Fig. 4. kal-1 mutants show altered male tails. (A-F) DIC photomicrographs; ventral views. Control tail (A): the nine rays on each side are indicated. (B-F) kal-1 mutants. White arrows indicate loss or strong reduction of rays; black arrows indicate abnormal shape, extra rays or fusion of rays. In D, combination of DIC and epifluorescence image of a kal-1(gb503) mutant worm, which is also transgenic for evIs82a [unc-129 ns::GFP; dpy-20(+)] (Colavita and Culotti, 1998). This transgene specifically expresses GFP in one of ray 5 sensory neurons (white arrowhead), allowing to establish that ray 5 maintains its identity, but is posterior to ray 6 (black arrowhead). (G) Schematic representation of the outline of epithelial cells at three different times during tail formation in wild-type L4 males [modified from Baird et al. (Baird et al., 1991)]. During early L4, the tail seam cells (indicated by stars), which are next to the clusters of ray precursors (numbered 1 to 9), are still separated from each other. At mid L4, tail seam cells have partially fused together to form the SET (seam tail) cell, which maintains its connection with the most posterior body seam cell and with the ray clusters. At late L4, the fusion of tail seam is complete and the flanking hyp7 cell has engulfed the ray clusters. The SET cell maintains its contact with body seam throughout the process. (H,I) Confocal images of developing male tails at the L4 stage stained with AbMH27: wild type in H; kal-1(gb503) in I. Numbers from 1 to 9 indicate the clusters of precursors of sensory rays. The typical triangular arrangement of precursors to rays 4, 5 and 6 of the control tail (H) is changed to an almost straight line in the mutant tail (white arrow in I). This arrangement of epithelial cells in L4 will result, in the adult tail, in the inversion between the position of ray 5 and 6 (D) or in their fusion. In I, the shape of the SET cell, which does not contact the posterior body seam cell, is also abnormal.
