Abstract
Both endogenous plant proteins and viral movement proteins associate with microtubules to promote their movement through plasmodesmata. The association of viral movement proteins with microtubules facilitates the formation of virus-associated replication complexes, which are required for the amplification and subsequent spread of the virus. However, the role of microtubules in the intercellular movement of plant proteins is less clear. Here we show that the SHORT-ROOT (SHR) protein, which moves between cells in the root to regulate root radial patterning, interacts with a type-14 kinesin, KINESIN G (KinG). KinG is a calponin homology domain kinesin that directly interacts with the SHR-binding protein SIEL (SHR-INTERACING EMBRYONIC LETHAL) and localizes to both microtubules and actin. Since SIEL and SHR associate with endosomes, we suggest that KinG serves as a linker between SIEL, SHR, and the plant cytoskeleton. Loss of KinG function results in a decrease in the intercellular movement of SHR and an increase in the sensitivity of SHR movement to treatment with oryzalin. Examination of SHR and KinG localization and dynamics in live cells suggests that KinG is a nonmotile kinesin that promotes the pausing of SHR-associated endosomes. We suggest a model in which interaction of KinG with SHR allows for the formation of stable movement complexes that facilitate the cell-to-cell transport of SHR.
Highlights
Both endogenous plant proteins and viral movement proteins associate with microtubules to promote their movement through plasmodesmata
Since SHR INTERACTING EMBRYONIC LETHAL (SIEL) and SHR associate with endosomes, we suggest that KINESIN G (KinG) serves as a linker between SIEL, SHR, and the plant cytoskeleton
We report the interaction between SHR and a type 14 kinesin-like motor protein, KINESIN G (KinG; At1g63640), which directly binds to an essential protein, SHR INTERACTING EMBRYONIC LETHAL (SIEL), and supports the cell-to-cell movement of SHR
Summary
Both endogenous plant proteins and viral movement proteins associate with microtubules to promote their movement through plasmodesmata. Cell-to-cell movement of transcription factors is a common form of intercellular communication in plants (Lucas et al, 1995; Kurata et al, 2005; Pi et al, 2015; Gallagher et al, 2014) Many of these mobile transcription factors function as positional signals that regulate various aspects of plant development, including embryonic development (Schlereth et al, 2010), shoot apical meristem maintenance (Lucas et al, 1995; Kim et al, 2005; Yadav et al, 2011), floral initiation (Sessions et al, 2000; Wu et al, 2003), root hair formation (Kurata et al, 2005; Savage et al, 2008), stomata differentiation (Raissig et al, 2017), and root patterning (Nakajima et al, 2001; Pi et al, 2015). Structurefunction analysis of SHR has shown that the movement of SHR via plasmodesmata is both targeted and
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