The ?-tubulin complex protein GCP6 is crucial for spindle morphogenesis but not essential for microtubule reorganization in Arabidopsis.

ABSTRACT: ?-Tubulin typically forms a ring-shaped complex with 5 related ?-tubulin complex proteins (GCP2 to GCP6), and this ?-tubulin ring complex (?TuRC) serves as a template for microtubule (MT) nucleation in plants and animals. While the ?TuRC takes part in MT nucleation in most eukaryotes, in fungi such events take place robustly with just the ?-tubulin small complex (?TuSC) assembled by ?-tubulin plus GCP2 and GCP3. To explore whether the ?TuRC is the sole functional ?-tubulin complex in plants, we generated 2 mutants of the GCP6 gene encoding the largest subunit of the ?TuRC in Arabidopsis thaliana Both mutants showed similar phenotypes of dwarfed vegetative growth and reduced fertility. The gcp6 mutant assembled the ?TuSC, while the wild-type cells had GCP6 join other GCPs to produce the ?TuRC. Although the gcp6 cells had greatly diminished ?-tubulin localization on spindle MTs, the protein was still detected there. The gcp6 cells formed spindles that lacked MT convergence and discernable poles; however, they managed to cope with the challenge of MT disorganization and were able to complete mitosis and cytokinesis. Our results reveal that the ?TuRC is not the only functional form of the ?-tubulin complex for MT nucleation in plant cells, and that ?-tubulin-dependent, but ?TuRC-independent, mechanisms meet the basal need of MT nucleation. Moreover, we show that the ?TuRC function is more critical for the assembly of spindle MT array than for the phragmoplast. Thus, our findings provide insight into acentrosomal MT nucleation and organization.

SUBMITTER: Miao H 

PROVIDER: S-EPMC6936555 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature