Flagellar Length Control

Chlamydomonas and other flagellated and ciliated organisms have evolved a specific and sophisticated mechanism for regulating flagellar length. The rate of regeneration of the growing flagellum is somehow coupled to the length of the resorbing flagellum. The strongest evidence that cells actively control flagellar length comes from experiments utilizing mutants with long flagella. Four genes, LF1, LF2, LF3 and LF4, have been identified in which mutation can lead to a long-flagella phenotype. Each of the genes has been cloned, and the gene product characterized. This is evidenced in this chapter with the mechanism of flagella length control. The LF1, LF2, and LF3 genes encode proteins (AAP83163, ABK34487, and AAO62545, respectively) that interact in the regulation of flagellar length. Although there may only be four genes that can produce a long-flagella phenotype upon mutagenesis, there are clearly many other genes involved in flagellar length control. Early models and balance point models are explained elaborately. Biochemical approaches to flagellar length control are likely to be the most important avenue for discovering additional proteins involved in the process.