Worm Breeder's Gazette 9(1): 42

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.

A Genetic Analysis Of An RNA Polymerase II Subunit Gene (ama-1 IV) In C. elegans

T.M. Rogalski and D.L. Riddle

Figure 1

In the last issue of the WBG (Vol.  8, No.  3) we described the 
isolation and identification of six 'lethal' alleles of ama-1 IV, a 
gene encoding a subunit of RNA polymerase II (Sanford, Golomb and 
Riddle, J.  Biol.  Chem.  258:12804-12809, 1983).   The six ama-1 
mutations arrest development at various stages when homozygous.  Two 
are embryonic lethals, three are adult steriles and the remaining 
mutation is sub-lethal (i.e.  m251 hermaphrodites grow slowly and have 
a reduced brood size).  In addition, one of the sterile mutations is 
temperature-sensitive.  At 15 C and 20 C hermaphrodites homozygous for 
m238 produce some progeny (20) while at 25 C they are sterile.  We are 
currently screening for additional mutations affecting the ama-1 gene 
and have isolated three new alleles, all of which are early larval 
The two embryonic lethal alleles of ama-1 have been further 
characterized by observing arrested embryos obtained from dpy-13(e184)
ama-1   (m118mx)/+++ hermaphrodites using Nomarski interference-
contrast microscopy.  Both of these mutations appear to arrest 
development late in embryogenesis.  Although the actual stage varied 
with both alleles, most of the embryos characterized were blocked 
during morphogenesis, between the lima bean and pretzel stages.
A genetic characterization of the LGIV region around amn-1 has 
identified 16 essential genes in an interval of 4.5 map units (see the 
accompanying Genetic Map).  Three of these genes are represented by 
more than one allele (let-272 and let-275 have two alleles; let-276 
has six).  In addition, this analysis has also identified three gamma-
ray-induced deficiencies that include ama-1.  The smallest deficiency, 
mDf4, is approximately 1.5 to 2.0 map units in Iength and its Ieft 
endpoint is located between let-278 and ama-1, an interval of 0.1 map 
units.  Nine of the essential genes are included in mDf4.  The mDf4 
deficiency has been used to identify a recombinant DNA clone carrying 
the ama-1 gene (Bird and Riddle, this issue).
The mutations that define the 16 essential genes around ama-1 
exhibit a wide range of lethal phenotypes; from embryonic to maternal-
effect.  Eight of the genes are represented by sterile mutations, and 
all but one of these are located to the right of dpy-13.[See Figure 

Figure 1