scholarly journals AtCRK5 Protein Kinase Exhibits a Regulatory Role in Hypocotyl Hook Development during Skotomorphogenesis

2019 ◽  
Vol 20 (14) ◽  
pp. 3432 ◽  
Author(s):  
Abu Imran Baba ◽  
Norbert Andrási ◽  
Ildikó Valkai ◽  
Teréz Gorcsa ◽  
Lilla Koczka ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Protein Kinase ◽  
Auxin Transport ◽  
Polar Auxin Transport ◽  
Fine Tuning ◽  
Regulatory Role ◽  
Protein Activity ◽  
Directional Movement ◽  
Pat Proteins

Seedling establishment following germination requires the fine tuning of plant hormone levels including that of auxin. Directional movement of auxin has a central role in the associated processes, among others, in hypocotyl hook development. Regulated auxin transport is ensured by several transporters (PINs, AUX1, ABCB) and their tight cooperation. Here we describe the regulatory role of the Arabidopsis thaliana CRK5 protein kinase during hypocotyl hook formation/opening influencing auxin transport and the auxin-ethylene-GA hormonal crosstalk. It was found that the Atcrk5-1 mutant exhibits an impaired hypocotyl hook establishment phenotype resulting only in limited bending in the dark. The Atcrk5-1 mutant proved to be deficient in the maintenance of local auxin accumulation at the concave side of the hypocotyl hook as demonstrated by decreased fluorescence of the auxin sensor DR5::GFP. Abundance of the polar auxin transport (PAT) proteins PIN3, PIN7, and AUX1 were also decreased in the Atcrk5-1 hypocotyl hook. The AtCRK5 protein kinase was reported to regulate PIN2 protein activity by phosphorylation during the root gravitropic response. Here it is shown that AtCRK5 can also phosphorylate in vitro the hydrophilic loops of PIN3. We propose that AtCRK5 may regulate hypocotyl hook formation in Arabidopsis thaliana through the phosphorylation of polar auxin transport (PAT) proteins, the fine tuning of auxin transport, and consequently the coordination of auxin-ethylene-GA levels.

scholarly journals CRK5 Protein Kinase Contributes to the Progression of Embryogenesis of Arabidopsis thaliana

2019 ◽  
Vol 20 (24) ◽  
pp. 6120 ◽  
Author(s):  
Baba ◽  
Valkai ◽  
Labhane ◽  
Koczka ◽  
Andrási ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Protein Kinase ◽  
Embryo Development ◽  
Auxin Transport ◽  
Polar Auxin Transport ◽  
Fine Tuning ◽  
Calcium Dependent ◽  
Directional Movement ◽  
Pat Proteins

The fine tuning of hormone (e.g., auxin and gibberellin) levels and hormone signaling is required for maintaining normal embryogenesis. Embryo polarity, for example, is ensured by the directional movement of auxin that is controlled by various types of auxin transporters. Here, we present pieces of evidence for the auxin-gibberellic acid (GA) hormonal crosstalk during embryo development and the regulatory role of the Arabidopsis thaliana Calcium-Dependent Protein Kinase-Related Kinase 5 (AtCRK5) in this regard. It is pointed out that the embryogenesis of the Atcrk5-1 mutant is delayed in comparison to the wild type. This delay is accompanied with a decrease in the levels of GA and auxin, as well as the abundance of the polar auxin transport (PAT) proteins PIN1, PIN4, and PIN7 in the mutant embryos. We have previously showed that AtCRK5 can regulate the PIN2 and PIN3 proteins either directly by phosphorylation or indirectly affecting the GA level during the root gravitropic and hypocotyl hook bending responses. In this manuscript, we provide evidence that the AtCRK5 protein kinase can in vitro phosphorylate the hydrophilic loops of additional PIN proteins that are important for embryogenesis. We propose that AtCRK5 can govern embryo development in Arabidopsis through the fine tuning of auxin-GA level and the accumulation of certain polar auxin transport proteins.

scholarly journals The PINOID protein kinase regulates organ development in Arabidopsis by enhancing polar auxin transport

Development ◽  
2001 ◽  
Vol 128 (20) ◽  
pp. 4057-4067 ◽  
Author(s):  
René Benjamins ◽  
Ab Quint ◽  
Dolf Weijers ◽  
Paul Hooykaas ◽  
Remko Offringa
Keyword(s):  
Protein Kinase ◽  
Auxin Transport ◽  
Vascular Tissue ◽  
Primary Root ◽  
Ectopic Expression ◽  
Polar Auxin Transport ◽  
Fine Tuning ◽  
35S Promoter ◽  
Serine Threonine Kinase ◽  
Transport Inhibitors

