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.
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.