SNF1-related Kinase Research Articles

SnRK1 Kinase and the NAC Transcription Factor SOG1 Are Components of a Novel Signaling Pathway Mediating the Low Energy Response Triggered by ATP Depletion.

Plant growth is strictly controlled by cell division, elongation, and differentiation for which adequate supplies of intracellular ATP are required. However, it is unclear how changes in the amount of intracellular ATP affect cell division and growth. To reveal the specific pathway dependent on ATP concentration, we performed analyses on the Arabidopsis mitochondria mutation sd3. The mutant is tiny, a result of a low amount of ATP caused by the disruption of Tim21, a subunit of the TIM23 protein complex localized in the inner membrane of the mitochondria. Loss of function of suppressor of gamma response 1 (SOG1) also restored the dwarf phenotype of wild type treated with antimycin A, a blocker of ATP synthesis in mitochondria. The sd3 phenotype is partially restored by the introduction of sog1, suppressor of gamma response 1, and kin10/kin11, subunits of Snf1-related kinase 1 (SnRK1). Additionally, SOG1 interacted with SnRK1, and was modified by phosphorylation in planta only after treatment with antimycin A. Transcripts of several negative regulators of the endocycle were up-regulated in the sd3 mutant, and this high expression was not observed in sd3sog1 and sd3kin11. We suggest that there is a novel regulatory mechanism for the control of plant cell cycle involving SnRK1 and SOG1, which is induced by low amounts of intracellular ATP, and controls plant development.

Overexpression of PpSnRK1α in Tomato Promotes Fruit Ripening by Enhancing RIPENING INHIBITOR Regulation Pathway.

As a conserved kinase complex, sucrose non-fermenting-1-related protein kinase 1 (SnRK1) is a major regulator of plant growth and development. In our previous study, overexpression of MhSnRK1 in tomato (Solanum lycopersicum L.) modified fruit maturation: the transgenic fruit ripened earlier than the wild type (WT). However, the mechanism by which fruit maturation is regulated by SnRK1 is not clear; therefore, the test materials used were the transgenic tomato lines (OE-1, OE-3, and OE-4) overexpressing the coding gene of peach [Prunus persica (L.) Batsch] SNF1-related kinase α subunit (PpSnRK1α). The activity of SnRK1 kinase in transgenic tomato lines OE-1, OE-3, and OE-4 was higher than that in the WT at different periods of fruit development; in the pink coloring period the SnRK1 kinase activity increased the most, with 23.5, 28.8, and 21.4% increases, respectively. The content of starch and soluble sugars in red ripe transgenic fruit significantly increased, while the soluble protein and titratable acid content decreased significantly. We also found that the tomatoes overexpressing PpSnRK1α matured approximately 10 days earlier than the WT. Moreover, the yeast-two-hybrid assay showed that PpSnRK1α interacted with the MADS-box transcription factor (TF) SIRIN, which acts as an essential regulator of tomato fruit ripening. The BiFC technology further validated the location of the PpSnRK1α interaction sites within the nucleus. The quantitative real-time PCR analysis showed that RIN expression was up-regulated by PpSnRK1α overexpression; the expression of RIN-targeted TF genes NOR and FUL1 increased during different stages of fruit development. The expression of key genes, ACS2, ACS4, and E8, in ethylene synthesis also changed accordingly, and the ethylene emitted by the red ripe fruit increased by 36.1–43.9% compared with the WT. These results suggest that PpSnRK1α interacts with SIRIN, increasing the expression of RIN, thereby regulating the expression of downstream ripening-related genes, finally promoting fruit ripening.

Diacylglycerol acyltransferase 1 is activated by phosphatidate and inhibited by SnRK1-catalyzed phosphorylation.

Diacylglycerol acyltransferase 1 (DGAT1) catalyzes the final and committed step in the Kennedy pathway for triacylglycerol (TAG) biosynthesis and, as such, elucidating its mode of regulation is critical to understand the fundamental aspects of carbon metabolism in oleaginous crops. In this study, purified Brassica napus diacylglycerol acyltransferase 1 (BnaDGAT1) in n-dodecyl-β-d-maltopyranoside micelles was lipidated to form mixed micelles and subjected to detailed biochemical analysis. The degree of mixed micelle fluidity appeared to influence acyltransferase activity. BnaDGAT1 exhibited a sigmoidal response and eventual substrate inhibition with respect to increasing concentrations of oleoyl-CoA. Phosphatidate (PA) was identified as a feed-forward activator of BnaDGAT1, enabling the final enzyme in the Kennedy pathway to adjust to the incoming flow of carbon leading to TAG. In the presence of PA, the oleoyl-CoA saturation plot became more hyperbolic and desensitized to substrate inhibition indicating that PA facilitates the transition of the enzyme into the more active state. PA may also relieve possible autoinhibition of BnaDGAT1 brought about by the N-terminal regulatory domain, which was shown to interact with PA. Indeed, PA is a key effector modulating lipid homeostasis, in addition to its well recognized role in lipid signaling. BnaDGAT1 was also shown to be a substrate of the sucrose non-fermenting-1-related kinase 1 (SnRK1), which catalyzed phosphorylation of the enzyme and converted it to a less active form. Thus, this known regulator of carbon metabolism directly influences TAG biosynthesis.

