Worm Breeder's Gazette 15(3): 19 (June 1, 1998)
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.
University of Wisconsin, 425 Henry Mall Rm. 5350, Madison, WI 53706
The redistribution of mitochondria in the period following fertilization through the first cell division was followed in the early embryos of two related nematodes, Caenorhabditis elegans and Acrobeloides sp. PS1146, using a combination of vital staining with a mitochondrial-specific dye Rhodamine 6G, and confocal laser-scanning microscopy. In C. elegans embryos mitochondria are part of the same bulk flow directed toward the sperm pronucleus that has been implicated in generating the initial A-P axis asymmetry (Strome, S. And Wood, W.B. Cell 35, 15-25 (1983); Hird, S.N. And White, J.G. J. Cell Biology 121, 1343 1355 (1993)). Concomitant with these flows, during the period of cytoplasmic rearrangement known as !pseudocleavage!, most of the cortical mitochondria are found only in the posterior, and following the first cell division the posterior blastomere P1 inherits roughly twenty per cent more mitochondria than its anterior sister AB. This redistribution does not require the presence of either an anterior actin cap or a pseudocleavage since the same pattern was observed in nop-1 mutant embryos in which these structures are missing. In contrast, in Acrobeloides sp. PS1146 embryos the sperm pronucleus does not direct any cytoplasmic rearrangements, and the P-granules are segregated differently. During pronuclear migration they do not become asymmetrically distributed. Most are on the surface of the pronuclei, and the rest are loosely distributed throughout the cytoplasm. During metaphase most of the P-granules are situated around the chromosomes, and by anaphase they redistribute primarily around one of the two microtubule asters (Goldstein, B. et al., Current Biology 8(5): 303. 1998 Feb 26). We found that during pronuclear migration the mitochondria are either around the pronuclei or distributed throughout the cytoplasm, and following the formation of the first spindle they are seen to translocate in radial paths toward the aster centers. This probably indicates transport along astral microtubules mediated by minus-end directed motors. Comparing the two species studied we find that the pattern of redistribution of mitochondria correlates closely with that of the P-granules.