Germline-specific role for unconventional components of the γ-tubulin complex in Caenorhabditis elegans

The {gamma}-tubulin complex ({gamma}TuC) is a widely conserved microtubule nucleator, but some of its components GCP4-6. Here, we identified two {gamma}TuC-associated proteins in C. elegans, namely GTAP-1 and -2, for which apparent orthologs were detected only in the genus Caenorhabditis. Their centrosomal localization was interdependent. In early C. elegans embryos, whereas the conserved {gamma}TuC component MZT-1/MOZART1 was essential for the localization of centrosomal {gamma}-tubulin, depletion of GTAP-1 and/or -2 caused up to 50% reduction of centrosomal {gamma}-tubulin and precocious disassembly of spindle poles during mitotic telophase. In the adult germline, GTAP-1 and GTP-2 contributed to the efficient recruitment of {gamma}TuC to the plasma membrane. Depletion of GTAP-1, but not GTAP-2, severely disrupted both the microtubule array and the honeycomb-like structure in the adult germline. We propose that GTAP-1 and -2 are unconventional components of {gamma}TuC that contribute to the organization of both centrosomal and non-centrosomal microtubules by targeting the {gamma}TuC to specific subcellular sites in a tissue-specific manner. SUMMARY STATEMENTHaruta et al. show that GTAP-1 and -2, two unconventional components of the {gamma}-tubulin complex ({gamma}TuC) in C. elegans, contribute to targeting the {gamma}TuC to embryonic centrosomes and germ-cell membrane in adults.