Worm Breeder's Gazette 11(4): 63
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.
The fem-3 gene is required for specifying male development. In XO males, fem-3 is active in the soma and germline to specify male somatic tissues and sperm. In XX hermaphrodites, fem-3 must be inactive in the soma to allow female development. In the XX germline however, fem-3 is active in larvae to promote a brief period of spermatogenesis, and then it must be turned off in adults to allow oogenesis. How is regulation of fem-3 achieved? To determine whether specific regions of the fem-3 gene impart control of its expression, we constructed reporter gene plasmids that contain the E. coli lacZ coding region flanked by fem-3 5' and 3' sequences. These plasmids were then coinjected with rol-6 to generate transformed lines. Although these lines had inconsistent patterns of lacZ expression, they all exhibited an interesting phenotype: feminization of the germline (or Fog). Both XX and XO transgenic animals make only oocytes (in 85-98% of the animals), but show normal sexual development of the soma. Thus, these lines behave as if they have lost fem-3 function specifically in the germline. Deletion analysis has identified a 190 base region of the 5' untranslated region (5' UTR) that is necessary for inducing the Fog phenotype. These results suggest that excess 5' UTR sequences may sequester a regulatory factor that is necessary for fem-3 expression in the germline. Several observations suggest that it may be RNA containing the 5' UTR that causes the FOG phenotype. (1) A plasmid carrying the 5' UTR alone is not sufficient; 5' flanking sequence is required for full activity. (2) The complete Fog effect depends on the sense orientation of the 5' UTR relative to 5' flanking sequences. (3) In preliminary experiments, we have found that the levels of endogenous fem-3 RNA are not substantially altered in Fog transgenic animals. Therefore, it is possible that a regulatory factor binds fem-3 mRNA in the 5' UTR to stimulate translation (directly or indirectly) of the fem-3 protein, and the presence of excess 5' UTR prohibits this interaction. Other explanations (e.g. titration of DNA-binding factor, or anti-sense RNA) have not been completely ruled out.