Sugar-responsive transcription factor bZIP3 affects leaf shape in Arabidopsis plants.

Sugars are essential for plant metabolism, growth and development. Plants must therefore manage their growth and developmental processes in response to sugar availability. Sugar signaling pathways constitute a complicated molecular network and are associated with global transcriptional regulation. However, the molecular mechanisms underlying sugar signaling remain largely unclear. This study reports that the protein basic-region leucine zipper 3 (bZIP3) is a novel sugar-responsive transcription factor in Arabidopsis plants. The expression of bZIP3 was rapidly repressed by sugar. Genetic analysis indicated that bZIP3 expression was modulated by the SNF1-RELATED KINASE 1 (SnRK1) pathway. Moreover, transgenic plants overexpressing bZIP3 and dominant repressor form bZIP3-SRDX showed aberrant shaped cotyledons with hyponastic bending. These findings suggest that bZIP3 plays a role in plant responses to sugars and is also associated with leaf development.

Arabidopsis PCaP2 Functions as a Linker Between ABA and SA Signals in Plant Water Deficit Tolerance.

Water stress has a major influence on plant growth, development, and productivity. However, the cross-talk networks involved in drought tolerance are not well understood. Arabidopsis PCaP2 is a plasma membrane-associated Ca2+-binding protein. In this study, we employ qRT-PCR and β-glucuronidase (GUS) histochemical staining to demonstrate that PCaP2 expression was strongly induced in roots, cotyledons, true leaves, lateral roots, and whole plants under water deficit conditions. Compared with the wild type (WT) plants, PCaP2-overexpressing (PCaP2-OE) plants displayed enhanced water deficit tolerance in terms of seed germination, seedling growth, and plant survival status. On the contrary, PCaP2 mutation and reduction via PCaP2-RNAi rendered plants more sensitive to water deficit. Furthermore, PCaP2-RNAi and pcap2 seedlings showed shorter root hairs and lower relative water content compared to WT under normal conditions and these phenotypes were exacerbated under water deficit. Additionally, the expression of PCaP2 was strongly induced by exogenous abscisic acid (ABA) and salicylic acid (SA) treatments. PCaP2-OE plants showed insensitive to exogenous ABA and SA treatments, in contrast to the susceptible phenotypes of pcap2 and PCaP2-RNAi. It is well-known that SNF1-related kinase 2s (SnRK2s) and pathogenesis-related (PRs) are major factors that influence plant drought tolerance by ABA- and SA-mediated pathways, respectively. Interestingly, PCaP2 positively regulated the expression of drought-inducible genes (RD29A, KIN1, and KIN2), ABA-mediated drought responsive genes (SnRK2.2, -2.3, -2.6, ABF1, -2, -3, -4), and SA-mediated drought responsive genes (PR1, -2, -5) under water deficit, ABA, or SA treatments. Taken together, our results showed that PCaP2 plays an important and positive role in Arabidopsis water deficit tolerance by involving in response to both ABA and SA signals and regulating root hair growth. This study provides novel insights into the underlying cross-talk mechanisms of plants in response to water deficit stress.

