A minus-end-directed kinesin with plus-end tracking protein activity is involved in spindle morphogenesis.
Diverse kinesin motor proteins are involved in spindle function; however, the mechanisms by which they are targeted to specific sites within spindles are not well understood. Here, we show that a fusion between yellow fluorescent protein (YFP) and a minus-end-directed Kinesin-14 (C-terminal family) from Arabidopsis, ATK5, localizes to mitotic spindle midzones and regions rich in growing plus-ends within phragmoplasts. Notably, in Arabidopsis interphase cells, YFP::ATK5 localizes to microtubules with a preferential enrichment at growing plus-ends; indicating ATK5 is a plus-end tracking protein (+TIP). This +TIP activity is conferred by regions outside of the C-terminal motor domain, which reveals the presence of independent plus-end tracking and minus-end motor activities within ATK5. Furthermore, mitotic spindles of atk5 null mutant plants are abnormally broadened. Based on these data, we propose a model in which ATK5 uses plus-end tracking to reach spindle midzones, where it then organizes microtubules via minus-end-directed motor activity.
Ambrose
J Christian
JC
Department of Biology, The Pennsylvania State University, University Park, 16802, USA.
Li
Wuxing
W
Marcus
Adam
A
Ma
Hong
H
Cyr
Richard
R
D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism*; D016547:Kinesins / Q000737:chemistry / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D008941:Spindle Apparatus / Q000737:chemistry / Q000378:metabolism*
D029681:Arabidopsis Proteins; C502922:ATK5 protein, Arabidopsis; D016547:Kinesins