A gene essential for viability and flagellar regeneration maps to the uni linkage group of Chlamydomonas reinhardtii

We have isolated a mutant of Chlamydomonas reinhardtii that is both temperature sensitive for viability and temperature sensitive for flagellar regeneration. The mutation (designated tnr1, for temperature-sensitive nonregenerator) has been genetically mapped to a position near uni1 on the uni linkage group (ULG), an unusual genetically circular linkage group consisting primarily of mutations affecting flagellar assembly or function. tnr1 is the first essential gene identified on this linkage group, and is one of the few essential genes affecting flagellar function identified to date. We also find that tnr1 cells are not defective for induction of new tubulin transcripts or protein synthesis during flagellar regeneration at the nonpermissive temperature, and that at least a portion of the unassembled pool of flagellar proteins in mutant cells is assembly-competent at the nonpermissive temperature.