Genomic adaptation to drought in wild barley is driven by edaphic natural selection at the Tabigha Evolution Slope

Ecological divergence at a microsite suggests adaptive evolution, and this study examined two abutting wild barley populations, each 100 m across, differentially adapted to drought tolerance on two contrasting soil types, Terra Rossa and basalt at the Tabigha Evolution Slope, Israel. We resequenced the genomes of seven and six wild barley genotypes inhabiting the Terra Rossa and basalt soils, respectively, and identified a total of 69,192,653 single-nucleotide variants (SNVs) and insertions/deletions in comparison with a reference barley genome. Comparative genomic analysis between these abutting wild barley populations involved 19,615,087 high-quality SNVs. The results revealed dramatically different selection sweep regions relevant to drought tolerance driven by edaphic natural selection within 2,577 selected genes in these regions, including key drought-responsive genes associated with ABA synthesis and degradation (such as Cytochrome P450 protein) and ABA receptor complex (such as PYL2, SNF1-related kinase). The genetic diversity of the wild barley population inhabiting Terra Rossa soil is much higher than that from the basalt soil. Additionally, we identified different sets of genes for drought adaptation in the wild barley populations from Terra Rossa soil and from wild barley populations from Evolution Canyon I at Mount Carmel. These genes are associated with abscisic acid signaling, signaling and metabolism of reactive oxygen species, detoxification and antioxidative systems, rapid osmotic adjustment, and deep root morphology. The unique mechanisms for drought adaptation of the wild barley from the Tabigha Evolution Slope may be useful for crop improvement, particularly for breeding of barley cultivars with high drought tolerance.

Snf1-RELATED KINASE1-Controlled C/S1-bZIP Signaling Activates Alternative Mitochondrial Metabolic Pathways to Ensure Plant Survival in Extended Darkness.

Sustaining energy homeostasis is of pivotal importance for all living organisms. In Arabidopsis thaliana, evolutionarily conserved SnRK1 kinases (Snf1-RELATED KINASE1) control metabolic adaptation during low energy stress. To unravel starvation-induced transcriptional mechanisms, we performed transcriptome studies of inducible knockdown lines and found that S1-basic leucine zipper transcription factors (S1-bZIPs) control a defined subset of genes downstream of SnRK1. For example, S1-bZIPs coordinate the expression of genes involved in branched-chain amino acid catabolism, which constitutes an alternative mitochondrial respiratory pathway that is crucial for plant survival during starvation. Molecular analyses defined S1-bZIPs as SnRK1-dependent regulators that directly control transcription via binding to G-box promoter elements. Moreover, SnRK1 triggers phosphorylation of group C-bZIPs and the formation of C/S1-heterodimers and, thus, the recruitment of SnRK1 directly to target promoters. Subsequently, the C/S1-bZIP-SnRK1 complex interacts with the histone acetylation machinery to remodel chromatin and facilitate transcription. Taken together, this work reveals molecular mechanisms underlying how energy deprivation is transduced to reprogram gene expression, leading to metabolic adaptation upon stress.

Gene Regulation and Survival under Hypoxia Requires Starch Availability and Metabolism.

Plants respond to hypoxia, often caused by submergence, by expressing a specific set of genes that contribute to acclimation to this unfavorable environmental condition. Genes induced by low oxygen include those encoding enzymes for carbohydrate metabolism and fermentation, pathways that are required for survival. Sugar availability is therefore of crucial importance for energy production under hypoxia. Here, we show that Arabidopsis (Arabidopsis thaliana) plants require starch for surviving submergence as well as for ensuring the rapid induction of genes encoding enzymes required for anaerobic metabolism. The starchless pgm mutant is highly susceptible to submergence and also fails to induce anaerobic genes at the level of the wild type. Treating wild-type plants under conditions inducing sugar starvation results in a weak induction of alcohol dehydrogenase and other anaerobic genes. Induction of gene expression under hypoxia requires transcription factors belonging to group VII ethylene response factors (ERF-VII) that, together with plant Cys oxidases, act as an oxygen-sensing mechanism. We show that repression of this pathway by sugar starvation occurs downstream of the hypoxia-dependent stabilization of ERF-VII proteins and independently of the energy sensor protein kinases SnRK1.1 (SNF1-related kinase 1.1).

Crystal structure of the kinase and UBA domains of SNRK reveals a distinct UBA binding mode in the AMPK family

Sucrose non-fermenting (Snf1)-related kinase (SNRK) is a novel member of the AMP-activated protein kinase (AMPK) family and is involved in many metabolic processes. Here we report the crystal structure of an N-terminal SNRK fragment containing kinase and adjacent ubiquitin-associated (UBA) domains. This structure shows that the UBA domain binds between the N- and C-lobes of the kinase domain. The mode of UBA binding in SNRK largely resembles that in AMPK and brain specific kinase (BRSK), however, unique interactions play vital roles in stabilizing the KD-UBA interface of SNRK. We further propose a potential role of the UBA domain in the regulation of SNRK kinase activity. This study provides new insights into the structural diversities of the AMPK kinase family.

