Meckelin guides orientation of basal bodies along the striated rootlet

Abstract

Objective Meckelin (MKS3) functions in ciliogenesis and ciliary gating. MKS3 appears to have similar functions in Paramecium tetraurelia, i.e. FLAG-MKS3 is found associated slightly above each basal body and RNAi for MKS3 leads to loss of cilia. RNAi for MKS3 also leads to the disorganization of rows of basal bodies that run from anterior to posterior. In areas of misalignments, basal bodies with their post ciliary and transverse rootlets are found out of their expected rows. However, the rootlets are attached to the basal bodies at the expected angles relative to each other. We propose that MKS3 guides new basal bodies as they move toward the anterior of the cell along the striated rootlet (SR) of the parent basal body. Basal bodies without MKS3 lose their interactions with the parent’s SR. Without this guide to maintain orientation, new basal bodies migrate off the expected line and, when they form their SRs, these too cannot project toward the anterior as expected.