Abstract
The activation of C. elegans spermatids to crawling spermatozoa is affected by a number of genes including spe-47. Here, we investigate a paralog to spe-47: spe-50, which has a highly conserved sequence and expression, but which is not functionally redundant to spe-47. Phylogenetic analysis indicates that the duplication event that produced the paralogs occurred prior to the radiation of the Caenorhabditis species included in the analysis, allowing a long period for the paralogs to diverge in function. Furthermore, we observed that knockout mutations in both genes, either alone or together, have little effect on sperm function. However, hermaphrodites harboring both knockout mutations combined with a third mutation in the him-8 gene are nearly self-sterile due to a sperm defect, even though they have numerous apparently normal sperm within their spermathecae. We suggest that the sperm in these triple mutants are defective in fusing with oocytes, and that the effect of the him-8 mutation is unclear but likely due to its direct or indirect effect on local chromatin structure and function.
Highlights
Sperm cells generally face a brief life of intense competition to realize their goal of fertilizing an oocyte
Phylogenetic analysis indicates that the duplication event that produced the paralogs occurred prior to the radiation of the Caenorhabditis species included in the analysis, allowing a long period for the paralogs to diverge in function
Once a signal is received, the spermatids undergo rapid wholesale cellular reorganization that involves an influx of cations [4], a brief elevation in pH [5], the release of intracellular Ca2+ [6,7,8], induction of a MAPK cascade [9], and polymerization of major sperm protein (MSP) and fusion of the membranous organelles
Summary
Sperm cells generally face a brief life of intense competition to realize their goal of fertilizing an oocyte To have success, they must execute with extreme efficiency. They must activate at precisely the right moment, locomote with haste using chemotaxis to guide them to the fertilization site, and fuse with an oocyte as quickly as possible. All this is required of a cell stripped of its ability to express its genome, in most cases surviving only on the meager stores within its tiny volume. Once a signal is received, the spermatids undergo rapid wholesale cellular reorganization that involves an influx of cations [4], a brief elevation in pH [5], the release of intracellular Ca2+ [6,7,8], induction of a MAPK cascade [9], and polymerization of major sperm protein (MSP) and fusion of the membranous organelles
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