Worm Breeder's Gazette 3(2): 39

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.

Theoretical Worm Biology: A Possible General Method for Obtaining Overproducing Mutants

J. Lewis

What good is an informational suppressor that doesn t work very well?
It occurred to us that reversion of a mutant doubly homozygous for a 
suppressible allele and an inefficient suppressor might yield two 
types of revertants involving the suppressor (plus unrelated types to 
be sorted out as below).  One type might involve mutations making the 
suppressor itself act more efficiently.  With a suppressor line sup-5(
e1464), more efficient suppression would probably be lethal and 
inherently counterselected.  Reversion might also be achieved by a 
mutation causing overproduction of mRNA at the suppressed locus.  If 
the suppressor produces 1% of wild-type function cranking away on 1 x 
mRNA, working at the same efficiency on 100 x mRNA it might produce 
100% of wild-type function.  Hopefully, when any such overproducing 
mutation was put in a wild-type background, it would produce 100 x as 
much of the wild-type gene product.
The attractiveness of this method is that the suppressor itself 
provides a means of characterizing revertants without the need to 
biochemically identify the gene product.  In a more classical 
reversion of a leaky mutant, same site revertants would be very hard 
to distinguish genetically from closely linked regulatory mutants (e.g.
, promoter-up mutants in bacteria).  With the above method, true 
regulatory mutants would be dependent on the presence of the 
suppressor, whereas same site revertants would not be.  The original 
mutant phenotype should be rescuable by the backcrossing for any 
revertant dependent on the presence of the suppressor.  Mutations 
making the suppressor generally more efficient, if such were viable, 
could be detected by testing the suppressor against poorly 
suppressible alleles at unrelated genetic loci.  Overproducing 
mutation reverting one suppressible allele should also work on other 
suppressible alleles at that locus but generally not function on 
nonsuppressible alleles.  The suppressor test could be used to 
evaluate possible overproducers initially isolated by other means.  It 
will be a while before we can thoroughly test this idea on levamisole-
resistant mutants and the idea may or may not work for any particular 
set of loci.  So we toss the idea out in the hope that it may prove 
generally useful.