Endomembrane asymmetry can be reoriented. Zygotes were grown in unilateral light until 6 h AF (L1), at which time the light direction was reversed (L2). Zygotes were labeled for 30 min at hourly intervals beginning at 6 h AF and scored as having polar adhesive or endomembrane in accordance with L1 or L2. Zygotes with uniform labeling were not scored. (a) Adhesive deposited in accordance with L1 (arrow) was not resorbed and a second zone of polar adhesive (arrowhead) was deposited in accordance with L2. Bar = 50 μm. (b) Adhesive deposition reversed following light reversal. Note that filled squares represent adhesive localization with L1 and open circles represent zygotes with two patches of polar adhesive. (c) Endomembrane localization with L1 (filled squares) decreased with time after light reversal and localization with L2 (open circles) increased. Over 100 zygotes were scored for each time point and the experiment was repeated three times. Bars are standard errors.