Worm Breeder's Gazette 10(1): 94

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.

Isolation and Characterization of Revertants of emb-1(hc57)

K. Nishiwaki and J. Miwa

Temperature-sensitive maternal mutations in the emb-1 gene cause 
defects in the migration and fusion of pronuclei and in the 
pseudocleavage of a fertilized egg.  The gene function is required 
within a short period around fertilization.  We are isolating and 
characterizing revertants of emb-1 mutations to investigate emb-1 gene 
function and to analyze events around fertilization.  With EMS 
mutagenesis we have independently isolated 4 revertants from emb-1(
hc57) III, which can grow at the nonpermissive temperature of 25 C.  
Two of them were shown to be dominant mutations and mapped to linkage 
group I and II.  Two others were semidominant and mapped to linkage 
group III.  The former two revertants were further characterized to 
show that maternal expression of the mutations was necessary and 
sufficient for the suppression of emb-1(hc57).  Cytological 
observation has revealed that these revertants in the hc57 background 
exhibited weak pseudocleavage and lacked male pronuclear migration at 
25 C.  This suggests that the restoration of the emb-1 gene function 
is incomplete and that normal pseudocleavage and male pronuclear 
migration are not absolutely necessary for the development of C.  
elegans.  DAPI staining of the hc57 mutant detected more stained 
materials in the female pronucleus than in the male pronucleus and no 
polar bodies in fertilized eggs.  With rhodamine-phalloidin staining, 
we found that the hc57 mutant exhibited rapid aggregation of 
microfilaments after fertilization at 25 C we are looking into a 
possible defect in meiosis after fertilization.