Figure 4. Migration of bnl-LexA expressing cells in embryonic development. A-J.

morphogenetic movement of dorsolateral bnl-clusters and corresponding dorsal branch (green) in each body segment; live time lapse images taken once every 10-min duration. A, 3D projections of time lapse images at 0 (stage 12), 50, 100,150 and 200 min of a growing embryo; intimate interactions and migrations of both dorso-lateral bnl-clusters (red) and dorsal branch (green) were detected; epithelial edge in dorsal closure is marked by dashed line; #1-2, two body segments; downward arrows (white), leading edges of dorsal clusters in #1 and #2; upward white arrows, trailing ends of the lateral clusters in #1 and #2; green arrows, tips of the dorsal branches in #1 and #2; converging tracks of dorsal bnl-clusters over the amnioserosa were visible at 200 min; induction of bnl expression in amnioserosa was visible from 50 min onwards; a gradual increase in bnl transcription in dorsolateral clusters was detected from 0-150 min; see corresponding Supplementary Movie-1. A′ tracked migration routes (from 0-150′) of the -leading ends of dorsal bnl-clusters, -trailing ends of the lateral bnl-clusters, and the corresponding tracheal tips in #1 and #2 segments of the embryo shown in (A). B, B′; coordinated growth kinetics of the leading edge of the dorsal bnl-cluster (red), trailing end of the lateral bnl- cluster (purple dash line) and corresponding tip of dorsal branch (green) in #1 (B) and #2 (B′) body segments of the embryo shown in (A); see corresponding Supplementary Movies 4, 9. C, tracked migration routes of six cells constituting a dorsal cluster in 3D space from 40 min (stage 12) to 130 min of imaging; panels showing images at every 30 min duration; M_s, center of mass (white x) of the group at the origin; M_e, center of mass (red +) of the same group at the end of experiment; dashed arrow shows the displacement of the center of mass of the dorsal cluster in 2D; see corresponding movies 3,5,7. D-J, showing a lateral bnl-cluster from a posterior segment of an embryo (D) containing six cells and their relative position in the cluster at various time point (E-J); see corresponding supplementary movies 2, 6; J, migration tracks of the six cells in lateral cluster from 30 to 280 min of recording (see Supplementary movie 8); white dashed arrow, the displacement of center of mass in 2D. K, rose plots showing directed migration of each of the six cell in a dorsal cluster (left) and in a lateral cluster (right) over time from posterior segments of two different embryos that are similarly oriented while imaging; plots show a coherent dorsal-ward migration. L-N, patterns of cellular contacts between the tracheal tip cells and the bnl source marked by syb-GFP reconstitution at different embryonic developmental stages; bnl-expressing cells expressed nsyb-GFP^1-10 and trachea expressed CD4:GFP¹¹ and CD8:RFP (btl-Gal4; bnl-LexA X lexO-nsybGFP^1-10, UAS-CD4:GFP¹¹; UAS-CD8:RFP); All embryo panels, anterior - left, dorsal - up. A-J, time durations are relative to the 0 min (start of imaging, normally stage 11-12); genotype: A-J, btl-Gal4, UAS-CD8:GFP; bnl-LexA, lexO-mCherryCAAX. Scale bars, 30μm.