Involvement of YODA and mitogen activated protein kinase 6 in Arabidopsis post‐embryogenic root development through auxin up‐regulation and cell division plane orientation

Abstract

Summary The role of YODA MITOGEN ACTIVATED PROTEIN KINASE KINASE KINASE 4 (MAPKKK4) upstream of MITOGEN ACTIVATED PROTEIN KINASE 6 (MPK6) was studied during post-embryonic root development of Arabidopsis thaliana. Loss- and gain-of-function mutants of YODA (yda1 and ΔNyda1) were characterized in terms of root patterning, endogenous auxin content and global proteomes.We surveyed morphological and cellular phenotypes of yda1 and ΔNyda1 mutants suggesting possible involvement of auxin. Endogenous indole-3-acetic acid (IAA) levels were up-regulated in both mutants. Proteomic analysis revealed up-regulation of auxin biosynthetic enzymes tryptophan synthase and nitrilases in these mutants. The expression, abundance and phosphorylation of MPK3, MPK6 and MICROTUBULE ASSOCIATED PROTEIN 65–1 (MAP65-1) were characterized by quantitative polymerase chain reaction (PCR) and western blot analyses and interactions between MAP65-1, microtubules and MPK6 were resolved by quantitative co-localization studies and co-immunoprecipitations.yda1 and ΔNyda1 mutants showed disoriented cell divisions in primary and lateral roots, abortive cytokinesis, and differential subcellular localization of MPK6 and MAP65-1. They also showed deregulated expression of TANGLED1 (TAN1), PHRAGMOPLAST ORIENTING KINESIN 1 (POK1), and GAMMA TUBULIN COMPLEX PROTEIN 4 (GCP4).The findings that MPK6 localized to preprophase bands (PPBs) and phragmoplasts while the mpk6-4 mutant transformed with MPK6AEF (alanine (A)–glutamic acid (E)–phenylanine (F)) showed a root phenotype similar to that of yda1 demonstrated that MPK6 is an important player downstream of YODA. These data indicate that YODA and MPK6 are involved in post-embryonic root development through an auxin-dependent mechanism regulating cell division and mitotic microtubule (PPB and phragmoplast) organization.

Biotechnological aspects of cytoskeletal regulation in plants

“…One notable example is the identification of a microtubule minus-end directed calmodulin-binding kinesin in A. thaliana (Reddy et al, 1996a,b) which is conserved in monocots and dicots but does not seem to have orthologues in mammals, yeast, fruit fly, Caenorhabditis elegans or red algae (Abdel-Ghany et al, 2005). Two other unique plant kinesins were identified in rice, one of which simultaneously binds to microtubules and actin microfilaments via calponin homology domain (O. sativa Kinesin with Calponin Homology1; OsKCH1; Frey et al, 2009Frey et al, , 2010 having orthologues in tobacco (NtKCH; Klotz and Nick, 2012) and cotton (GhKCH1 and GhKCH2; Preuss et al, 2004;Xu et al, 2009) (Smékalová et al, 2014). A. Cortical microtubules of post-mitotic root epidermal cells, exhibiting various organization patterns.…”

“…A cell similar to that depicted in (a) but with cortical microtubules arranged parallel to each other and transversely oriented with respect to the cell axis. Such cells exhibit longitudinal growth as exemplified by elongating root epidermal cells of A. thaliana (Smékalová et al, 2014). C. A cell entering growth phase with randomly arranged cortical microtubules will undergo isotropic growth resulting in cell bulging.…”

“…More importantly, studies showed that the microtubule binding activity of MAP65-1 is negatively regulated by reversible phosphorylation by CMGC kinases (cyclin-dependent kinases (CDKs), MAPKs, glycogen synthase kinases (GSKs) and CDK-like kinases). Among them, especially CDKs and MAPKs (Beck et al, 2010;Smékalová et al, 2014;Smertenko et al, 2006) provide an inducible switch of specific MAP65-1 interaction with the microtubule surface throughout the plant cell cycle (Komis et al, 2011;Sasabe and Machida, 2012).…”

Advances in Imaging Plant Cell Dynamics

“…Thus, Ove cka et al (2015) showed live coimaging of actin filaments and microtubules in the cotyledon epidermal cells, while von Wangenheim et al (2016) tracked cell fate by simultaneous imaging of plasma membrane and nuclear markers during lateral root formation. LSFM, unlike other live cell-imaging techniques, was able to successfully localize signaling protein such as mitogenactivated protein kinase 6 (MPK6) to the preprophase band of Arabidopsis root meristematic cells (Smékalová et al, 2014). One possible target of MPK6 is plantspecific EB1c.…”

AIK1, A Mitogen-Activated Protein Kinase, Modulates Abscisic Acid Responses through the MKK5-MPK6 Kinase Cascade

“…The main reason for this may be the multifunctional nature of MPK6, which plays essential roles in plant stress responses, growth, and development (Nakagami et al, 2005;Xing et al, 2008Xing et al, , 2009Schikora et al, 2011;Dutilleul et al, 2012;Xu and Zhang, 2015). Actually, MPK6 is a common target among several MAPK cascades Meng et al, 2012;Smékalová et al, 2014). Another possibility is the mutants of AIK1 and MKK5 used for phenotype analysis are the knockdown mutants (the aik1 knockout mutant probably is lethal).…”