In Trypanosoma brucei a single flagellum originates at the posterior part of the cell and remains attached to the cell body throughout most of its length. For this attachment, the flagellar attachment zone (FAZ), which consists of a microtubule quartet and a FAZ filament, is crucial. However, only few factors involved in the assembly and maintenance of the flagellum have been characterised thus far. Ziyin Li and colleagues (p. ) now used localisation-based screening to identify FAZ2 as a new FAZ filament protein that is required for flagellum adhesion. They found that FAZ2 knockdown (KD) disrupted cytokinesis and destabilised FAZ filament proteins and, by conducting 2D difference gel electrophoresis together with mass spectrometry, identified eight new flagellum-associated proteins that are affected by FAZ2 KD. The authors then analysed the immunoprecipitates of FAZ2 using liquid-chromatography tandem mass spectrometry and found the first FAZ filament complex described thus far, which is formed between FAZ2, CC2D and KMP11. Finally, the authors were also able to show that the FAZ filament is formed at the region proximal to the flagellum base, whereas the flagellum is assembled from the distal tip side. This study, while conducted independently, is in accordance with the recent J. Cell. Sci. publication by , which also identified FAZ2, and showed that the FAZ and flagellum assemble in opposite directions. Taken together, these independent studies, thus, provide important new insights into different aspects of flagellar morphogenesis.
