A rice class-XIV kinesin enters the nucleus in response to cold

Xiaolu Xu,Wilhelm J Walter,Isabel Machens,Qiong Liu,Peter Nick

doi:10.1038/s41598-018-21816-w

Xiaolu Xu, Wilhelm J Walter + Show 3 more

Open Access

https://doi.org/10.1038/s41598-018-21816-w

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Abstract

Higher plants possess a large number of kinesins, but lack the minus-end directed dynein motors. However, the kinesin class XIV has strongly expanded, and minus-end directed motors from this class may have taken over functions of cytoplasmic dyneins. In this study, we address the functional aspects of a novel rice homologue of the Arabidopsis class-XIV kinesins ATK1 and ATK5. Since a loss-of-function rice mutant of this kinesin is not viable, the function was studied in tobacco BY-2 as heterologous system. OsDLK-GFP stably expressed in BY-2 cells decorates cortical microtubules, but also can shift into the nucleus of interphase cells. Because of this peculiar localisation, we coined the name Dual Localisation Kinesin (DLK). The nuclear import of this protein is strongly and reversibly promoted in response to cold. During mitosis, OsDLK is repartitioned between spindle and phragmoplast. Motility assays in vitro using show that OsDLK can convey mutual sliding of microtubules and moves at a velocity comparable to other class-XIV kinesins. When tobacco cells overexpressing OsDLK are synchronised, they exhibit a delayed entry into metaphase, while the later phases of mitosis are accelerated. The data are discussed in relation to additional functions of this kinesin type, beyond their transport along microtubules.

Highlights

Higher plants possess a large number of kinesins, but lack the minus-end directed dynein motors
A 14-amino-acid neck-linker region directly upstream of the catalytic core comprises the consensus neck motif found among kinesins that move towards the minus end of microtubules[27]
We found that OsDLK-red fluorescent protein (RFP) decorated the green fluorescent protein (GFP)-labelled cortical microtubules (Fig. 4a–c), whereas the nucleus of the same cells harboured the RFP signal indicative of OsDLK, but no microtubular signal (Fig. 4d–f)

Summary

Introduction

Higher plants possess a large number of kinesins, but lack the minus-end directed dynein motors. Since the functionality of the division spindle requires microtubular transport in both directions, the functions conveyed by dyneins in animal cells must be taken over by minus-end directed kinesins in plants. Cortical microtubules (cMTs), the exclusive microtubule array in non-cycling plant cells, participate in the organisation of the cell wall[14] It is this function, which led to the discovery of microtubules by Ledbetter and Porter[15], and from the early days was proposed to be linked with transport along www.nature.com/scientificreports/. Several kinesins are shared between phragmoplast and cortical array, including several class-XIV kinesins, such as ATK57, or KCH11 This shared localisation might indicate that the machinery used to organise the new cell plate in dividing cells later has been recruited to organise the cell wall in expanding cells. ATK5 accumulates at the plus ends of growing cMTs, the atk[5] mutant shows a normal organisation of cMT7

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