Figure 8. Cell death of the B_AG is delayed in rk⁴ mutants.

(A) Apoptosis is initiated within six hours of eclosion in the B_AG of Canton S control animals (CS, left) but not in those of rickets⁴ mutants (rk⁴, right). Each image is a composite of five merged confocal z-sections showing most of the B_AG (green) from a representative animal, visualized by anti-burs immunostaining. TUNEL labeling (magenta), which indicates DNA fragmentation, can be seen in the nuclei of all 11 B_AG from the control animal (left), but only one of 12 B_AG nuclei (arrow) is labeled in the nervous system preparation from a rk⁴ animal (right). TUNEL-labeled nuclei of many neurons other than the B_AG are also visible, consistent with a broader pattern of post-eclosion apoptosis (see Results).

(B) Volume rendered confocal micrographs of the abdominal ganglion and abdominal nerves (AN, arrowheads) from Canton S control (CS, left) and rickets⁴ (rk⁴, right) animals immunostained with anti-burs antibody. All B_AG are present in the abdominal ganglion of the rk⁴ mutant, while only two survive in the abdominal ganglion of the control animal (arrows). Substantial bursicon immunoreactivity is associated with the processes of surviving B_AG in the abdominal nerves of the rk⁴ mutants.

(C) Bar graph showing the percentage of B_AG neurons still present in animals at the indicated times after eclosion. CS, Canton S control animals; rk⁴, rickets mutants. Cell counts were averaged from at least six preparations for each genotype and time point.