Worm Breeder's Gazette 12(2): 63 (January 1, 1992)
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 investigating two trimethylpsoralen-induced non-maternal mutations, ct224 and ct281 ,which define a complementation group temporarily termed " nob-2 "and result in hatching L1 swith a fairly normal anterior and a grossly defective (nob-like) posterior; these animals die in a day or two. The first visible defect is abnormal arrangement of the 8 E cells at approximately the 200 cell stage. The mutations map to LG III between unc-79 and dpy-17 ,and fail to complement the male ray phenotype of pal-1 ( e2091 ),obtained from C. Kenyon(1). ct224 shows slightly more severe defects than ct281 .We have probed Southern blots with fragments from three nested genomic subclones containing pal-1 sequences (see diagram), generously provided by D. Waring and C. Kenyon, and find polymorphisms associated with both alleles. ct224 deletes approximately 4kb, removing the 3' pal-1 exon and part or all of the next exon containing the homeobox sequence ceh-3 (2). ct281 deletes approximately 1 kb, and removes only the 3' exon.
[See Figure 1]
Since these are deletions, we are still faced with the possibility that they disrupt a second gene lying close to or overlapping pal-1 .Northern blots using pWPK6 probes identify two transcripts of approximately 1.25 and 1.45 kb (the pal-1 cDNA is 1.3 kb and presumably full-length, since the 5' end contains part of the splice leader sequence(3)), present in RNA from eggs and mixed population worms, and at low levels in L1 RNA. An additional transcript (800 bp) is identified by probes just 3' to pWPK6 .In rescue experiments, injection of pWPK6 into ct224 unc-32 dpy-18 / qC1 gave Unc Dpy F1 sthat produced only Nob progeny, indicating complementation, but we have not yet obtained a transformed line with any of the plasmids or the cosmid W O5E6 ,which covers this region. Although more experiments will be required to rule out the possibility that the nob-2 mutations affect an overlapping gene, these results suggest that they are pal-1 null mutations. Thus there may be an embryonic posterior patterning function for this gene, which postembryonically mediates cell communication in the male tail, possibly by regulating the homeobox gene mab-5 (1,3).The pal-1 homeobox has similarities to the Drosophila gene caudal and the mouse gene cdx-1 ,both of which also appear to be involved in organization of posterior embryonic endoderm.
2. Burglin et al., 1989, Nature 341: 239-243
3. Waring & Kenyon, 1991, Nature 350: 712-715.