The Caspase-Related Protease Separase (EXTRA SPINDLE POLES) Regulates Cell Polarity and Cytokinesis inArabidopsis   

Abstract

Vesicle trafficking plays an important role in cell division, establishment of cell polarity, and translation of environmental cues to developmental responses. However, the molecular mechanisms regulating vesicle trafficking remain poorly understood. Here, we report that the evolutionarily conserved caspase-related protease separase (EXTRA SPINDLE POLES [ESP]) is required for the establishment of cell polarity and cytokinesis in Arabidopsis thaliana. At the cellular level, separase colocalizes with microtubules and RabA2a (for RAS GENES FROM RAT BRAINA2a) GTPase-positive structures. Separase facilitates polar targeting of the auxin efflux carrier PIN-FORMED2 (PIN2) to the rootward side of the root cortex cells. Plants with the radially swollen4 (rsw4) allele with compromised separase activity, in addition to mitotic failure, display isotropic cell growth, perturbation of auxin gradient formation, slower gravitropic response in roots, and cytokinetic failure. Measurements of the dynamics of vesicle markers on the cell plate revealed an overall reduction of the delivery rates of KNOLLE and RabA2a GTPase in separase-deficient roots. Furthermore, dissociation of the clathrin light chain, a protein that plays major role in the formation of coated vesicles, was slower in rsw4 than in the control. Our results demonstrate that separase is a key regulator of vesicle trafficking, which is indispensable for cytokinesis and the establishment of cell polarity.

Peroxisomal polyamine oxidase and NADPH-oxidase cross-talk for ROS homeostasis which affects respiration rate in Arabidopsis thaliana

“…On the other hand, in Arabidopsis there are ten genes encoding DAOs, four of which have been characterized. One of them is an apoplastic enzyme; however, six remain to be characterized (Moschou et al, 2013; Planas-Portell et al, 2013). These suggest that most likely the contribution of the apoplast to the Spd-dependent production of ${\mathrm{O}}_{\mathrm{2}}^{\mathrm{•}\mathrm{-}}$ is rather minimal in Arabidopsis .…”

Tudor Staphylococcal Nuclease Links Formation of Stress Granules and Processing Bodies with mRNA Catabolism in Arabidopsis

“…The assay was performed as described previously (Moschou et al, 2013). Five-day-old seedlings were grown on sterile CellView cell culture plates with glass bottoms (35 mm; Greiner Bio One) containing 1 mL of half-strength MS, 1% (w/v) sucrose, and 0.3% (w/v) electrophoresis-grade agarose.…”

Polar Auxin Transport Is Essential for Medial versus Lateral Tissue Specification and Vascular-Mediated Valve Outgrowth in Arabidopsis Gynoecia

“…For analysis of PIN localization, the inflorescences were fixed for 1 h in a solution containing 3.7% (v/v) paraformaldehyde, 50 mM PIPES, pH 6.8, 5 mM EGTA, 2 mM MgSO 4 , and 0.4% (w/v) Triton X-100 (modified from Moschou et al, 2013). Fixation kept the GFP signal stable for up to 24 h. After washing with phosphate-buffered saline, floral meristems and gynoecia were individually harvested and mounted in water.…”