As sessile organisms, plants encounter a variety of environmental stresses and must optimize their growth for survival. Abscisic acid (ABA) and cytokinin antagonistically regulate many developmental ...processes and environmental stress responses in plants. However, the molecular mechanism underlying this antagonism remains poorly defined. In this study, we demonstrated that Sucrose nonfermenting1-related kinases SnRK2.2, SnRK2.3, and SnRK2.6, the key kinases of the ABA signaling pathway, directly interact with and phosphorylate type-A response regulator 5 (ARR5), a negative regulator of cytokinin signaling. The phosphorylation of ARR5 Ser residues by SnRK2s enhanced ARR5 protein stability. Accordingly, plants overexpressing ARR5 showed ABA hypersensitivity and drought tolerance, and these phenotypes could not be recapitulated by overexpressing a non-phosphorylated ARR5 mimic. Moreover, the type-B ARRs, ARR1, ARR11 and ARR12, physically interacted with SnRK2s and repressed the kinase activity of SnRK2.6. The arr1,11,12 triple mutant exhibited hypersensitivity to ABA. Genetic analysis demonstrated that SnRK2s act upstream of ARR5 but downstream of ARR1, ARR11 and ARR12 in mediating ABA response and drought tolerance. Taken together, this study unravels the antagonistic actions of several molecular components of the ABA and cytokinin signaling pathways in mediates drought stress response, providing significant insights into how plants coordinate growth and drought stress response by integrating multiple hormone pathways.
Drought stress is a major environmental factor that limits plant growth and development. Integration of plant hormone signaling networks plays a crucial role in balancing plant growth and stress adaptation. This work revealed the molecular mechanism by which antagonism between ABA and cytokinin signaling mediates plant response to drought stress.
Summary
The plant hormone abscisic acid (ABA) plays a crucial role in regulating seed germination and post‐germination growth. ABSCISIC ACID INSENSITIVE4 (ABI4), an APETALA2 (AP2)‐type transcription ...factor, is required for the ABA‐mediated inhibition of seed germination. Cytokinins promote seed germination and seedling growth by antagonizing ABA signaling. However, the interaction between ABA and cytokinin signaling during seed germination remains unclear. Here, we report that ABA signaling downregulates Arabidopsis response regulators (ARRs), a class of cytokinin‐inducible genes, during seed germination and cotyledon greening. We found that the application of exogenous ABA repressed the expression of type‐A ARRs in Arabidopsis seeds and seedlings. Among the type‐A ARR family members, the expression of ARR6, ARR7 and ARR15 was upregulated in ABA‐deficient mutants, indicating that the transcriptional inhibition of type‐A ARRs requires the ABA signaling pathway. Single and multiple mutations of these ARRs resulted in increased ABA sensitivity during germination and cotyledon greening; overexpression of ARR7 or ARR15 led to an ABA‐insensitive phenotype. These observations suggest that type‐A ARRs inhibit the ABA response during seed germination and cotyledon greening. Further analysis showed that ABI4 negatively regulated the transcription of ARR6, ARR7 and ARR15 by directly binding to their promoters. Genetic analysis showed that loss‐of‐function mutations of ARR7 and ARR15 partially rescued the ABA insensitivity of abi4‐1. Thus, this study revealed that ABI4 plays a key role in ABA and cytokinin signaling by inhibiting the transcription of type‐A ARRs to inhibit seed germination and cotyledon greening.
Significance Statement
The plant hormone abscisic acid (ABA) suppresses seed germination, while cytokinin promotes seed germination and seedling growth. The detailed molecular mechanisms underlying ABA and cytokinin antagonism during seed germination remain elusive. Here we report that the transcription factor ABI4 negatively regulates the expression of Arabidopsis response regulators (ARRs), a class of cytokinin‐inducible genes. Thus ABI4 is a key node that integrates ABA and cytokinin signalling to modulate seed germination and cotyledon greening.
Most patients with anti-glomerular basement membrane (GBM) disease present with rapidly progressive glomerulonephritis, and more than half develop ESKD. Currently, no tools are available to aid in ...the prognostication or management of this rare disease. In one of the largest assembled cohorts of patients with anti-GBM disease (with 174 patients included in the final analysis), the authors demonstrated that the renal risk score for ANCA-associated vasculitis is transferable to anti-GBM disease and the renal histology is strongly predictive of renal survival and recovery. Stratifying patients according to the percentage of normal glomeruli in the kidney biopsy and the need for RRT at the time of diagnosis improves outcome prediction. Such stratification may assist in the management of anti-GBM disease.
