Arabidopsis GCP2 and GCP3 are part of a soluble [gamma]-tubulin complex and have nuclear envelope targeting domains

• Published in: The Plant journal : for cell and molecular biology 2007-10, Vol.52 (2), p.322
• Main Authors: Seltzer, Virginie, Janski, Natacha, Canaday, Jean, Herzog, Etienne, Erhardt, Mathieu, Evrard, Jean-Luc, Schmit, Anne-Catherine
• Format: Article
• Language: English
• Subjects: Botany; Cellular biology; Molecular biology
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2007.03240.x

In higher plants, microtubules (MTs) are assembled in distinctive arrays in the absence of a defined organizing center. Three MT nucleation sites have been described: the nuclear surface, the cell cortex and cortical MT branch points. The Arabidopsis thaliana (At ) genome contains putative orthologues encoding all the components of characterized mammalian nucleation complexes: [gamma]-tubulin and [gamma]-tubulin complex proteins GCP2 to GCP6. We have cloned the cDNA encoding At GCP2, and show that [gamma]-tubulin, At GCP2 and At GCP3 are part of the same tandem affinity-purified complex and are present in a large membrane-associated complex. In addition, small soluble [gamma]-tubulin complexes of the size expected for a [gamma]-tubulin core complex are recruited to isolated nuclei. Using immunogold labelling, At GCP3 is localized to both the nuclear envelope (NE) and the plasma membrane. To identify domains that could play a role in targeting complexes to these nucleation sites, truncated At GCP2- and At GCP3-green fluorescent protein fusion proteins were expressed in BY-2 cells. Several domains from At GCP2 and At GCP3 are capable of targeting fusions to the NE. We propose that regulated recruitment of soluble [gamma]-tubulin-containing complexes is responsible for nucleation at dispersed sites in plant cells and contributes to the formation and organization of the various MT arrays. [PUBLICATION ABSTRACT]