Arabidopsis pinoid mutants show a strong phenotypic resemblance to the pin-formed mutant that is disrupted in polar auxin transport. The PINOID gene was recently cloned and found to encode a protein-serine/threonine kinase. Here we show that the PINOID gene is inducible by auxin and that the protein kinase is present in the primordia of cotyledons, leaves and floral organs and in vascular tissue in developing organs or proximal to meristems. Overexpression of PINOID under the control of the constitutive CaMV 35S promoter (35S::PID) resulted in phenotypes also observed in mutants with altered sensitivity to or transport of auxin. A remarkable characteristic of high expressing 35S::PID seedlings was a frequent collapse of the primary root meristem. This event triggered lateral root formation, a process that was initially inhibited in these seedlings. Both meristem organisation and growth of the primary root were rescued when seedlings were grown in the presence of polar auxin transport inhibitors, such as naphthylphtalamic acid (NPA). Moreover, ectopic expression of PINOID cDNA under control of the epidermis-specific LTP1 promoter provided further evidence for the NPA-sensitive action of PINOID. The results presented here indicate that PINOID functions as a positive regulator of polar auxin transport. We propose that PINOID is involved in the fine-tuning of polar auxin transport during organ formation in response to local auxin concentrations.

AtPIP5K1, an Arabidopsis thaliana phosphatidylinositol phosphate kinase, synthesizes PtdIns(3,4)P2 and PtdIns(4,5)P2 in vitro and is inhibited by phosphorylation

2001 ◽  
Vol 359 (3) ◽  
pp. 583-589 ◽  
Author(s):  
Tomas WESTERGREN ◽  
Stephen K. DOVE ◽  
Marianne SOMMARIN ◽  
Christophe PICAL
Keyword(s):  
Arabidopsis Thaliana ◽  
Alkaline Phosphatase ◽  
Protein Kinase ◽  
Protein Kinase A ◽  
Substrate Specificities ◽  
Phosphatidylinositol Phosphate ◽  
Dual Substrate Specificity ◽  
Kinase A ◽  
Dual Substrate

PtdIns phosphate kinases (PIPkins), which generate PtdInsP2 isomers, have been classified into three subfamilies that differ in their substrate specificities. We demonstrate here that the previously identified AtPIP5K1 gene from Arabidopsis thaliana encodes a PIPkin with dual substrate specificity in vitro, capable of phosphorylating PtdIns3P and PtdIns4P to PtdIns(3,4)P2 and PtdIns(4,5)P2 respectively. We also show that recombinant AtPIP5K1 is phosphorylated by protein kinase A and a soluble protein kinase from A. thaliana. Phosphorylation of AtPIP5K1 by protein kinase A is accompanied by a 40% inhibition of its catalytic activity. Full activity is recovered by treating phosphorylated AtPIP5K1 with alkaline phosphatase.

scholarly journals Characterization of the Rac-GAP (Rac-GTPase-activating protein) activity of β2-chimaerin, a ‘non-protein kinase C’ phorbol ester receptor

2003 ◽  
Vol 375 (2) ◽  
pp. 313-321 ◽  
Author(s):  
Maria Jose CALOCA ◽  
HongBin WANG ◽  
Marcelo G. KAZANIETZ
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Gtpase Activating Protein ◽  
Protein Activity ◽  
Rac Gtpase ◽  
Kinase C ◽  
Phorbol Ester Receptor

The regulation and function of β2-chimaerin, a novel receptor for the phorbol ester tumour promoters and the second messenger DAG (diacylglycerol), is largely unknown. As with PKC (protein kinase C) isoenzymes, phorbol esters bind to β2-chimaerin with high affinity and promote its subcellular distribution. β2-Chimaerin has GAP (GTPase-activating protein) activity for the small GTP-binding protein Rac1, but for not Cdc42 or RhoA. We show that acidic phospholipids enhanced its catalytic activity markedly in vitro, but the phorbol ester PMA had no effect. β2-Chimaerin and other chimaerin isoforms decreased cellular levels of Rac-GTP markedly in COS-1 cells and impaired GTP loading on to Rac upon EGF (epidermal growth factor) receptor stimulation. Deletional and mutagenesis analysis determined that the β2-chimaerin GAP domain is essential for this effect. Interestingly, PMA has a dual effect on Rac-GTP levels in COS-1 cells. PMA increased Rac-GTP levels in the absence of a PKC inhibitor, whereas under conditions in which PKC activity is inhibited, PMA markedly decreased Rac-GTP levels and potentiated the effect of β2-chimaerin. Chimaerin isoforms co-localize at the plasma membrane with active Rac, and these results were substantiated by co-immunoprecipitation assays. In summary, the novel phorbol ester receptor β2-chimaerin regulates the activity of the Rac GTPase through its GAP domain, leading to Rac inactivation. These results strongly emphasize the high complexity of DAG signalling due to the activation of PKC-independent pathways, and cast doubts regarding the selectivity of phorbol esters and DAG analogues as selective PKC activators.

