Engulfment precedes the B.al/rapaav death. a All non-refractile B.al/rapaav cells are unengulfed, most cells that are round with partial cytoplasmic refractility are engulfed by P12.pa and all fully refractile cells are engulfed by P12.pa. Representative DIC and fluorescent images corresponding to each of the B.al/rapaav morphology classes are shown, with the P12.pa (dashed red line) and B.al/rapaav cell membranes (dashed blue line) outlined (based on P
::mCherry::PH signal). All animals were in the fourth larval stage, but were at slightly different ages for visualization of B.al/rapaav at different stages of the death process. b, c A B.arapaav cell with partial cytoplasmic refractility (white arrow) visualized by (b) DIC and (c) electron microscopy (blue arrowheads). c The B.arapaav cell is engulfed by P12.pa (red arrows) but otherwise does not display obvious ultrastructural signs of cell death. The animal was of genotype him-8.
d B.al/rapaav does not die in a weak engulfment mutant without being engulfed. Engulfment and cell-killing are not independent events (P = 0.0075, Fisher’s exact test). B.al/rapaav was classified as being dead or undead based on morphology as seen with DIC optics and was then examined to determine whether it was inside of P12.pa based on P
::mCherry::PH. Animals were of the genotype nIs343; ced-10 him-8; nIs735