The
daf-21 (
p673) gene has been reported to encode the HSP90 homologue in C. elegans (Birnby DA et al., 2000). To study DAF-21 functions in C. elegans development, we used three different approaches of immunohistology, transgenic examination, and loss-of-function analysis. Immunohistological studies showed that DAF-21 was distributed in germ cells throughout the life cycle at 20. When worms were heat-shocked at 32 for two hours, in addition to the distribution in germ cells, DAF-21 was also localized distinctly in the perinuclear region of somatic cells. To define further the role of DAF-21 in germline development, we performed two different types of gloss-of-functionh analyses by using the RNAi method and the mutant Daf-21 (
p673). The RNAi experiment revealed several phenotypes in F1 animals born of the
daf-21 dsRNA-injected parental animal, which showed reduced fertility. Some F1 showed embryonic lethality and growth arrest at L1 and L2 stages, whereas some others that grew to be adults displayed defects in germline development, such as egg-lying abnormality, small brood size, and sterility. Using sterile F1 animals, we performed paternal rescue experiments by crossing them with wild-type males, and observed them to produce very few eggs. These results indicate that oocyte production in the F1 animals was suppressed or caused to be defective by
daf-21 dsRNA, suggesting an essential role of DAF-21 for C. elegans oogenesis. In another loss-of-function study with
daf-21 (
p673), we again performed paternal rescue of its reduced brood size by crossing the
daf-21 hermaphrodites with wild-type males and found that the reduced brood size was not rescued. Considering this together with the RNAi results, we interpret that DAF-21 plays a critical role in C. elegans germline development. To examine the roles of two 5f-UTR in the
daf-21 promoter region, we constructed transgenic animals wherein a GFP reporter gene was fused with various sites in the
daf-21 promoter region. The observation of the DAF-21 expression indicated that the second 5f-UTR is indispensable for both normal constitutive and heat-induced expression.