Dual localized kinesin‐12 POK 2 plays multiple roles during cell division and interacts with MAP 65‐3

Abstract

Kinesins are versatile nano-machines that utilize variable non-motor domains to tune specific motor microtubule encounters. During plant cytokinesis, the kinesin-12 orthologs, PHRAGMOPLAST ORIENTING KINESIN (POK)1 and POK2, are essential for rapid centrifugal expansion of the cytokinetic apparatus, the phragmoplast, toward a pre-selected cell plate fusion site at the cell cortex. Here, we report on the spatio-temporal localization pattern of POK2, mediated by distinct protein domains. Functional dissection of POK2 domains revealed the association of POK2 with the site of the future cell division plane and with the phragmoplast during cytokinesis. Accumulation of POK2 at the phragmoplast midzone depends on its functional POK2 motor domain and is fine-tuned by its carboxy-terminal region that also directs POK2 to the division site. Furthermore, POK2 likely stabilizes the phragmoplast midzone via interaction with the conserved microtubule-associated protein MAP65-3/PLEIADE, a well-established microtubule cross-linker. Collectively, our results suggest that dual localized POK2 plays multiple roles during plant cell division.

Plant Kinesin-12: Localization Heterogeneity and Functional Implications

“…PAKRP1/Kin12A and PAKRP1L/Kin12B belong to class II and regulate the organization of the phragmoplast during male sporogenesis [26,27,28]. The class I proteins POK1/Kin12C and POK2/Kin12D mediate accurate cell plate positioning (Figure 1) [6,7,8,12]. Although Kin12E (encoded by At3g44050 , class I, Figure 1) and Kin12F (encoded by At3g20150 , class II, Figure 1) have not yet been characterized, transcript profiling revealed that both are upregulated during mitosis, suggesting a cell division-related role [29].…”

“…During phragmoplast expansion towards the cell cortex, microtubules polymerize at its leading edge and depolymerize from the central lagging zone upon vesicle fusion and cell plate biosynthesis (Figure 3) [32]. Arabidopsis PAKRP1/Kin12A and PAKRP1L/Kin12B as well as POK2/Kin12D emerge during late anaphase and label the midzone of the phragmoplast until its disassembly at the end of cytokinesis (Figure 2 and Figure 3) [7,27]. Immunolocalization experiments also show OsKINESIN12A at the phragmoplast midzone in rice [22], supporting the notion that the association with the midzone might be a common feature of kinesin-12; although this requires further investigation.…”

“…A recently characterized candidate that might counterbalance the loss of PAKRP1/Kin12A and PAKRP1L/Kin12B function in somatic cells of the respective double mutants is kinesin POK2/Kin12D. It begins to accumulate at the phragmoplast midzone during the transition to cytokinesis and continuously localizes there until the disappearance of the phragmoplast (Figure 2) [7]. In a motility depended manner, POK2/Kin12D reaches the midzone where it interacts with MAP65-3 and likely some of its isoforms (Figure 3) [7].…”

“…It begins to accumulate at the phragmoplast midzone during the transition to cytokinesis and continuously localizes there until the disappearance of the phragmoplast (Figure 2) [7]. In a motility depended manner, POK2/Kin12D reaches the midzone where it interacts with MAP65-3 and likely some of its isoforms (Figure 3) [7]. The interaction with MAP65-3 is probably confining POK2/Kin12D at the midzone as it is diminished in ple-2 mutants [7].…”

“…In general, kinesin-12 members are characterized by the presence of an N-terminal motor domain, a neck β-sheet, and by the homology of the amino acid sequence in their C-terminal, which is abundant in coiled-coil domains (Figure 1) [5]. Plant kinesin-12 PHRAGMOPLAST ORIENTING KINESINS (POKs) are among the largest kinesins that have been reported so far [6,7,8]. Unlike their animal orthologs, upstream of the motor domain, plant kinesin-12 members possess an extraordinarily long N-terminal disordered region (Figure 1), which facilitates binding to various partners with high specificity [9].…”