Function of the Arabidopsis kinesin-4, FRA1, requires abundant processive motility
Processivity is important for kinesins that mediate intracellular transport. Structure-function analyses of N-terminal kinesins have identified several non-motor regions that affect processivity in vitro. However, whether these structural elements affect kinesin processivity and function in vivo is not known. Here, we used an Arabidopsis kinesin-4, called Fragile Fiber1 (FRA1), which is thought to mediate vesicle transport to test whether mutations that alter processivity in vitro behave similarly in vivo and whether processivity is important for FRAs function. We generated several FRA1 mutants that differed in their run lengths in vitro and then transformed them into the fra1-5 mutant for complementation and in vivo motility analyses. Our data show that the behavior of processivity mutants in vivo can differ dramatically from in vitro properties, underscoring the need to extend structure-function analyses of kinesins in vivo. In addition, we found that high density of processive motility is necessary for FRA1s physiological function.\n\nSummaryThis study shows that the motility of kinesin mutants can differ significantly between in vitro and in vivo conditions and that abundant processive motility is important for FRA1 kinesins function.