Signals fly when kinases meet Rho-of-plants (ROP) small G-proteins

Fehér, Attila; Lajkó, Dézi Bianka

doi:10.1016/j.plantsci.2015.05.007

Cited by 31 publications

(29 citation statements)

References 106 publications

(198 reference statements)

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The Arabidopsis genome contains a single ortholog of the mammalian DOC180 family protein, SPIKE1 (SPK1; Qiu et al, 2002), and 14 plant-specific RopGEF family members with the PRONE (plant-specific Rop nucleotide exchanger) domain required for GTP–GDP exchange (Berken et al, 2005; Gu et al, 2006). Several ROP downstream effectors—a family of CRIB-domain-containing proteins (RICs) that specifically interact with active GTP-bound ROPs—have been described in plants (Nagawa et al, 2010; Fehér and Lajkó, 2015). Although RICs are highly variable, their CRIB motifs are highly conserved (Nagawa et al, 2010), and the CRIB motif is used widely to estimate active ROP levels using a pull-down assay with a ROP-interactive CRIB motif-containing protein 1 (Ric1) that specifically targets activated forms of RAC/ROPs (Tao et al, 2002).…”

Section: Auxin Perception and Signalingmentioning

confidence: 99%

Auxin Signaling in Regulation of Plant Translation Reinitiation

Schepetilnikov

Ryabova

2017

Front. Plant Sci.

View full text Add to dashboard Cite

The mRNA translation machinery directs protein production, and thus cell growth, according to prevailing cellular and environmental conditions. The target of rapamycin (TOR) signaling pathway—a major growth-related pathway—plays a pivotal role in optimizing protein synthesis in mammals, while its deregulation triggers uncontrolled cell proliferation and the development of severe diseases. In plants, several signaling pathways sensitive to environmental changes, hormones, and pathogens have been implicated in post-transcriptional control, and thus far phytohormones have attracted most attention as TOR upstream regulators in plants. Recent data have suggested that the coordinated actions of the phytohormone auxin, Rho-like small GTPases (ROPs) from plants, and TOR signaling contribute to translation regulation of mRNAs that harbor upstream open reading frames (uORFs) within their 5′-untranslated regions (5′-UTRs). This review will summarize recent advances in translational regulation of a specific set of uORF-containing mRNAs that encode regulatory proteins—transcription factors, protein kinases and other cellular controllers—and how their control can impact plant growth and development.

show abstract

Section: Auxin Perception and Signalingmentioning

confidence: 99%

Auxin Signaling in Regulation of Plant Translation Reinitiation

Schepetilnikov

Ryabova

2017

Front. Plant Sci.

View full text Add to dashboard Cite

show abstract

“…Similar to phosphorylation effects on Rho proteins, ROP protein phosphorylation may influence their activity by altering GTP‐binding by ROP, by altering ROP subcellular localization, or by affecting ROP protein interactions (Figure ). Multiple kinase families have been implicated in phosphorylation of ROP proteins or ROP protein regulators, including AGC‐type kinases, calcium‐dependent protein kinases, MAP kinases, receptor‐like kinases, and other membrane‐bound kinases (for review, see Fehér and Lajkó, ). In this study, we identified MKK3 • MPK1 • RBK1 as a potential kinase cascade that terminates in ROP protein phosphorylation.…”

Section: Discussionmentioning

confidence: 99%

“…Because mutants defective in MKK3 , MPK1 , and RBK1 , display hypersensitivity to the effects of auxin (Figures , and ), and mutants defective in ROP4 or ROP6 display resistance to auxin (Robert et al ., ; Xu et al ., ; Chen et al ., ), we hypothesize the RBK1‐mediated phosphorylation may act to negatively influence ROP4 and ROP6 activity (Figure ). Further, additional kinases, including AGC kinases, calcium‐dependent protein kinases, MAP kinases, receptor‐like kinases, and other membrane‐bound kinases, likely also act to modulate ROP activity, either through phosphorylation of ROPs or by phosphorylation of ROP regulators (Figure ; for review, see Fehér and Lajkó, ). Additional in planta experiments will allow researchers to tease apart roles for each of these kinases on ROP activity.…”

Section: Discussionmentioning

confidence: 99%

“…In human cells, Rho phosphorylation increases interactions with GUANINE NUCLEOTIDE DISSOCIATION INHIBI-TORS (GDIs), and thus alters Rho subcellular localization, inhibits GTP-binding activity, and increases protein stability (for review, see Loirand et al, 2006). Likewise, phosphorylation has been proposed as a regulator of plant ROP activity, either by direct phosphorylation of ROP proteins or by indirect phosphorylation of the ROP regulators, such as GTPASE ACTIVATING PROTEINS (GAPs), GUANINE EXCHANGE FACTORS (GEFs), and GUANINE NUCLEOTIDE DISSOCIATION INHIBITORS (GDIs) (for review, see Feh er and Lajk o, 2015). Similar to phosphorylation effects on Rho proteins, ROP protein phosphorylation may influence their activity by altering GTP-binding by ROP, by altering ROP subcellular localization, or by affecting ROP protein interactions (Figure 7).…”