Prospective randomized trials investigating treatments and outcomes in anti-glomerular basement membrane (anti-GBM) disease are sparse, and validated tools to aid prognostication or management are lacking.
In a retrospective, multicenter, international cohort study, we investigated clinical and histologic parameters predicting kidney outcome and sought to identify patients who benefit from rescue immunosuppressive therapy. We also explored applying the concept of the renal risk score (RRS), currently used to predict renal outcomes in ANCA-associated vasculitis, to anti-GBM disease.
The final analysis included 174 patients (out of a total of 191). Using Cox and Kaplan-Meier methods, we found that the RRS was a strong predictor for ESKD. The 36-month renal survival was 100%, 62.4%, and 20.7% in the low-risk, moderate-risk, and high-risk groups, respectively. The need for renal replacement therapy (RRT) at diagnosis and the percentage of normal glomeruli in the biopsy were independent predictors of ESKD. The best predictor for renal recovery was the percentage of normal glomeruli, with a cut point of 10% normal glomeruli providing good stratification. A model with the predictors RRT and normal glomeruli ( N ) achieved superior discrimination for significant differences in renal survival. Dividing patients into four risk groups led to a 36-month renal survival of 96.4% (no RRT, N ≥10%), 74.0% (no RRT, N <10%), 42.3% (RRT, N ≥10%), and 14.1% (RRT, N <10%), respectively.
These findings demonstrate that the RRS concept is transferrable to anti-GBM disease. Stratifying patients according to the need for RRT at diagnosis and renal histology improves prediction, highlighting the importance of normal glomeruli. Such stratification may assist in the management of anti-GBM disease.
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This paper proposes a model-based fault diagnosis (FD) approach for wind turbines and its application to a realistic wind turbine FD benchmark. The proposed FD approach combines the use of analytical ...redundancy relations (ARRs) and interval observers. Interval observers consider an unknown but bounded description of the model parametric uncertainty and noise using the the so-called set-membership approach. This approach leads to formulate the fault detection test by means of checking if the measurements fall inside the estimated output interval, obtained from the mathematical model of the wind turbine and noise/parameter uncertainty bounds. Fault isolation is based on considering a set of ARRs obtained from the structural analysis of the wind turbine model and a fault signature matrix that considers the relation of ARRs and faults. The proposed FD approach has been validated on a 5-MW wind turbine using the National Renewable Energy Laboratory FAST simulator. The obtained results are presented and compared with that of other approaches proposed in the literature.
Cytokinins control key aspects of plant growth, including shoot and root meristem development and the timing of senescence of leaves and stems. Cytokinin perception triggers a 2-component signaling ...mechanism that ultimately leads to phosphorylation-dependent activation of a class of transcriptional regulators called type-B ARRs (RRBs). We have recently shown that the stability of the RRB family member ARR1 is increased in response to elevated cytokinin concentrations. In contrast, cytokinin decreases the stability of the closely related RRB member ARR2. The molecular mechanism governing the differential stability regulation of these 2 closely related RRBs remains unknown.
Cytokinins constitute a class of plant hormones influencing numerous aspects of growth and development. These processes occur through the downstream components of the cytokinin signaling pathway ...after its perception and signal transduction. The importance of these downstream signaling components has been revealed through the use of both traditional genetic and advanced molecular approaches studying mutants and transgenic lines involving cytokinin and diverse plant growth and developmental processes. Interestingly, these effects are not always directly via cytokinin, but by interactions with other plants hormones or transcription factor cascades, which can involve regulatory loops that affect transcription as well as hormone concentrations. This review covers recent advancements in understanding the role of cytokinin via its signaling components, specifically the downstream responses regulators in controlling vital plant growth and developmental processes.
Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) causes autoimmune-mediated inflammation of small blood vessels in multiple organs, including the kidneys. The ability to ...accurately predict kidney outcomes would enable a more personalized therapeutic approach.
We used our national renal biopsy registry to validate the ability of ANCA Renal Risk Score (ARRS) to predict end-stage kidney disease (ESKD) for individual patients. This score uses histopathological and biochemical data to stratify patients as high, medium, or low risk for developing ESKD.
