Microtubules polarize in the direction of nuclear migration. (A and B) Images representing 3.9 s of EBP-1::GFP time-lapse sequences. The first 1.3 s are colored red, the next 1.3 s are colored green, and the last 1.3 s are colored blue to show directionality. Cell borders are outlined in white. Anterior is to the left. (A) Cells early in intercalation. (B) Cells with migrating nuclei. The nucleus in the left-most cell is migrating up, and direction alternates in every cell to the posterior. (A’ and B’) Cartoon representing direction of microtubule growth based on data in A and B. Nuclei and cell boundaries are outlined in white. (C and D) Quantification of the direction of microtubule growth by visualization of EBP-1::GFP comets early in intercalation (C) and during nuclear migration (D) for wild-type and klc-2(km11). Bars, 10 µm.