Plant kinesins: a bottom-up approach - from single molecules to function

During land colonisation, plants evolved new microtubule structures that have no functional analogues in opisthokonts, namely animals and fungi. The appearance of these unique structures, such as cortical microtubule arrays, the preprophase band, and the phragmoplast, coincided with the family expansion of kinesin motors. While most plant kinesins are classified into the same families as their opisthokont orthologues, many plant kinesins have not only increased functional redundancy but acquired additional or completely new functionality in various cellular processes. Although many opisthokont kinesins have been scrutinised down to the mechanics of a single motor, much less is known about the molecular details of plant kinesins. Insights from opisthokont kinesins are often used to infer how their corresponding plant kinesin counterparts might work in vivo with little molecular verification. In this review, we summarise current advances in in vitro characterisation of plant kinesins and highlight examples of how A. thaliana kinesins have diverged functionally. These examples illustrate that insights from opisthokont kinesins cannot be easily transferred to plant kinesins. Furthermore, they motivate the in vitro characterisation of each individual plant kinesin, a challenge we hope to overcome by promoting the use of reconstituted plant-kinesin assays.