The katana was a long sword carried by samurai in feudal Japan. In modern biology, it has a namesake: katanin, a protein named for its function, severing cellular microtubules from their formation sites.
One of the largest collections of katana is held in Nagoya, so it was appropriate that a group of scientists from the Nagoya University Institute of Transformative Bio-molecules (WPI-ITbM), cooperating with researchers from the Nara Institute of Science and Technology, made a significant discovery regarding the recruiting of katanin in the formation and organization of cortical microtubules in plant cells, which was published in Nature Communications on June 17th 2021.
Microtubules are polymers of tubulin which form part of the cytoskeleton, and are involved in a number of essential cellular processes, with their orientation affecting chromosome segregation, cell polarity and cell morphogenesis. It is understood that both the formation and severing of microtubules is key to their organization. In particular, the selective and efficient severing of microtubules at their formation site by the protein katanin, so that these newly-formed daughter microtubules can move to the cortex of the cell and stimulate interaction with other microtubules, is important. However, the molecular mechanism that recruits the katanin severing factor to the site at which the microtubules form has long remained unknown.
The researchers, whose team at NU was led by ITbM Co-PI Designated Lecturer Masayoshi Nakamura, found that the Msd1-Wdr8 'anchor molecule' complex, which stabilizes the microtubules at the nucleation sites, controls the accumulation of katanin at the microtubule formation sites to enable the efficient release of daughter microtubules. Thus, the recruitment of severing factors performed by Msd1-Wdr8 and their effects on microtubule stability may seem incompatible, but this strict regulation likely increases plants' ability to precisely control their microtubule severing processes.
Katanin severs microtubules at specific sites in animal and plant cells, which leads to active reorganization of the microtubule organization. This study will inform future research on whether the Msd1-Wdr8 complex in animal cells also recruits katanin, and whether other sites use similar mechanisms for the stabilization and release of daughter microtubules. The results of this study will be of interest to cell biologists not only in plants but also other organisms.
Journal: Nature Communications
Title: An anchoring complex recruits katanin for microtubule severing at the plant cortical nucleation sites
Authors: Noriyoshi Yagi, Takehide Kato, Sachihiro Matsunaga, David W. Ehrhardt, Masayoshi Nakamura, Takashi Hashimoto
Find out more about the Institute of Transformative Bio-molecules (ITbM)