Worm Breeder's Gazette 2(2): 38

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.

Osmotic Avoidance Defective Mutants of C. elegans

J.G. Culotti, R.L. Russell

Seven independently derived mutants of C.  elegans have been 
isolated for their inability to avoid high concentrations of NaCl or 
fructose at neutral pH.  Behavioral characterization of double-
backcrossed versions of these mutants reveals that (1) mutants 
isolated for their inability to avoid fructose are also unable to 
avoid NaCl and vice versa (the mutants are therefore believed 
defective in a single response to conditions of high molarity and 
hence are called 0smotic mutants), (2) all of the mutants are 
partially chemotaxis defective, and (3) all of the mutants are able to 
follow isothermal lines in a thermal gradient.  With one exception, 
all of the chemotaxis and thermotaxis mutants previously isolated in 
this laboratory avoid high concentrations of NaCl essentially as does 
wild type.  The exception is chemotaxis mutants of the complementation 
group tax-1 which avoid high concentrations of NaCl less well than 
wild type.  These mutants represent a new complementation group 
required for the osmotic response.
Genetic studies indicate that each of the mutant strains carries a 
single recessive mutation responsible for the osmotic phenotype.  
Three of the mutants are x-linked and four are autosomal.  Only two of 
the mutants (JC-8 and JC-16, both X linked) are in the same 
complementation group.  All seven of the mutants have been mapped to 
regions on four of the six C.  elegans linkage groups.  The JC-8, JC-
16 complementation group has been precisely mapped to the right end of 
the X chromosome 6.4 map units to the right of unc-3.Preliminary 
serial section EM results obtained by Dr.  R. Ware (personal 
communication) suggest that a limited number of neurons in the 
anterior sensory nervous system are affected in mutant JC-11.  The 
ciliated sensory endings of the 'lateral submedial' sensory neurons (
'cephalics') are completely disorganized in this mutant even though 
their structurally similar neighbors the 'medial submedial' neurons (
'outer labials') are not at all affected in this respect.  The lateral 
submedial sensory neurons have been shown to contain dopamine (Sulston 
et.  al., 1975).  A quantitative radioenzymatic assay for 
catecholamines is now being used to determine dopamine levels in the 
osmotic avoidance defective mutants.