Worm Breeder's Gazette 13(3): 67 (June 1, 1994)

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.

Toward molecular cloning of tax-4 ,a gene necessary for both thermo- and chemotactic responses of C. elegans

Hidetoshi Komatsu, Ikue Mori, Yasumi Ohshima

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Athermotactic mutations, which cause animals to move almost randomly on a thermal gradient, are always coupled with chemotactic defects.(1) These mutations so far fall into 4 complementation groups, one of which defines tax-4 gene ( p678 , ks11 , ks28 ).All 3 tax-4 mutants are athermotactic and defective in chemotaxis to NaCl, and at least one mutation, p678 ,was recently found to cause abnormal responses to volatile odorants.(2) These tax-4 mutants, however, seem to be normal for osmotic avoidance response and dye-fillings of amphid sensory neurons.

To investigate the molecular bases underlying these multiple taxis defects, we have begun to clone tax-4 .

First, tax-4 ( ks11 )was mapped to linkage group III. Further 3-factor crosses demonstrated that tax-4 ( ks11 )lay between unc-32 and unc-69 .At that point, we attempted to rescue the tax-4 mutant using 40~50 cosmids covering the whole unc-32 - unc-69 interval. However, this strategy was unsuccessful: we failed to identify any cosmid, which could rescue tax-4 mutant phenotype.

We then decided to genetically map the locus more precisely. A genetic mapping based on polymorphic Tc1 sites(3) showed that tax-4 ( ks11 )maps to the region left of stP127 and to the right of mgP21 . The following 3-factor crosses indicated that tax-4 maps to the region between unc-32 and emb-9 ,and possibly near or right of lin-12 .From tax-4 ( ks11 )/ unc-32 emb-9 hermaphrodites, 9/16 Unc non-Emb recombinant progeny segregated tax-4 .From tax-4 ( ks11 )/ unc-32 lin-12 hermaphrodites, 2/2 Unc non-Lin recombinant progeny segregated tax-4 .From tax-4 ( ks11 )/ dpy-19 eP6 eP7 unc-50 hermaphrodites, 1/11 Dpy non-Unc recombinant progeny segregated tax-4 .

While we are in the process of re-starting injection experiments using cosmids and YACs, we still want to narrow down the tax-4 region as much as possible using RFLPs and visible markers. We are aware of the fact that some types of genes are not able to be cloned easily by rescue experiments.

Literature Cited:

(2) Bargmann et. al. (1993), Cell 74:515

(3) Williams et.al. (1992), Genetics 131 :609

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