Section: Rop Proteins Influence Actin Cytoskeleton Polymerization Andmentioning

confidence: 99%

See 1 more Smart Citation

An Arabidopsis kinase cascade influences auxin‐responsive cell expansion

2017

View full text Add to dashboard Cite

SUMMARY Mitogen-activated protein kinase (MPK) cascades are conserved mechanisms of signal transduction across eukaryotes. Despite the importance of MPK proteins in signaling events, specific roles for many Arabidopsis MPK proteins remain unknown. Multiple studies have suggested roles for MPK signaling in a variety of auxin-related processes. To identify MPK proteins with roles in auxin response, we screened mpk insertional alleles and identified mpk1-1 as a mutant that displays hypersensitivity in auxin-responsive cell expansion assays. Further, mutants defective in the upstream MAP kinase kinase MKK3 also display hypersensitivity in auxin-responsive cell expansion assays, suggesting that this MPK cascade affects auxin-influenced cell expansion. We further found that MPK1 interacts with and phosphorylates ROP BINDING PROTEIN KINASE 1 (RBK1), a protein kinase that interacts with members of the Rho-like GTPases from Plants (ROP) small GTPase family. Similar to mpk1-1 and mkk3-1 mutants, rbk1 insertional mutants display auxin hypersensitivity, consistent with a possible role for RBK1 downstream of MPK1 in influencing auxin-responsive cell expansion. We found that RBK1 directly phosphorylates ROP4 and ROP6, consistent with the possibility that RBK1 effects on auxin-responsive cell expansion are mediated through phosphorylation-dependent modulation of ROP activity. Our data suggest a MKK3 • MPK1 • RBK1 phosphorylation cascade that may provide a dynamic module for altering cell expansion.

show abstract

“…Auxin-sensing ROP GTPases are conserved molecular switches that function in many signal transduction events (Fehér and Lajkó, 2015). Studies of the mechanism of TOR activation by ROP2 led to the discovery that ROP2 physically binds TOR and promotes its activation, if bound to GTP (Schepetilnikov et al, 2017).…”

Section: Upstream Control Of Translation Via Tor Hormone Signaling Tomentioning

confidence: 99%

Recent Discoveries on the Role of TOR (Target of Rapamycin) Signaling in Translation in Plants

2017

View full text Add to dashboard Cite

Protein synthesis is an intricate, energy-demanding, and tightly controlled process that plays a fundamental role in cell growth, proliferation, and differentiation. The target of rapamycin (TOR) protein kinase integrates stress-, nutrient-, and energy-related signals to optimize protein synthesis outputs. In mammals, TOR is a main controller of capped mRNA translation; how TOR participates in translation initiation in plants is unclear, but active TOR is required for regulation of translation of mRNA with 59-untranslated region (59-UTR) upstream open reading frames (uORFs)-known translation regulatory elements in eukaryotes. Recent data implicates diverse signals such as stress, hormones, and metabolites in regulation of TOR signal transduction pathways and, thus, in response to environmental stress. Here, we review current knowledge of plant TOR complex composition and activation, and its function in translation, compiling data on downstream processes that are under stringent control of TOR in mammals but not yet investigated in plants.Plants have evolved various adaptation mechanisms to ensure their optimal growth, with plant development and behavior being strongly responsive to various external and internal stimuli. By monitoring their environment, plants trigger signal transduction cascades in order to regulate downstream cellular processes, mainly via protein synthesis-a major energy-consuming process (Buttgereit and Brand, 1995). The TOR protein kinase integrates extracellular signals (hormones, biotic and abiotic stresses, growth factors) together with intracellular nutrient availability and energy status to control protein synthesis and other anabolic processes if conditions are favorable, and represses catabolic processes such as autophagy (Albert and Hall, 2015). The past 10 years has boosted research on plant TOR complex composition, highlighted TOR upstream signals and downstream targets, and revealed an interplay between TOR signaling and hormonal, stress, and other pathways in photosynthetic organisms. We are beginning to understand how TOR is activated, and how it controls many cellular processes, such as transcription, translation, and autophagy. Here, we give an overview of recent results on the role of TOR in plant translation control and draw the reader's attention to future questions to address. In plants, inactivation of TOR correlates with a decrease in total polysomal levels (Deprost et al., 2007;Schepetilnikov et al., 2011Schepetilnikov et al., , 2013, strongly suggesting a role for TOR in plant translation. Although a role for TOR in global translation in plants has been documented, the players and mechanisms used to influence different steps of translation initiation -the step most controlled by TOR in mammals-are only starting to emerge. Here, we summarize the current state of knowledge of specific plant translation initiation mechanisms that are controlled by 59-UTR elements of mRNAs and discuss regulation of these mechanisms by TOR/S6 kinase 1 (S6K1) signaling. Examples where TOR re...

show abstract

Signals fly when kinases meet Rho-of-plants (ROP) small G-proteins

Cited by 31 publications

References 106 publications

Auxin Signaling in Regulation of Plant Translation Reinitiation

Auxin Signaling in Regulation of Plant Translation Reinitiation

An Arabidopsis kinase cascade influences auxin‐responsive cell expansion

Recent Discoveries on the Role of TOR (Target of Rapamycin) Signaling in Translation in Plants

Contact Info

Product

Resources

About