A dual role for cell plate‐associated PI4Kβ in endocytosis and phragmoplast dynamics during plant somatic cytokinesis

Abstract

Plant cytokinesis involves membrane trafficking and cytoskeletal rearrangements. Here, we report that the phosphoinositide kinases PI4Kβ1 and PI4Kβ2 integrate these processes in Arabidopsis thaliana (Arabidopsis) roots. Cytokinetic defects of an Arabidopsis pi4kβ1 pi4kβ2 double mutant are accompanied by defects in membrane trafficking. Specifically, we show that trafficking of the proteins KNOLLE and PIN2 at the cell plate, clathrin recruitment, and endocytosis is impaired in pi4kβ1 pi4kβ2 double mutants, accompanied by unfused vesicles at the nascent cell plate and around cell wall stubs. Interestingly, pi4kβ1 pi4kβ2 plants also display ectopic overstabilization of phragmoplast microtubules, which guide membrane trafficking at the cell plate. The overstabilization of phragmoplasts in the double mutant coincides with mislocalization of the microtubule‐associated protein 65‐3 (MAP65‐3), which cross‐links microtubules and is a downstream target for inhibition by the MAP kinase MPK4. Based on similar cytokinetic defects of the pi4kβ1 pi4kβ2 and mpk4‐2 mutants and genetic and physical interaction of PI4Kβ1 and MPK4, we propose that PI4Kβ and MPK4 influence localization and activity of MAP65‐3, respectively, acting synergistically to control phragmoplast dynamics.

“Salicylic Acid Mutant Collection” as a Tool to Explore the Role of Salicylic Acid in Regulation of Plant Growth under a Changing Environment

“…A clear example is the comparison of bon1-1 phenotype (small rosette and almost WT-size roots) to pi4kβ1β2, which also had small rosettes but impaired root growth (Figures 1 and 3). Our data confirmed the critical role of PI4Kβ1β2 for root growth (Figure 3) [16,25]. To precisely analyse the SA role in seedlings' sensitivity to light, we used the subset of WT, sid2, pi4kβ1β2 and sid2pi4kβ1β2.…”

“…Particular interest has been devoted to mutants with altered phospholipid turnover/signalling and vesicular trafficking that were reported to have pleiotropic effects, often connected with SA accumulation. In particular, pi4kβ1β2 mutation in phosphatidylinositol-4-kinases β1 and β2 was recently reported as an SA overaccumulator [16,17], or exo70b1-1 [18]. fah1/fah2 is deficient in fatty acid hydroxylase genes and also showed enhanced immune responses and a modulated sphingolipid profile [19].…”

Phosphorylation of the exocyst subunit Exo70B2 contributes to the regulation of its function

“…the disruption of the Exo70/Sec3-phospholipid complex, is mediated. Arrival at the PM also implies spatial proximity to signalling complexes, including soluble kinases, which can be recruited by other proteins (Xie et al, 2014; Zhang et al, 2015; Lin et al, 2019). Spatial proximity may result in phosphorylation of Exo70B2, and thus, its release from the membrane (Figure 8).…”

Identification of salicylic acid-independent responses in an Arabidopsis phosphatidylinositol 4-kinase beta double mutant

“…Callose biosynthesis and accumulation have been shown to be affected by vesicle trafficking (Ellinger and Voigt 2014). PI4Ks has been shown to play an important role in cytokinesis (Lin et al 2019), especially in the correct organization of the vesicles at the cell division plane and further formation of a cell plate. During phragmoplast formation, PI4Kβ1 likely interacts with MPK4, a member of the MAP65 protein family that regulates microtubule organization (Lin et al, 2019).…”

“…PI4Ks has been shown to play an important role in cytokinesis (Lin et al 2019), especially in the correct organization of the vesicles at the cell division plane and further formation of a cell plate. During phragmoplast formation, PI4Kβ1 likely interacts with MPK4, a member of the MAP65 protein family that regulates microtubule organization (Lin et al, 2019). Callose is also essential for cytokinesis (Thiele et al 2009).…”