Chemotaxis during development when cells become polarized. (A) Chemotaxis to 1 μM cAMP in the absence of PI3K and PLA2 activity (inhibited with LY and BPB or removed by disruption of the encoding genes). Cells without PI3K and PLA2 activity exhibit poor chemotaxis at 5 h of development but very strong chemotaxis at 7 h of development. The chemotactic response of cells that do have PI3K and/or PLA2 activity (WT, pi3k null, and pla2 null) is indicated by the horizontal gray bar. The data presented are the means and SEM of at least three independent measurements. (B) Morphology of 5- and 7-h starved cells expressing myosin-II–RFP and LimEΔcoil-GFP detecting actin filaments. Bar, 10 μm.