 of 
linkage group X.  No male specific defects have been described for any 
genes in this region.  Thus, it appears that the bx23 mutation 
identifies a new gene that is required specifically for the 
differentiation of ray 6.
The V6 cell lineage has not been determined in bx23 males, and 
therefore two simple explanations are possible to explain the mutant 
phenotype.  First, it is possible that the V6 lineage is not affected 
by bx23.  In this case, bx23 males would be defective in both the 
posterior migrations of the ray 6 precursor cell (R6) and its 
descendants, and in the differentiation of the ray 6 B neuron.  
Alternatively, a lineage defect could result in the failure of the R6 
lineage and the recruitment of an ectopic ray from a different branch 
on the V6 lineage.  For example, a ray cell group could be recruited 
from the anterior sister of the ray 4 precursor cell, V6.pppaa.