CSAR1 RING domain is required for function. (A and B) Maximum intensity Z-projections of confocal stacks of CSAR1^MUT-3xHA (ERK7^AID) parasites grown for 24 h (A) without IAA and (B) with IAA to degrade ERK7^AID. Parasites were visualized with GFP-tubulin (blue), and antibodies against HA (green) and the apical cap marker ISP1 (red). Note that CSAR1^MUT signal concentrates with retained cytoskeleton (yellow stars) in the residual bodies of mature parasites (white arrowheads) regardless of whether ERK7 is present. Also note that CSAR1^MUT parasites retain their maternal conoids (orange arrowheads) after replication, even when ERK7 has been degraded. All scale bars are 10 μm.