Regulatory Functions of Cellular Energy Sensor SNF1-Related Kinase1 for Leaf Senescence Delay through ETHYLENE- INSENSITIVE3 Repression

Aging of living organisms is governed by intrinsic developmental programs, of which progression is often under the regulation of their cellular energy status. For example, calorie restriction is known to slow down aging of heterotrophic organisms from yeasts to mammals. In autotrophic plants cellular energy deprivation by perturbation of photosynthesis or sugar metabolism is also shown to induce senescence delay. However, the underlying molecular and biochemical mechanisms remain elusive. Our plant cell-based functional and biochemical assays have demonstrated that SNF1-RELATED KINASE1 (SnRK1) directly interacts, phosphorylates, and destabilizes the key transcription factor ETHYLENE INSENSITIVE3 (EIN3) in senescence-promoting hormone ethylene signaling. Combining chemical manipulation and genetic validation using extended loss-of-function mutants and gain-of-function transgenic lines, we further revealed that a SnRK1 elicitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea enables to slow down senescence-associated leaf degreening through the regulation of EIN3 in Arabidopsis. Our findings enlighten that an evolutionary conserved cellular energy sensor SnRK1 plays a role in fine-tuning of organ senescence progression to avoid sudden death during the last step of leaf growth and development.

MdSnRK1.1 interacts with MdJAZ18 to regulate sucrose-induced anthocyanin and proanthocyanidin accumulation in apple.

Sugars induce anthocyanin biosynthesis in plants. As a conserved energy sensor, SnRK1 (SNF1-related kinase 1) is involved in sucrose-induced anthocyanin accumulation. However, the exact molecular mechanism by which SnRK1 regulates the biosynthesis of anthocyanins and proanthocyanidins (PAs) in response to sucrose in plants is not clear. In this study, it was found that MdSnRK1.1 interacted with MdJAZ18 protein which acts as a repressor in the jasmonate (JA) signaling pathway. MdSnRK1.1 then phosphorylated MdJAZ18 to facilitate its 26S proteasome-mediated degradation, which released MdbHLH3 thereby activating the expression of the regulatory and structural genes, thus finally promoting the biosynthesis of anthocyanins and PAs. Taken together, these results demonstrate the involvement of MdSnRK1.1 in sucrose-induced accumulation of anthocyanins and PAs. For the first time, our findings shed light on the molecular mechanism by which the crosstalk of sucrose and JA signaling regulates flavonoid biosynthesis.

A new link between plant metabolism and circadian rhythms?

A new link between plant metabolism and circadian rhythms?

The metabolic sensor AKIN10 modulates the Arabidopsis circadian clock in a light-dependent manner.

Plants generate rhythmic metabolism during the repetitive day/night cycle. The circadian clock produces internal biological rhythms to synchronize numerous metabolic processes such that they occur at the required time of day. Metabolism conversely influences clock function by controlling circadian period and phase and the expression of core-clock genes. Here, we show that AKIN10, a catalytic subunit of the evolutionarily conserved key energy sensor sucrose non-fermenting 1 (Snf1)-related kinase 1 (SnRK1) complex, plays an important role in the circadian clock. Elevated AKIN10 expression led to delayed peak expression of the circadian clock evening-element GIGANTEA (GI) under diurnal conditions. Moreover, it lengthened clock period specifically under light conditions. Genetic analysis showed that the clock regulator TIME FOR COFFEE (TIC) is required for this effect of AKIN10. Taken together, we propose that AKIN10 conditionally works in a circadian clock input pathway to the circadian oscillator.

The impact of Arabidopsis thaliana SNF1-related-kinase1 (SnRK1)-activating kinase1 (SnAK1) and SnAK2 on SnRK1 phosphorylation status: characterization of a SnAK double mutant.

Arabidopsis thaliana SNF1-related-kinase1 (SnRK1)-activating kinase1 (AtSnAK1) and AtSnAK2 have been shown to phosphorylate invitro and activate the energy signalling integrator, SnRK1. To clarify this signalling cascade inplanta, a genetic- and molecular-based approach was developed. Homozygous single AtSnAK1 and AtSnAK2 T-DNA insertional mutants did not display an apparent phenotype. Crossing of thesingle mutants did not allow the isolation of double-mutant plants, whereas self-pollinating the S1-/-S2+/- sesquimutant specifically gave approximatively 22% individuals in their offspring that, when rescued on sugar-supplemented media invitro, were shown to be AtSnAK1AtSnAK2 double mutants. Interestingly, this was not obtained in the case of the other sesquimutant, S1+/-S2-/-. Although reduced in size, the double mutant had the capacity to produce flowers, but not seeds. Immunological characterization established the T-loop of the SnRK1 catalytic subunit to be non-phosphorylated in the absence of both SnAKs. When the double mutant was complemented with a DNA construct containing an AtSnAK2 open reading frame driven by its own promoter, a normal phenotype was restored. Therefore, wild-type plant growth and development is dependent on the presence of SnAK invivo, and this is correlated with SnRK1 phosphorylation. These data show that both SnAKs are kinases phosphorylating SnRK1, and thereby they contribute to energy signalling inplanta.

