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[
Trends in Ecology & Evolution,
1999]
In a recent TREE news & comment, Gadagkar made some useful comments on LaMunyon and Ward's interesting study on sexual reproduction in nematodes. I think, however, that he - and LaMunyon and Ward - have confused the benefits of sex for species or demes with those for individuals or genes.
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[
Trends in Ecology & Evolution,
1999]
In a recent TREE news & comment, Gadagkar made some useful comments on LaMunyon and Ward's interesting study on sexual reproduction in nematodes. I think, however, that he - and LaMunyon and Ward - have confused the benefits of sex for species or demes with those for individuals or genes. For females and hermaphrodites (but not for species or demes), the twofold cost of sexual reproduction or producing males' in Maynard Smith's sense implies the cost of producing offspring that have only half of the hermaphrodite parent's genome set - not directly that of producing males. An offspring of a hermaphrodite Caenorhabditis briggsae inherits half, not more, of each parental genome set. The hermaphrodite parent still pays the two fold cost of sexual reproduction in the same way as
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[
1983]
In 1974, Sydney Brenner published an elegant paper that described the genetic system of Caenorhabditis elegans and led to its use in research on a wide variety of topics, including aging (Brenner, 1974). Its small size (1mm as an adult) and determinate cell lineage has allowed a description of the entire somatic cell lineage from the one-cell stage to the adult (Sulston and Horvitz, 1977; Deppe et al., 1978; Kimble and Hirsh, 1979; Suslton et al., personal communication). Its ease of culture makes it an organism of choice for studies of various aspects of anatomy and physiology, including muscle formation and function (Zengel and Epstein, 1980; Mackenzie and Epstein, 1980), cuticle formation (Cox et al, 1981), neuroanatomy (Ward et al, 1975; Ware et al, 1975; Sulston et al, 1975), and behavior (Dusenbery, 1980). Several genes have been cloned by recombinant DNA techniques ablation (Kimble, 1981; Laufer and von Ehrenstin, 1981) procedures, as well as most of the modern molecular techniques, are in use.
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[
Trends in Ecology & Evolution,
1998]
Sexual reproduction is perhaps the greatest of all evolutionary puzzles. It's a puzzle because sexually reproducing species pay the cost of spending half their resources (over and above what is needed for vegetative growth) in producing males, whereas parthogenetic species utilize all their resources meant for reproduction in producing only females (or hermaphrodites) like themselves. This twofold cost of sexual reproduction is sometimes referred to as the twofold cost of producing males. Three advantages of sexual reproduction that might offset this cost have been proposed. Genetic recombination and cross fertilization permit sexually reproducing species to (1) bring together, in the same individual, mutations arising in different individuals; (2) generate genetic variability and thus adapt to changing environments; and (3) shuffle their genes in every generation and thus keep parasites at bay. While evolutionary biologists are busy testing their favourite ideas for offsetting the twofold cost of producing males, recent work by Craig LaMunyon and Samuel Ward shows that a nematode, Caenorhabditis briggsae, appears to have found a way of gaining the benefits of sexual reproduction without paying the cost of producing males.
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[
Proc Natl Acad Sci U S A,
1999]
Caenorhabditis elegans should soon be the first multicellular organism whose complete genomic sequence has been determined. This achievement provides a unique opportunity for a comprehensive assessment of the signal transduction molecules required for the existence of a multicellular animal. Although the worm C. elegans may not much resemble humans, the molecules that regulate signal transduction in these two organisms prove to be quite similar. We focus here on the content and diversity of protein kinases present in worms, together with an assessment of other classes of proteins that regulate protein phosphorylation. By systematic analysis of the 19,099 predicted C. elegans proteins, and thorough analysis of the finished and unfinished genomic sequences, we have identified 411 full length protein kinases and 21 partial kinase fragments. We also describe 82 additional proteins that are predicted to be structurally similar to conventional protein kinases even though they share minimal primary sequence identity. Finally, the richness of phosphorylation-dependent signaling pathways in worms is further supported with the identification of 185 protein phosphatases and 128 phosphoprotein-binding domains (SH2, PTB, STYX, SBF, 14-3-3, FHA, and WW) in the worm genome.