Flexible Sex and Suspended Animation in Nematodes

There are two Caenorhabditis elegans sexes--male and self-fertilizing hermaphrodite--and males generally represent about 0.1% of a population. Sex is generally determined at fertilization by the ratio of X chromosomes to autosomes. Prahlad et al. now show that sex determination in cross-fertilized C. elegans is plastic and that sexual development can be altered after the embryo stage by exogenous factors. This ability to switch sexual phenotype and karyotype might allow the worm to optimize its development for the environmental conditions encountered. In another example of physiological flexibility, C. elegans can endure adverse environmental conditions by entering into an extreme, but temporary, state of quiescence called suspended animation. Nystul et al. report that for C. elegans to survive through this state in response to severe oxygen deprivation, two components of the mitotic spindle checkpoint pathway are required. In the absence of either of these factors, cells proceeded through metaphase but exhibited chromosomal missegregation. By engaging this mechanism of cell cycle arrest, the organisms ensure genome stability and survival until environmental conditions improve. V. Prahlad, D. Pilgrim, E. B. Goodwin, Roles for mating and environment in C. elegans sex determination. Science 302, 1046-1049 (2003). [Abstract] [Full Text] T. G. Nystul, J. P. Goldmark, P. A. Padilla, M. B. Roth, Suspended animation in C. elegans requires the spindle checkpoint. Science 302, 1038-1041 (2003). [Abstract] [Full Text]