Worm Breeder's Gazette 7(1): 87
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.
Five absolute embryonic lethal mutant alleles showing a strict maternal effect (M,M: mutant animals produce no viable embryos after mating with N2 males), linked to dpy-10 II or unc-4 II, and carried as balanced heterozygotes were roughly mapped relative to the linked morphological marker and tested for suppressibility by sup-7(st5) X. The five alleles, all recovered following EMS mutagenesis, were ct1 and ct5 (isolated by John Laufer) and mn40, mn202, and mn203, obtained from R. Herman. Three of them, ct1 (2% to the right of dpy-10), ct10 (2% to the left of unc-4), and mn203 (about 2% from unc-4) were not suppressed; crosses of the corresponding balanced heterozygotes with sup-7 males gave no higher frequency of fertile morphologically marked F2 animals than expected from recombination. However, a balanced heterozygote carrying mn40 (1% to the left of unc-4) in similar crosses gave about 50% fertile F2 Unc progeny (1 to 50 viable embryos; unc-4mn40 homozygotes normally produce many defective embryos with <0. 02% viability). A balanced heterozygote carrying mn202 (22% to the right of unc-4) in crosses with sup-7 males carrying the suppressible allele dpy-18(e364) III gave about 40% fertile F2 Unc progeny as expected from recombination. Suppression was demonstrated by picking semiDpy unc-4mn202/+;dpy-18/dpy-18;sup-7/+ F2 hermaphrodites and showing that their nonDpy Unc progeny produced viable embryos, whereas their Dpy did not. Some semiDpy Unc progeny also produced viable embryos; the frequency was uncertain due to the difficulty of unequivocally distinguishing semiDpy from nonDpy and Dpy animals. These results show that both mn40 and mn202 are suppressible and suggest that both are suppressed marginally by one copy of sup-7 and better by two copies. Suppressed lethals (unc-4mn;sup-7), easily distinguishable from recombinants by their reduced fertility and slower development, were isolated from each of these crosses and shown by backcrossing to carry the lethal mn allele. The suppressed lethals can be maintained near 20 C but not at lower or higher temperatures; at 16 C sup-7 is lethal, and at 25 C it suppresses the mn alleles poorly. The genes defined by mn40 and mn202 must be transcribed during oogenesis. Neither mutant homozygote produces viable embryos following mating with sup-7 males, consistent with the possibility that the corresponding messages are also translated prior to fertilization. We are attempting to determine the translation period by temperature-shift experiments, taking advantage of the temperature- sensitive properties of sup-7. We are also using these mutants in attempts to detect transformation of worms with cloned suppressor genes introduced by microinjection.