Worm Breeder's Gazette 12(5): 65 (February 1, 1993)
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.
We are interested in how genes regulate the contractile activity of the pharynx to bring about efficient trapping and intake of bacteria. eat-4 seems to participate in the fine tuning of pharyngeal muscle contraction and relaxation. Worms with eat-4 mutated have partial contractions of the corpus and slow relaxations of the corpus as well as terminal bulb. As a consequence, mutant worms are unable to swallow bacteria efficiently. They are pale, slow growing and produce smaller broods (Avery 1993, Genetics, in press). No other phenotypes have been observed.
We have four alleles of eat-4 ,with ad572 being the strongest. The phenotype of eat-4 mutants is probably due to lost-of-function because all four alleles are fully recessive; ad572 / ad572 / qDp3 is wild type; and ad572 / qDf2 is Eat. We suspect that ad572 may be a null since ad572 / qDf2 does not seem to be more Eat than ad572 homozygote. In addition, new alleles of eat-4 have been isolated at high frequency (2 / 2653 EMS mutagenized chromosomes) in a non-complementation Fl screen. This screen did not bias towards viable mutants.
We believe that eat-4 is in the cosmid ZK512 based on three lines of evidence. First, eat-4 has been mapped between unc-32 and emb-9 by 3-point-crosses. Moreover, since eat-4 is uncovered by qDf2 and since qDf2 has its left breakpoint in glp-1 (Austin et al 1989. Development Suppl: 53), eat-4 should be between glp-1 and emb-9 on LGIII. Second, we have shown that ZK512 can rescue two eat-4 mutant alleles by germ-line transformation. Third, we have detected an RFLP (probably an insertion) in ad572 by Southerns probed with ZK512 .The restriction pattern is changed back to the wild type in an ad572 intragenic revertant. ( ad572 reverts at a low frequency (<1 in ~6800)).
ZK512 has recently been sequenced by the C. elegans genomic sequencing project. (Trevor Hawkins kindly provided us with the sequence). Using the GENEFINDER program, we searched for potential genes around the segment in which the RFLP was detected. We found a candidate gene which does not seem to have any significant homology with known proteins.
It is intriguing that eat-4 affects both contraction and relaxation. Since the strongest mutant has no phenotype outside of the pharynx, we think that it probably is not a house-keeping gene. We are continuing the molecular analysis of eat-4 to find out if it indeed corresponds to the locus found by GENEFINDER.