Snf1-related kinase improves cardiac mitochondrial efficiency and decreases mitochondrial uncoupling

Ischaemic heart disease limits oxygen and metabolic substrate availability to the heart, resulting in tissue death. Here, we demonstrate that the AMP-activated protein kinase (AMPK)-related protein Snf1-related kinase (SNRK) decreases cardiac metabolic substrate usage and mitochondrial uncoupling, and protects against ischaemia/reperfusion. Hearts from transgenic mice overexpressing SNRK have decreased glucose and palmitate metabolism and oxygen consumption, but maintained power and function. They also exhibit decreased uncoupling protein 3 (UCP3) and mitochondrial uncoupling. Conversely, Snrk knockout mouse hearts have increased glucose and palmitate oxidation and UCP3. SNRK knockdown in cardiac cells decreases mitochondrial efficiency, which is abolished with UCP3 knockdown. We show that Tribbles homologue 3 (Trib3) binds to SNRK, and downregulates UCP3 through PPARα. Finally, SNRK is increased in cardiomyopathy patients, and SNRK reduces infarct size after ischaemia/reperfusion. SNRK also decreases cardiac cell death in a UCP3-dependent manner. Our results suggest that SNRK improves cardiac mitochondrial efficiency and ischaemic protection.

Chitin and Stress Induced Protein Kinase Activation.

The assays described here are pertinent to protein kinase studies in any plant. They include an immunoblot phosphorylation/activation assay and an in-gel activity assay for MAP kinases (MPKs) using the general protein kinase substrate myelin basic protein. They also include a novel in-gel peptide substrate assay for Snf1-related kinase family 2 members (SnRK2s). This kinase family-specific assay overcomes some limitations of in-gel assays and permits the identification of different types of kinase activities in total protein extracts.

Molecular functions of Xanthomonas type III effector AvrBsT and its plant interactors in cell death and defense signaling.

Xanthomonas effector AvrBsT interacts with plant defense proteins and triggers cell death and defense response. This review highlights our current understanding of the molecular functions of AvrBsT and its host interactor proteins. The AvrBsT protein is a member of a growing family of effector proteins in both plant and animal pathogens. Xanthomonas type III effector AvrBsT, a member of the YopJ/AvrRxv family, suppresses plant defense responses in susceptible hosts, but triggers cell death signaling leading to hypersensitive response (HR) and defense responses in resistant plants. AvrBsT interacts with host defense-related proteins to trigger the HR cell death and defense responses in plants. Here, we review and discuss recent progress in understanding the molecular functions of AvrBsT and its host interactor proteins in pepper (Capsicum annuum). Pepper arginine decarboxylase1 (CaADC1), pepper aldehyde dehydrogenase1 (CaALDH1), pepper heat shock protein 70a (CaHSP70a), pepper suppressor of the G2 allele of skp1 (CaSGT1), pepper SNF1-related kinase1 (SnRK1), and Arabidopsis acetylated interacting protein1 (ACIP1) have been identified as AvrBsT interactors in pepper and Arabidopsis. Gene expression profiling, virus-induced gene silencing, and transient transgenic overexpression approaches have advanced the functional characterization of AvrBsT-interacting proteins in plants. AvrBsT is localized in the cytoplasm and forms protein-protein complexes with host interactors. All identified AvrBsT interactors regulate HR cell death and defense responses in plants. Notably, CaSGT1 physically binds to both AvrBsT and pepper receptor-like cytoplasmic kinase1 (CaPIK1) in the cytoplasm. During infection with Xanthomonas campestris pv. vesicatoria strain Ds1 (avrBsT), AvrBsT is phosphorylated by CaPIK1 and forms the active AvrBsT-CaSGT1-CaPIK1 complex, which ultimately triggers HR cell death and defense responses. Collectively, the AvrBsT interactor proteins are involved in plant cell death and immunity signaling.

The plant energy sensor: evolutionary conservation and divergence of SnRK1 structure, regulation, and function.

