We review current knowledge on the involvement of SnRK1 and TOR in plant responses to biotic and abiotic stress, particularly focusing on their contribution to growth-defense trade-offs.
Abstract
The ...evolutionarily conserved protein kinase complexes SnRK1 and TOR are central metabolic regulators essential for plant growth, development, and stress responses. They are activated by opposite signals, and the outcome of their activation is, in global terms, antagonistic. Similarly to their yeast and animal counterparts, SnRK1 is activated by the energy deficit often associated with stress to restore homeostasis, while TOR is activated in nutrient-rich conditions to promote growth. Recent evidence suggests that SnRK1 represses TOR in plants, revealing evolutionary conservation also in their crosstalk. Given their importance for integrating environmental information into growth and developmental programs, these signaling pathways hold great promise for reducing the growth penalties caused by stress. Here we review the literature connecting SnRK1 and TOR to plant stress responses. Although SnRK1 and TOR emerge mostly as positive regulators of defense and growth, respectively, the outcome of their activities in plant growth and performance is not always straightforward. Manipulation of both pathways under similar experimental setups, as well as further biochemical and genetic analyses of their molecular and functional interaction, is essential to fully understand the mechanisms through which these two metabolic pathways contribute to stress responses, growth, and development.
•Sugars serve as nutrients and as regulatory signals.•SnRK1 and TOR control metabolism and growth oppositely in response to sugars.•Manipulation of SnRK1 and TOR results in highly diverse ...developmental phenotypes.•Sugar signals shape plant development via SnRK1 and TOR.
SnRK1 (Snf1-related protein kinase 1) and TOR (target of rapamycin) are evolutionarily conserved protein kinases that lie at the heart of energy sensing, playing central and antagonistic roles in the regulation of metabolism and gene expression. Increasing evidence links these metabolic regulators to numerous aspects of plant development, from germination to flowering and senescence. This prompts the hypothesis that SnRK1 and TOR modify developmental programs according to the metabolic status to adjust plant growth to a specific environment. The aim of this review is to provide support to this hypothesis and to incentivize further studies on this topic by summarizing the work that establishes a genetic connection between SnRK1–TOR and plant development.
Abstract
Context
Denosumab discontinuation is characterized by an increase in bone turnover overriding pretreatment status, a rapid bone loss in the majority and multiple vertebral fractures (VFx) in ...some patients.
Methods
A working group of the European Calcified Tissue Society performed an updated systematic review of existing literature on changes of bone turnover, bone mineral density (BMD), and fracture risk after denosumab discontinuation and provided advice on management based on expert opinion.
Results
Important risk factors for multiple VFx following denosumab cessation are prevalent VFx, longer duration off therapy, greater gain in hip BMD during therapy, and greater loss of hip BMD after therapy according to a retrospective analysis of the FREEDOM Extension Study. Case series indicate that prior bisphosphonate therapy mitigates the biochemical rebound phenomenon after denosumab discontinuation, but it is uncertain whether this attenuation prevents BMD loss and fractures. Current evidence indicates partial efficacy of subsequent antiresorptive treatment with results seemingly dependent on duration of denosumab treatment.
Conclusions
A careful assessment of indications to start denosumab treatment is advised, especially for younger patients. A case for long-term treatment with denosumab can be made for patients at high fracture risk already on denosumab treatment given the favorable efficacy and safety profile. In case of denosumab discontinuation, alternative antiresorptive treatment should be initiated 6 months after the final denosumab injection. Assessment of bone turnover markers may help define the optimal regimen, pending results of ongoing randomized controlled trials. Patients who have sustained VFx should be offered prompt treatment to reduce high bone turnover.
Plants are constantly confronted by multiple types of stress. Despite their distinct origin and mode of perception, nutrient deprivation and most stresses have an impact on the overall energy status ...of the plant, leading to convergent downstream responses that include largely overlapping transcriptional patterns. The emerging view is that this transcriptome reprogramming in energy and stress signaling is partly regulated by the evolutionarily conserved energy sensor protein kinases, SNF1 (sucrose non-fermenting 1) in yeast, AMPK (AMP-activated protein kinase) in mammals and SnRK1 (SNF1-related kinase 1) in plants. Upon sensing the energy deficit associated with stress, nutrient deprivation and darkness, SnRK1 triggers extensive transcriptional changes that contribute to restoring homeostasis, promoting cell survival and elaborating longer-term responses for adaptation, growth and development.
SUCROSE NON-FERMENTING1 (SNF1)-RELATED KINASE 1 (SnRK1) is an evolutionarily conserved protein kinase with key roles in plant stress responses. SnRK1 is activated when energy levels decline during ...stress, reconfiguring metabolism and gene expression to favour catabolism over anabolism, and ultimately to restore energy balance and homeostasis. The capacity to efficiently redistribute resources is crucial to cope with adverse environmental conditions, and accordingly, genetic manipulations that increase SnRK1 activity are generally associated with enhanced tolerance to stress. In addition to its well-established function in stress responses, an increasing number of studies implicate SnRK1 in the homeostatic control of metabolism during the regular day-night cycle and in different organs and developmental stages. Here, we review how the genetic manipulation of SnRK1 alters central metabolism in several plant species and tissue types. We complement this with studies that provide mechanistic insight into how SnRK1 modulates metabolism, identifying changes in transcripts of metabolic components, altered enzyme activities or direct regulation of enzymes or transcription factors by SnRK1 via phosphorylation. We identify patterns of response that centre on the maintenance of sucrose levels, in an analogous manner to the role described for its mammalian ortholog in the control of blood glucose homeostasis. Finally, we highlight several knowledge gaps and technical limitations that will have to be addressed in future research aiming to fully understand how SnRK1 modulates metabolism at the cellular and whole plant levels.
