Worm Breeder's Gazette 9(1): 80

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.

Mutants That Pump When Wild-type Worms Don't

L. Avery and B. Horvitz

We are studying pharyngeal pumping in order to understand the 
development and function of the nervous system that controls pumping.  
At the last worm meeting, we described a method for isolating mutants 
that pump under conditions in which wild-type worms don't.  Worms are 
suspended in liquid with microscopic iron particles; then the worms 
that have pumped iron are pulled out with a small magnet.  Using this 
selection we have isolated two different sorts of pumping mutants and 
are now characterizing them.
Well-fed wild-type worms pump very little in the absence of bacteria.
Three of our mutants do pump under these conditions, so we call them 
pumping constitutive.  One mutation, n1304, is a new allele of unc-31 
IV.  n1304 has a recessive Unc phenotype similar to that of unc-31(
e169), and e169 pumps constitutively.  The two alleles fail to 
complement for both phenotypes.  The remaining two mutants look normal 
in the dissecting microscope.
We also have one mutant that pumps in the presence of ivermectin, a 
drug that normally inhibits pumping and also prevents worms from 
growing.  (We thank Marty Chalfie for telling us about ivermectin.) 
Although the mutant was selected only for ability to pump in the 
presence of ivermectin, it also grows on plates containing ivermectin: 
perhaps the lethal effect of the drug is due entirely to its 
inhibition of pumping.  None of our pumping-constitutive mutants grows 
on ivermectin plates.