scholarly journals The Arabidopsis thaliana AGRAVITROPIC 1 gene encodes a component of the polar-auxin-transport efflux carrier

1998 ◽  
Vol 95 (25) ◽  
pp. 15112-15117 ◽  
Author(s):  
R. Chen ◽  
P. Hilson ◽  
J. Sedbrook ◽  
E. Rosen ◽  
T. Caspar ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Auxin Transport ◽  
Polar Auxin Transport

scholarly journals Fine-tuning of ABA responses by the protein kinase WNK8

2018 ◽  
Author(s):  
Rainer Waadt ◽  
Kenji Hashimoto ◽  
Esther Jawurek ◽  
Melanie Krebs ◽  
Martin Scholz ◽  
...  
Keyword(s):  
Abscisic Acid ◽  
Protein Kinase ◽  
Signaling Pathway ◽  
Direct Interaction ◽  
Negative Regulator ◽  
Fine Tuning ◽  
Dependent Manner ◽  
In Planta ◽  
Young Seedling

SUMMARYThe phytohormone abscisic acid (ABA) regulates various growth- and developmental processes in response to limiting water conditions. ABA functions through an established signaling pathway consisting of PYR1/PYL/RCAR ABA receptors that inhibit group A type 2C protein phosphatases (PP2Cs) in an ABA-dependent manner. Inhibition of PP2Cs enables the activation of SnRK2-type protein kinases that phosphorylate downstream targets including transcription factors and ion channels. However, ABA-dependent signals have to be integrated into other growth- and developmental programs to ensure a successful life cycle. Here, we have characterized the role of the protein kinase WNK8 in the ABA signalling pathway. Two T-DNA insertion alleles wnk8-1 and wnk8-4 exhibited contrasting ABA responses during seed germination and young seedling growth. However, reciprocal crossings with wild type plants suggested that wnk8-1 that still expressed the WNK8 kinase domain functioned in a hypermorphic and dominant manner. WNK8 directly interacted with the PP2C PP2CA in planta and was negatively regulated by this phosphatase in vitro. WNK8 also phosphorylated the ABA receptor PYR1 in vitro. Double mutant analyses revealed that the dominant allele wnk8-1 suppressed the ABA- and glucose hypersensitivity of the pp2ca-1 T-DNA allele. In transient protoplast assays WNK8 suppressed ABA-induced reporter gene expression that was dependent on a functional kinase. In summary, we have identified the protein kinase WNK8 as a negative regulator of ABA responses during young seedling establishment through its direct interaction with core ABA signaling components.SIGNIFICANCE STATEMENTThe phytohormone abscisic acid regulates the water household of plants through a defined core signaling pathway. Here we have identified the protein kinase WNK8 as a direct interactor of core abscisic acid signalling components and as a negative modulator of abscisic acid responses during young seedling development in Arabidopsis.

scholarly journals Coumarin Interferes with Polar Auxin Transport Altering Microtubule Cortical Array Organization in Arabidopsis thaliana (L.) Heynh. Root Apical Meristem

2021 ◽  
Vol 22 (14) ◽  
pp. 7305
Author(s):  
Leonardo Bruno ◽  
Emanuela Talarico ◽  
Luz Cabeiras-Freijanes ◽  
Maria Letizia Madeo ◽  
Antonella Muto ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Lateral Root ◽  
Apical Meristem ◽  
Root Formation ◽  
Auxin Transport ◽  
Primary Root ◽  
Polar Auxin Transport ◽  
Root Apical Meristem ◽  
Lateral Root Formation ◽  
Cortical Array

Coumarin is a phytotoxic natural compound able to affect plant growth and development. Previous studies have demonstrated that this molecule at low concentrations (100 µM) can reduce primary root growth and stimulate lateral root formation, suggesting an auxin-like activity. In the present study, we evaluated coumarin’s effects (used at lateral root-stimulating concentrations) on the root apical meristem and polar auxin transport to identify its potential mode of action through a confocal microscopy approach. To achieve this goal, we used several Arabidopsis thaliana GFP transgenic lines (for polar auxin transport evaluation), immunolabeling techniques (for imaging cortical microtubules), and GC-MS analysis (for auxin quantification). The results highlighted that coumarin induced cyclin B accumulation, which altered the microtubule cortical array organization and, consequently, the root apical meristem architecture. Such alterations reduced the basipetal transport of auxin to the apical root apical meristem, inducing its accumulation in the maturation zone and stimulating lateral root formation.

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