Worm Breeder's Gazette 9(3): 46

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.

Suppressors of bli-6(mn4) IV

M. Winter and R. Herman

The mutation mn4, which was identified among the progeny of X-ray 
treated males, confers a blistered phenotype. The mutation is dominant 
to wild-type with 100% penetrance. The reference allele for bli-6 IV 
is sc16, which is recessive to wild type. Meredith Kusch has mapped 
mn4 and another dominant mutation, sc74, close to sc16; and Park and 
Horvitz (1986, Genetics 113:821) have mapped their EMS-induced 
dominant mutation n776 very near to sc16. Thus it appears that bli-6 
IV is represented by one recessive and three dominant alleles.
We have identified 44 independent EMS-induced revertants of mn4. All 
are extragenic suppressors, and they fall into two general classes: 23 
are recessive dumpy mutations and 21 have wild-type morphology. All 
but one of the dumpy mutations have been assigned to known dpy genes, 
as follows: 1 allele of dpy-1 III, 3 alleles of dpy-3 X, 4 alleles of 
dpy-4 IV, 3 alleles of dpy-5 I, 3 alleles of dpy-7 X, 4 alleles of dpy-
8 X, 1 allele of dpy-9 IV, 1 allele of dpy-10 II, and 2 alleles of dpy-
13 IV. Not all dumpy mutations suppress mn4. For example, dpy-6(e14) X,
dpy-17(e164) III and dpy-18(e364) III do not suppress mn4 (and no 
suppressing alleles of these genes have been identified in our 
reversion screen), but dpy-5(e61) and dpy-1O(e128) do. All but three 
of the 23 dumpy mutations are recessive suppressors of mn4, i.e., 
animals of genotype dpy/+; mn4/+ are Bli non-Dpy. In the other three 
cases, however, dpy/+; mn4/+ animals are non-Bli non-Dpy. The three 
dominant suppressors are alleles of dpy-4,  
of these genes, we have at least one recessive suppressor allele; thus 
in each case the effect is allele specific, not gene specific. An 
incidental point about another dpy: Claire Kari has shown that the 
previously unmapped dpy-12(e182) is an allele of dpy-3.Analysis of the 
wild-type suppressors has not progressed as far, although most have 
been outcrossed at least twice. Seven of the 21 suppressors are 
dominant, by the criterion that mn4/+; sup/+ hermaphrodites are non-
Bli (males of this genotype are sometimes blistered). Three of the 
recessive wild-type suppressors appear to be X-linked (mn4/+; sup/O 
males are non-Bli) and fail to complement each other. We note that 
Kusch and Edgar (C. elegans Newsletter 9, no. 1. p.51) previously 
identified a wild-type suppressor of bli-6(sc73) which mapped to LGV 
and which also suppressed bli-6(sc16).We have put mn4 into a TR679-
like background and identified a few spontaneous revertants. One is a 
dumpy, an allele of dpy-5 I, and we have a spontaneous revertant of it.

Alice Burton, who is a member of the Biology Department of St. Olaf 
College in Northfield, MN, is looking at the SDS-soluble cuticle 
proteins of wild-type and mutant animals on SDS polyacrylamide gels.