Worm Breeder's Gazette 9(1): 72
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 showed previously that vitellogenin gene transcripts can be easily detected in intestinal cells of hermaphrodites but not males, by in situ hybridization to dissected intestines using a cloned vit-5 probe (from T. Blumenthal), which cross-hybridizes to four other members of a multigene family in addition to vit-5. Among triploid intersex animals (3A;2X plus a large X duplication), about twenty percent show mosaic intestines, with some cells that hybridize and some that do not. The patterns of positive and negative cells are nonrandom and inconsistent with a lineage-related mechanism of intestinal-cell sex determination based on patterns predicted from the known E lineage. Instead, all mosaics show eight to sixteen contiguous positive cells at the anterior end and negative cells throughout the remaining observable portion of the intestine, implying positional influences on the decision to express or not to express vitellogenin genes (Schedin and Wood, 1985 C. elegans Meeting Abstracts, p. 102). In some mosaic intestines the vit-5 hybridization level is not uniform in all positive cells, but shows a gradient of intensity, with anterior positive cells hybridizing more strongly than posterior positive cells. The variable hybridization could be due to more individual members of the vit-5 gene family being expressed anteriorly, or to variable levels of expression for one or more members of the family. Probes specific for individual family members are not available. Therefore, to ask whether a single vitellogenin gene could show variable expression, we analyzed intestines of intersexes using a single-gene vit-6 probe (from T. Blumenthal), which does not crosshybridize with the vit-5 gene family under our conditions. We found that vit-6 expression shows patterns similar to those seen for expression of the vit-5 gene family. Animals with mosaic intestines all show an anterior region of contiguous positive cells, and a posterior region of contiguous negative cells. The hybridization sometimes appears uniform over the positive cells and sometimes shows the same sort of anterior-posterior gradient of intensity seen with the vit-5 probe. We conclude that the level of expression of vit-6, a single-copy gene, can be variable in mosaic intestines. To determine whether the vit genes are coordinately regulated in intersex mosaics, we are currently doing double labelling experiments with a biotin-labelled vit-5 probe and a 35S-labelled vit- 6 probe.