A total of 288 patients were eligible for inclusion in the study (low risk n = 144, medium risk n = 122, high risk n = 12). Using adjusted Cox proportional hazard models with the low-risk group as reference, we show that outcome differs between the categories: high-risk hazard ratio (HR) 16.69 (2.91–95.81, P = 0.002); medium risk HR 4.14 (1.07–16.01, P = 0.039). Incremental multivariable-adjusted Cox proportional hazards models demonstrated that adding ARRS to a model adjusted for multiple clinical parameters enhanced predictive discrimination (basic model C-statistic 0.864 95% CI 0.813–0.914, basic model plus ARRS C-statistic 0.877 95% CI 0.823–0.931; P <0.01).
The ARRS better discriminates risk of ESKD in AAV and offers clinicians more prognostic information than the use of standard biochemical and clinical measures alone. This is the first time the ARRS has been validated in a national cohort. The proportion of patients with high-risk scores is lower in our cohort compared to others and should be noted as a limitation of this study.
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Key message
Senescence-associated transcription factor ATAF2 regulates cytokinin signalling and in vitro shoot multiplication in banana plants.
MusaATAF2-
like protein is a stress-related NAC ...transcription factor of banana. It regulates senescence in rooted banana plants. During the early stages of plant development under in vitro conditions, the presence of 6-benzylaminopurine leads to vigorous shoot multiplication. The major contributor to plant shoot multiplication is auxin to cytokinin ratio and their signalling components. The LC–MS analysis of transgenic banana plants overexpressing
MusaATAF2
indicated significantly higher cytokinin content and remarkably lower auxin content. Auxin transport has been reported to be inhibited by flavonoids. Their significantly higher abundance in the shoot tissues in transgenic lines suggested potential negative regulation of auxin signalling in transgenic plants. Enhanced shoot multiplication in transgenic lines was further corroborated by reduced transcript abundance of type-A
Arabidopsis response regulator-like
genes (inhibitors of cytokinin signalling pathway) and higher expression of
Arabidopsis histidine kinase-like
genes and type-B
Arabidopsis response regulator-like
genes (positive regulators of cytokinin signalling pathway) in transgenic lines. Altogether, the data concludes that
MusaATAF2
induces cytokinin hypersensitivity in banana shoots by modulating/regulating the cytokinin signalling components and flavonoids content.
Graphical abstract
In this article, a special type of fault isolation problem is reported where temporal information is required for the estimation of parameters from susceptible fault sub-space. Any physical system ...always obeys certain mathematical constraints under the normal operating condition, and that is incorporated in a behavioral model, which is essentially flowing and force or moment balance. In a fault detection and identification (FDI) model, only concurrent states are known. In FDI, the constraint relationships need to be derived only in terms of known variables, i.e., the measurements and nominal parameters, which are termed analytical redundancy relations (ARRs). The numerical evaluation of ARRs is residuals, and those oscillate within a definite bound of error when computed using test data. In this work, a novel function is formulated using the ARRs at different time instants and that function is minimized to estimate the suspected parameter values belonging to the non-isolable sub-space. Single-fault hypothesis is considered, and a genetic algorithm (GA) is used for the optimization. This FDI analysis may be beneficial for power hydraulic-driven heavy machinery such as hydraulic excavators, dumpers, and front-end loaders, which are mostly used in mines and construction sites.
Lithium‐rich (Li‐rich) manganese‐based layered oxide materials are promising candidates for positive electrode materials due to their high energy density. However, challenges such as transition metal ...cation migration and irreversible anionic redox hinder their application. This study employs various electrochemical methods to systematically investigate three types of cathode materials: LiNi0.6Mn0.2Co0.2O2 (NCM622), Li1.12Ni0.39Mn0.49O2 (Li1.12), and Li1.2Ni0.2Mn0.6O2 (Li1.2). The findings indicate that an increase in lithium content leads to higher participation of anions in Anion Redox Reactions (ARRs), resulting in an augmented capacity. However, this also brings about significant polarization. The activation process of Li‐rich materials triggers the ARRs mechanism, resulting in a sharp increase in resistance. Voltage drops during shelving and cycling are closely tied to the ARRs occurring at high potentials in Li‐rich materials. To make the best use of the additional capacity associated with ARRs, it is essential to adjust the formation/cycling voltage in accordance with the characteristics of positive electrode materials with varying lithium contents. This study offers valuable insights for the design and utilization of Li‐rich materials.
This study uses electrochemical techniques to examine three cathode materials. It finds that increased lithium content boosts Anion Redox Reactions (ARRs), enhancing capacity but causing polarization. Activation of Li‐rich materials triggers ARRs, raising resistance. Voltage drops are tied to ARRs in Li‐rich materials. Adjusting voltage is key for harnessing extra capacity from ARRs. The research provides valuable insights for the design and use of Li‐rich materials.
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