Poc1 is required to resist ciliary forces and its WD40 domain is not in the A/C linker. (A) Inhibition of ciliary beating with NiCl2 rescues the poc1Δ BB loss phenotype at high force. This was also shown in Meehl et al. (2016). Cells were stained with anti-centrin antibody. Scale bar is 10 μm. (B) SIM images of Poc1 N-terminal tag (GFP) versus C-terminal tag (HaloTag). Rings are only seen with N-terminal tags. Scale bar is 100 nm. (C) Negative stain of isolated poc1Δ BBs demonstrating that some BBs maintained their overall structure (white arrowhead), whereas some were severely disintegrated (red arrowhead). Scale bar is 400 nm. (D) The doughnut-shaped density previously proposed to be Poc1 in the A/C linker of Chlamydomonas BBs is also present in wild-type Tetrahymena BBs and remains present in poc1Δ Tetrahymena BBs. Proximal end TMTs from Chlamydomonas (left, blue), wild-type Tetrahymena (middle, gray), and poc1Δ Tetrahymena BBs (right, green) in cross section (top) and exterior side views (bottom). Arrowheads point to the location of the density previously proposed to be Poc1 (Li et al., 2019).
