Microtubule-organizing centres in plants

The organization of microtubules into ordered arrays is essential for cell division and differentiation. Centrosomes have long been recognized as major components of this process in metazoans, Most plant cells, however, do not have such morphologically distinct organelles, although they do have functionally equivalent microtubule-organizing centres, Recent discoveries have shed new light on these mysterious organelles. A key element is gamma-tubulin, which is ubiquitous in eukaryotes, including plants, Multiprotein complexes with gamma-tubulin -'gamma-somes' - probaby serve as templates for microtubule initiation. Microtubules can also self-organize into ordered arrays in the presence of motor proteins, providing evidence that the organization of microtubule arrays involves both nucleation and polymer translocation. These exciting findings pave the way for elucidating the identity of the diffuse microtubule-organizing centres in plants and the principles of microtubule organization without centrosomes.