Figure 5

The actin cytoskeleton is twisted and lengthened in twisted pharynges. (A-C) Pharyngeal actin was stained using phalloidin-FITC and one confocal section is shown for each of the indicated genotypes. Note that in all the specimens, the actin filaments are evenly spaced and generally aligned near-perpendicularly to the longitudinal axis of the pharynx if it were untwisted. In (B), note that strong degrees of twist can be detected in both the procorpus (leftmost portion) and at the isthmus between the two bulbs in the mutant pharynx, but only subtle twisting within each bulb. (D) and (E) show extracted optical cross sections from within the isthmus of the indicated genotype. The actin fibers are more twisted, hence longer, in the isthmus from mnm-4 specimen than in the N2 control. This is illustrated schematically in (F) which depicts the shapes of wild-type actin fibers in the left half, and of mnm-4 in the right half. The ratio of the average length of the actin fibers over the isthmus diameter was 0.42 ± 0.02 (s.e.m.) for N2, 0.54 ± 0.03 for mnm-4, 0.51 ± 0.04 for dig-1, 0.43 ± 0.04 for mig-4 and 0.43 ± 0.02 for unc-61; n ≥ 3 worms. Only mnm-4 significantly differed from N2 (t-test, P = 0.009).