scholarly journals A loss-of-function mutation in the nucleoporin AtNUP160 indicates that normal auxin signalling is required for a proper ethylene response in Arabidopsis

2012 ◽  
Vol 63 (5) ◽  
pp. 2231-2241 ◽  
Author(s):  
L. M. Robles ◽  
S. D. Deslauriers ◽  
A. A. Alvarez ◽  
P. B. Larsen
Keyword(s):  
Loss Of Function ◽  
Ethylene Response ◽  
Auxin Signalling

scholarly journals Membrane protein MHZ3 stabilizes OsEIN2 in rice by interacting with its Nramp-like domain

2018 ◽  
Vol 115 (10) ◽  
pp. 2520-2525 ◽  
Author(s):  
Biao Ma ◽  
Yang Zhou ◽  
Hui Chen ◽  
Si-Jie He ◽  
Yi-Hua Huang ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Ethylene Signaling ◽  
Loss Of Function ◽  
Wild Type ◽  
Protein Ubiquitination ◽  
Ethylene Response ◽  
Gene And Protein Expression ◽  
Domain Loss ◽  
Ethylene Insensitivity ◽  
Insight Into

The phytohormone ethylene regulates many aspects of plant growth and development. EIN2 is the central regulator of ethylene signaling, and its turnover is crucial for triggering ethylene responses. Here, we identified a stabilizer of OsEIN2 through analysis of the rice ethylene-response mutant mhz3. Loss-of-function mutations lead to ethylene insensitivity in etiolated rice seedlings. MHZ3 encodes a previously uncharacterized membrane protein localized to the endoplasmic reticulum. Ethylene induces MHZ3 gene and protein expression. Genetically, MHZ3 acts at the OsEIN2 level in the signaling pathway. MHZ3 physically interacts with OsEIN2, and both the N- and C-termini of MHZ3 specifically associate with the OsEIN2 Nramp-like domain. Loss of mhz3 function reduces OsEIN2 abundance and attenuates ethylene-induced OsEIN2 accumulation, whereas MHZ3 overexpression elevates the abundance of both wild-type and mutated OsEIN2 proteins, suggesting that MHZ3 is required for proper accumulation of OsEIN2 protein. The association of MHZ3 with the Nramp-like domain is crucial for OsEIN2 accumulation, demonstrating the significance of the OsEIN2 transmembrane domains in ethylene signaling. Moreover, MHZ3 negatively modulates OsEIN2 ubiquitination, protecting OsEIN2 from proteasome-mediated degradation. Together, these results suggest that ethylene-induced MHZ3 stabilizes OsEIN2 likely by binding to its Nramp-like domain and impeding protein ubiquitination to facilitate ethylene signal transduction. Our findings provide insight into the mechanisms of ethylene signaling.

scholarly journals Molecular framework for TIR1/AFB-Aux/IAA-dependent auxin sensing controlling adventitious rooting in Arabidopsis

2019 ◽  
Author(s):  
Abdellah Lakehal ◽  
Salma Chaabouni ◽  
Emilie Cavel ◽  
Rozenn Le Hir ◽  
Alok Ranjan ◽  
...  
Keyword(s):  
Indole Acetic Acid ◽  
Root Formation ◽  
Adventitious Rooting ◽  
Adventitious Root Formation ◽  
Loss Of Function ◽  
Auxin Response ◽  
Genetic Studies ◽  
Auxin Signalling ◽  
Positive Regulators ◽  
Molecular Framework

ABSTRACTIn Arabidopsis thaliana, canonical auxin-dependent gene regulation is mediated by 23 transcription factors from the AUXIN RESPONSE FACTOR (ARF) family interacting with 29 auxin/indole acetic acid repressors (Aux/IAA), themselves forming coreceptor complexes with one of six TRANSPORT INHIBITOR1/AUXIN-SIGNALLING F-BOX (TIR1/AFB) PROTEINS. Different combinations of co-receptors drive specific sensing outputs, allowing auxin to control a myriad of processes. Considerable efforts have been made to discern the specificity of auxin action. However, owing to a lack of obvious phenotype in single loss-of-function mutants in Aux/IAA genes, most genetic studies have relied on gain-of-function mutants, which are highly pleiotropic. Using loss-of-function mutants, we show that three Aux/IAA proteins interact with ARF6 and/or ARF8, which we have previously shown to be positive regulators of AR formation upstream of jasmonate, and likely repress their activity. We also demonstrate that TIR1 and AFB2 are positive regulators of adventitious root formation and suggest a dual role for TIR1 in the control of JA biosynthesis and conjugation, as revealed by upregulation of several JA biosynthesis genes in the tir1-1 mutant. We propose that in the presence of auxin, TIR1 and AFB2 form specific sensing complexes with IAA6, IAA9 and/or IAA17 that modulate JA homeostasis to control AR initiation.

