Microtubule-associated proteins in higher plants.

A variety of microtubule-associated proteins (MAPs) have been reported in higher plants. Microtubule (MT) polymerization starts from the gamma-tubulin complex (gammaTuC), a component of the MT nucleation site. MAP200/MOR1 and katanin regulate the length of the MT by promoting the dynamic instability of MTs and cutting MTs, respectively. In construction of different MT structures, MTs are bundled or are associated with other components--actin filaments, the plasma membrane, and organelles. The MAP65 family and some of kinesin family are important in bundling MTs. MT plus-end-tracking proteins (+TIPs) including end-binding protein 1 (EB1), Arabidopsis thaliana kinesin 5 (ATK5), and SPIRAL 1 (SPR1) localize to the plus end of MTs. It has been suggested that +TIPs are involved in binding of MT to other structures. Phospholipase D (PLD) is a possible candidate responsible for binding of MTs to the plasma membrane. Many candidates have been reported as actin-binding MAPs, for example calponin-homology domain (KCH) family kinesin, kinesin-like calmodulin-binding protein (KCBP), and MAP190. RNA distribution and translation depends on MT structures, and several RNA-related MAPs have been reported. This article gives an overview of predicted roles of these MAPs in higher plants.