Worm Breeder's Gazette 10(3): 137

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.

Informational Suppression by Male-abnormal Mutations: New Names, New Data

Jonathan Hodgkin

Figure 1

As previously reported (WBG 10-1: 112, 10-2: 30, etc.) mutations at 
six different loci act as allele-specific suppressors of mutations in 
a variety of genes: tra-2, unc-54, etc.  These 
mutations also have characteristic morphological effects on the 
anatomy of the adult male tail and, to a lesser extent, of the 
hermaphrodite vulva.  For this reason they have hitherto been assigned 
to the mab (male abnormal) gene category: mab-1, 
ed) and mab-12 through mab-16 (unpublished).  
However, they exhibit such a distinctive set of common properties that 
it has been decided (with the agreement of Andy Papp, Victor Ambros, 
Rock Pulak and Phil Anderson, who have been responsible for isolating 
most of these suppressor mutations) to assign them to a new gene 

smg, standing for Suppressor, Morphological effect on Genitalia, 
with the assignments as follows.
[See Figure 1]
An additional reason for this change is that it is more convenient, 
and less misleading, to refer to suppressible alleles as 'smg-
suppressible' than as 'morphomab-suppressible' .
The number of genes for which smg-suppressible alleles have been 
identified continues to increase.  Jim Rand (personal communication) 
has identified an allele of cha-1/unc-17 which is efficiently 
suppressed by at least some of the smg mutations.  Also, Andy Fire 
noticed that an old friend, dpy-5(e61), appeared to be partly 
suppressed by smg-2.  I have confirmed this: all six standard smg 
mutations act as recessive partial suppressors of e61, leading to a 
significant increase in length of about 30% (e.g.  adult wild type 
1460  , e61 760  , e1228 e61 1010  ).  The suppression is allele-
specific, consistent with the general pattern of smg effects, because 
two other alleles of dpy-5, e565 and e907, show no increase in length 
in the presence of smg-2(e2008).
A paradoxical enhancement effect has also been observed with dpy-5.  
The e61 allele is slightly semidominant, so e61/+ animals are very 
slightly shorter than wild type, but the effect is slight.  However, 
e61/+ animals which are also homozygous for a smg mutation are dumpy!  
This is the case for smg-1, -2, -3, and -4, at least; the other two 
have not been tested.  Thus, the smg's enhance one dose of e61 and 
suppress two, a disgustingly zesty situation.  It is conceivable that 
the enhancement is acting via the wild type allele, not the e61 allele,
in e61/+.  If this were the case, heterozygotes of the other alleles, 
for example e907/+, should also show enhancement by smg's, but this 
does not seem to be so.

Figure 1