The SnRK1 (SNF1-related kinase 1) kinases are the plant cellular fuel gauges, activated in response to energy-depleting stress conditions to maintain energy homeostasis while also gatekeeping important developmental transitions for optimal growth and survival. Similar to their opisthokont counterparts (animal AMP-activated kinase, AMPK, and yeast Sucrose Non-Fermenting 1, SNF), they function as heterotrimeric complexes with a catalytic (kinase) α subunit and regulatory β and γ subunits. Although the overall configuration of the kinase complexes is well conserved, plant-specific structural modifications (including a unique hybrid βγ subunit) and associated differences in regulation reflect evolutionary divergence in response to fundamentally different lifestyles. While AMP is the key metabolic signal activating AMPK in animals, the plant kinases appear to be allosterically inhibited by sugar-phosphates. Their function is further fine-tuned by differential subunit expression, localization, and diverse post-translational modifications. The SnRK1 kinases act by direct phosphorylation of key metabolic enzymes and regulatory proteins, extensive transcriptional regulation (e.g. through bZIP transcription factors), and down-regulation of TOR (target of rapamycin) kinase signaling. Significant progress has been made in recent years. New tools and more directed approaches will help answer important fundamental questions regarding their structure, regulation, and function, as well as explore their potential as targets for selection and modification for improved plant performance in a changing environment.

Abstract 12526: Snf1-related Kinase Improves Cardiac Mitochondrial Efficiency by Decreasing Mitochondrial Uncoupling

Introduction: Ischemic heart disease limits oxygen and metabolic substrate availability to the heart, resulting in cardiac tissue death. Snf1-related Kinase (SNRK) is a serine/threonine kinase with sequence similarity to AMP-activated protein kinase, but its function is unknown. We found that SNRK is increased in hearts from patients with ischemic cardiomyopathy, and our gene array data suggested that SNRK alters metabolic genes. Here, we assessed the hypothesis that SNRK improves cardiac metabolic efficiency and mitochondrial uncoupling, and protects against ischemia/reperfusion (I/R) injury. Results: Cardiac-specific SNRK transgenic (TG) mice displayed decreased glycolysis, glucose oxidation, and palmitate oxidation compared to wild type littermate controls in perfused working hearts. However, cardiac power, contractility, ATP, and triglyceride and glycogen stores were maintained, while oxygen consumption was reduced, demonstrating that SNRK TG mice have increased cardiac metabolic efficiency. Consistent with improved cardiac metabolic efficiency, SNRK TG mice exhibited decreased infarct size after I/R. Mitochondria from SNRK TG mice also had reduced respiration, and increased respiratory control ratio and mitochondrial membrane potential, indicating reduced mitochondrial uncoupling. Uncoupling protein 3 (UCP3) levels were also decreased. Conversely, hearts from heterozygous SNRK knockout mice had increased glucose and palmitate oxidation and UCP3. SNRK knockdown in cardiac cells decreased mitochondrial efficiency, which was abolished with UCP3 knockdown. To determine the mechanism for the regulation of UCP3 by SNRK, we performed yeast two-hybrid assay, and identified tribbles homolog 3 (Trib3) to bind to SNRK. Furthermore, Trib3 enabled downregulation of UCP3 by downregulating the expression of PPARα. Conclusions: Our results demonstrate that overexpression of SNRK decreases cardiac metabolic substrate usage and oxygen consumption but maintains cardiac function and enhanced mitochondrial coupling. We also identify a binding partner of SNRK, Trib3, which is upregulated by SNRK in mice and mediates the regulation of PPARα and UCP3 by SNRK.

The SnRK1 Energy Sensor in Plant Biotic Interactions.

Our understanding of plant biotic interactions has grown significantly in recent years with the identification of the mechanisms involved in innate immunity, hormone signaling, and secondary metabolism. The impact of such interactions on primary metabolism and the role of metabolic signals in the response of the plants, however, remain far less explored. The SnRK1 (SNF1-related kinase 1) kinases act as metabolic sensors, integrating very diverse stress conditions, and are key in maintaining energy homeostasis for growth and survival. Consistently, an important role is emerging for these kinases as regulators of biotic stress responses triggered by viral, bacterial, fungal, and oomycete infections as well as by herbivory. While this identifies SnRK1 as a promising target for directed modification or selection for more quantitative and sustainable resistance, its central function also increases the chances of unwanted side effects on growth and fitness, stressing the need for identification and in-depth characterization of the mechanisms and target processes involved. VIDEO ABSTRACT.