ArabidopsisHomologs of Nucleus- and Phragmoplast-Localized Kinase 2 and 3 and Mitogen-Activated Protein Kinase 4 Are Essential for Microtubule Organization

Abstract

A double homozygous recessive mutant in the Arabidopsis thaliana homologs of nucleus-and phragmoplast-localized kinase 2 (ANP2) and 3 (ANP3) genes and a homozygous recessive mutant in the mitogen-activated protein kinase 4 (MPK4) gene of Arabidopsis exhibit deficiencies in the overall microtubule (MT) organization, which result in abnormal cell growth patterns, such as branching of root hairs and swelling of diffusely growing epidermal cells. Genetic, pharmacological, molecular, cytological, and biochemical analyses show that the major underlying mechanism for these phenotypes is excessive MT stabilization manifested in both mutants as heavy MT bundling, disorientation, and drug stability. The above defects in MAPK signaling result in the adverse regulation of members of the microtubule-associated protein (MAP65) protein family, including strongly diminished phosphorylation of MAP65-1. These data suggest that ANP2/ANP3, MPK4, and the microtubule-associated protein MAP65-1, a putative target of MPK4 signaling, are all essential for the proper organization of cortical microtubules in Arabidopsis epidermal cells.

The Arabidopsis NUCLEUS- AND PHRAGMOPLAST-LOCALIZED KINASE1-Related Protein Kinases Are Required for Elicitor-Induced Oxidative Burst and Immunity

“…In ANP mutants, cytokinetic defects and root defects are similar to those of loss-of-function mutants for MPK4, which, like NPK1, localizes to the phragmoplast and physically interacts with MAP65-1, a major microtubulecross-linking protein that regulates the stability and turnover of phragmoplast microtubules (Krysan et al, 2002;Beck et al, 2010Beck et al, , 2011. ANPs have been shown to functionally interact with proteins that are required for cytokinesis and thought to control stability and turnover of microtubules (Takahashi et al, 2010;Komis et al, 2011).…”

“…As in the case of MEKK1, lack of ANPs results in dwarfism, insensitivity to hydrogen peroxide (Nakagami et al, 2006), and basal up-regulation of RET-OX, CYP81F2, and FRK1 (this work). However, lack of ANPs and MPK4 result in cytokinesis and primary root developmental defects, which are both independent of MEKK2 (Beck et al, 2010). Thus, ANPs and MPK4, but not MEKK1, may functionally interact during plant growth and development .…”

“…Triple mutants were constructed by down-regulating, in an inducible manner, the expression of the third gene family member in both the double mutants anp1 anp2 and anp2 anp3. Only the latter double mutant exhibits developmental defects (Krysan et al, 2002;Beck et al, 2010Beck et al, , 2011. Conditional silencing was obtained by individually expressing ANP3-and ANP1-specific artificial microRNAs (amiRNAs), respectively, under the control of a b-estradiol-inducible promoter.…”

The Folylpolyglutamate Synthetase Plastidial Isoform Is Required for Postembryonic Root Development in Arabidopsis

“…Components of these signaling and developmental networks include a dynamic cytoskeleton and vesicular trafficking system, both of which play pivotal roles in regulating membrane recycling and cell wall deposition to sustain normal root growth (Bernal et al, 2008;Yoo et al, 2008;Beck et al, 2010). Also part of the intricate developmental networks that govern root growth are a collection of transcription factors and an array of chemical messengers, including sugars, nutrients, amino acids, and most of the major plant hormones (Benková and Hejátko, 2009;Forde and Walch-Liu, 2009;Iyer-Pascuzzi et al, 2009).…”

Advances in purification and separation of posttranslationally modified proteins

“…These tags preferentially capture phosphomonoester dianions bound to Ser, Thr and Tyr residues. The detection is based either on a mobility shift of phosphorylated proteins in SDS-PAGE (polyacrylamide-bound tags) or tag-reporter conjugates [61,69]. The fluorescent Phos-tag™ Phosphoprotein Gel Stain produced by Perkin Elmer (www.perkinelmer.com) exploited this technique, but it is no longer available.…”