Tear Based Bioelectronics Pankratov, Dmitry; González-Arribas, Elena; Blum, Zoltan ...
Electroanalysis (New York, N.Y.),
June 2016, Letnik:
28, Številka:
6
Journal Article
Recenzirano
This work provides an overview of the recent advances in the field of tear‐based wearable electrochemical biodevices, including non‐invasive biosensors, biological fuel cells and biosupercapacitors. ...Contact lenses are attractive platforms for fabricating non‐invasive self‐contained gadgets for different applications, starting from devices with casual or mundane purposes only, like personalized smart lenses with direct (invisible for others) displays, and ending with biomedical devices for continuous fitness status and/or health care monitoring. Key requirements and challenges that confront researchers in this exciting area are discussed.
Gene delivery is a complex process with several challenges when attempting to incorporate genetic material efficiently and safely into target cells. Some of the key challenges include not only ...efficient cellular uptake and endosomal escape to ensure that the genetic material can exert its effect but also minimizing the toxicity of the delivery system, which is vital for safe gene delivery. Of importance, if gene delivery systems are intended for biomedical applications or clinical use, they must be scalable and easy and affordable to manufacture to meet the demand. Here, we show an efficient gene delivery method using a combination of carbon dots coated by PEI through electrostatic binding to easily generate cationic carbon dots. We show a biofunctional approach to generate optimal cationic carbon dots (CCDs) that can be scaled up to meet specific transfection demands. CCDs improve cell viability and increase transfection efficiency four times over the standard of PEI polyplexes. Generated CCDs enabled the challenging transfection protocol to produce retroviral vectors via cell cotransfection of three different plasmids into packing cells, showing not only high efficiency but also functionality of the gene delivery, tested as the capacity to produce infective retroviral particles.
The phytohormone abscisic acid (ABA) promotes plant tolerance to major stresses such as drought, partly by modulating growth through poorly understood mechanisms. Here, we show that ABA-triggered ...repression of cell proliferation in the
Arabidopsis thaliana
root meristem relies on the swift subcellular relocalization of SNF1-RELATED KINASE 1 (SnRK1). Under favorable conditions, the SnRK1 catalytic subunit, SnRK1α1, is enriched in the nuclei of root cells, and this is accompanied by normal cell proliferation and meristem size. Depletion of two key drivers of ABA signaling, SnRK2.2 and SnRK2.3, causes constitutive cytoplasmic localization of SnRK1α1 and reduced meristem size, suggesting that, under nonstress conditions, SnRK2s promote growth by retaining SnRK1α1 in the nucleus. In response to ABA, SnRK1α1 translocates to the cytoplasm, and this is accompanied by inhibition of target of rapamycin (TOR), decreased cell proliferation, and reduced meristem size. Blocking nuclear export with leptomycin B abrogates ABA-driven SnRK1α1 relocalization to the cytoplasm and ABA-elicited inhibition of TOR. Furthermore, fusing SnRK1α1 to an SV40 nuclear localization signal leads to defective ABA-dependent TOR repression. Altogether, we demonstrate that SnRK2-dependent changes in SnRK1α1 subcellular localization are crucial for inhibiting TOR and root growth in response to ABA. Rapid relocalization of central regulators such as SnRK1 may represent a general strategy of eukaryotic organisms to respond to environmental changes.
Abstract
Context
After menopause, fat mass (FM) and visceral adipose tissue (VAT) increase and nonbone lean body mass (LBM) decreases. Whether menopausal hormone therapy (MHT) reverses these changes ...remains controversial.
Objective
To assess the effect of MHT on FM, VAT, and LBM before and after its withdrawal and evaluate potential confounders.
Design
Cross-sectional study.
Setting
General community.
Patients or Other Participants
Women of the OsteoLaus cohort (50 to 80 years old) who underwent dual-energy X-ray absorptiometry (DXA) with body composition assessment. After we excluded women with estrogen-modifying medications, the 1053 participants were categorized into current users (CUs), past users (PUs), and never users (NUs) of MHT.
Intervention
None.
Main Outcome Measures
VAT measured by DXA was the primary outcome. We assessed subtotal and android FM, LBM, muscle strength (hand grip), and confounding factors (caloric intake, physical activity, biomarkers).
Results
The groups significantly differed in age, NU < CU < PU. Age-adjusted VAT was lower in CUs than NUs (P = 0.03). CUs exhibited lower age-adjusted body mass index (BMI) (−0.9 kg/m2) and a trend for lower FM (−1.3 kg). The 10-year gain of VAT (P < 0.01) and subtotal and android FM (P < 0.05) was prevented in CUs. No difference in LBM or hand grip was detected. No residual effect was detected for PUs, including for early MHT discontinuers. The confounding factors did not significantly differ between groups except for higher caloric intake in PUs compared with NUs.
Conclusions
MHT is associated with significantly decreased VAT, BMI, and android FM. No benefit is detected for LBM. The benefits are not preserved in PUs, suggesting caution when MHT is discontinued.
Menopausal hormone therapy is associated with decreased visceral adipose tissue and prevention of the age-associated gain of fat mass. These benefits are not preserved in past users.
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