Worm Breeder's Gazette 7(1): 69

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Benomyl-resistant Mutants

M. Chalfie

Figure 1

The antimicrotubule drug benomyl strongly affects the growth of C.  
elegans.  Wild-type animals grow slowly and become extremely 
uncoordinated in the presence of the drug (Chalfie and Thomson, J.  
Cell Biol., in press).  The unc character of the animals correlates 
with a loss of nerve processes in the ventral cord (Table 1).  
Interestingly, the drug does not affect the outgrowth of the wild-type 
touch cells.  (The touch cells microtubules have 15 protofilaments; 
those in the ventral cord cells have 11-protofilaments).  However, 
benomyl does prevent the outgrowth of the touch cells in mec-7 mutants 
(here the touch cells have 11 protofilaments).  
Benomyl-resistance has been used to identify alpha-tubulin mutants 
in Aspergillus (Sheir-Neiss et al., Cell 15: 639-647, 1978).  In an 
attempt to isolate similar mutants in C.  elegans, I mutagenized N2 
stocks and looked for F2 animals that were non-Unc in the presence of 
benomyl.  Two resistant strains have been isolated so far.  The first 
has a mutation e1880 (ben-1) that maps to the left of linkage group 
III in the region of mec-12 (from which it is separable).  This mutant 
is dominant, and animals carrying the allele have the normal number of 
ventral cord processes even in the presence of benomyl (Table 1).  The 
ben-1 mutation also conveys resistance to benomyl for the mec-7 touch 
cells, i. e.  these cells grow out normally in the presence of the 
drug in the ben-1;   No differences have been 
identified in the tubulin pattern in 2-D gels of ben-1 and wild type.  
The second mutation-e1881, is weakly semidominant, but has not been 
fully characterized.  Isolation of additional resistant mutants and 
revertants and characterization of the C.  elegans tubulin genes are 
in progress.
[See Figure 1]

Figure 1