pbl mutants have defects in furrow MT and central spindle organization. All panels show fixed embryos. green, α-tubulin and slight γ-tubulin; red, PH3 and Scribble (for all stains except R [green, Pbl; blue, α-tubulin]). (A–L) WT (A–F) and pbl² (G–L) from cycle 14 metaphase (A and G) through cycle 15 interphase (F and L). (A′–L′) Merged images correspond to A–L. (M) Percentage of normal (+++), weak (++), and severely disrupted (+) spindles at various stages in WT and pbl². Metaphase, n = 46 (WT) and 43 (pbl²); anaphase, n = 32 (WT) and 36 (pbl²); early telophase, n = 28 (WT) and 27(pbl²); late telophase, n = 27 (WT) and 24 (pbl²); and scission, n = 53 (WT) and 42 (pbl²). (N) Some Pbl-deficient cells form weak furrows that complete invagination (arrow) but fail to maintain the central spindle. (O and P) Magnification of equatorial region in WT (O and O′) and pbl² (P) cells. O′ and P were taken from C′ and I′, respectively. Furrow and MT structures are labeled in O. Arrowheads and brackets mark the cleavage plane and central spindle, respectively, in O′ and P. pbl² embryos lack furrow MTs and show a weak central spindle (P). (Q) Percentage of normal (+++), weak (++), and severely disrupted (+) furrow MTs during early telophase in WT and pbl². n = 41 (WT) and 33 (pbl²). (R) Pbl shows punctate localization where furrow MTs contact the leading furrow edge (arrows). Bars, 4 μm. Error = SEM among embryos.