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In the ciliate Tetrahymena thermophila, the BCD1 pattern-gene encodes a Beige-BEACH-domain protein that defines cortical organelle dimensions through regulated endocytic activity. Tetrahymena cells homozygous for a bcd1 loss-of-function mutation exhibit supernumerary cortical organelles including oral apparatuses, cytoprocts and contractile vacuole pores. Elements of the broadened cortical domain phenotype can be phenocopied by disrupting clathrin-mediated endocytosis, suggesting that exocytic membrane delivery is balanced by endocytic retrieval of cortical pattern determinants.. 

Motile cilia beat with an asymmetric waveform consisting of a power stroke that generates a propulsive force and a recovery stroke that returns the cilium back to the start. Cilia are anchored to the cell cortex by basal bodies (BBs) that are directly coupled to the ciliary doublet microtubules (MTs). We find that, consistent with ciliary forces imposing on BBs, bending patterns in BB triplet MTs are responsive to ciliary beating. BB bending varies as environmental conditions change the ciliary waveform. Bending occurs where striated fibers (SFs) attach to BBs and mutants with short SFs that fail to connect to adjacent BBs exhibit abnormal BB bending, supporting a model in which SFs couple ciliary forces between BBs. Finally, loss of the BB stability protein Poc1, which helps interconnect BB triplet MTs, prevents the normal distributed BB and ciliary bending patterns. Collectively, BBs experience ciliary forces and manage mechanical coupling of these forces to their surrounding cellular architecture for normal ciliary beating.