scholarly journals Auxin regulates SNARE-dependent vacuolar morphology restricting cell size

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Christian Löfke ◽  
Kai Dünser ◽  
David Scheuring ◽  
Jürgen Kleine-Vehn
Keyword(s):  
Cell Wall ◽  
Cell Size ◽  
Growth Regulation ◽  
Cellular Growth ◽  
Protein Abundance ◽  
Loss Of Function ◽  
Organ Growth ◽  
Auxin Signalling ◽  
Dependent Growth ◽  
Auxin Effect

The control of cellular growth is central to multicellular patterning. In plants, the encapsulating cell wall literally binds neighbouring cells to each other and limits cellular sliding/migration. In contrast to its developmental importance, growth regulation is poorly understood in plants. Here, we reveal that the phytohormone auxin impacts on the shape of the biggest plant organelle, the vacuole. TIR1/AFBs-dependent auxin signalling posttranslationally controls the protein abundance of vacuolar SNARE components. Genetic and pharmacological interference with the auxin effect on vacuolar SNAREs interrelates with auxin-resistant vacuolar morphogenesis and cell size regulation. Vacuolar SNARE VTI11 is strictly required for auxin-reliant vacuolar morphogenesis and loss of function renders cells largely insensitive to auxin-dependent growth inhibition. Our data suggests that the adaptation of SNARE-dependent vacuolar morphogenesis allows auxin to limit cellular expansion, contributing to root organ growth rates.

E3 ubiquitin ligases

2005 ◽  
Vol 41 ◽  
pp. 15-30 ◽  
Author(s):  
Helen C. Ardley ◽  
Philip A. Robinson
Keyword(s):  
Protein Complexes ◽  
Loss Of Function ◽  
Direct Role ◽  
Cellular Processes ◽  
Substrate Protein ◽  
Protein Ubiquitination ◽  
C Terminus ◽  
Full Complement ◽  
Spatio Temporal ◽  
Eukaryotic Organisms

The selectivity of the ubiquitin–26 S proteasome system (UPS) for a particular substrate protein relies on the interaction between a ubiquitin-conjugating enzyme (E2, of which a cell contains relatively few) and a ubiquitin–protein ligase (E3, of which there are possibly hundreds). Post-translational modifications of the protein substrate, such as phosphorylation or hydroxylation, are often required prior to its selection. In this way, the precise spatio-temporal targeting and degradation of a given substrate can be achieved. The E3s are a large, diverse group of proteins, characterized by one of several defining motifs. These include a HECT (homologous to E6-associated protein C-terminus), RING (really interesting new gene) or U-box (a modified RING motif without the full complement of Zn2+-binding ligands) domain. Whereas HECT E3s have a direct role in catalysis during ubiquitination, RING and U-box E3s facilitate protein ubiquitination. These latter two E3 types act as adaptor-like molecules. They bring an E2 and a substrate into sufficiently close proximity to promote the substrate's ubiquitination. Although many RING-type E3s, such as MDM2 (murine double minute clone 2 oncoprotein) and c-Cbl, can apparently act alone, others are found as components of much larger multi-protein complexes, such as the anaphase-promoting complex. Taken together, these multifaceted properties and interactions enable E3s to provide a powerful, and specific, mechanism for protein clearance within all cells of eukaryotic organisms. The importance of E3s is highlighted by the number of normal cellular processes they regulate, and the number of diseases associated with their loss of function or inappropriate targeting.

Mechanisms of ethylene biosynthesis and response in plants

2015 ◽  
Vol 58 ◽  
pp. 61-70 ◽  
Author(s):  
Paul B. Larsen
Keyword(s):  
Plant Growth ◽  
Growth And Development ◽  
Ethylene Biosynthesis ◽  
Unsaturated Hydrocarbon ◽  
Flower Senescence ◽  
Detailed Knowledge ◽  
Plant Growth And Development ◽  
Step Process ◽  
Ethylene Response ◽  
Ethylene Signalling

Ethylene is the simplest unsaturated hydrocarbon, yet it has profound effects on plant growth and development, including many agriculturally important phenomena. Analysis of the mechanisms underlying ethylene biosynthesis and signalling have resulted in the elucidation of multistep mechanisms which at first glance appear simple, but in fact represent several levels of control to tightly regulate the level of production and response. Ethylene biosynthesis represents a two-step process that is regulated at both the transcriptional and post-translational levels, thus enabling plants to control the amount of ethylene produced with regard to promotion of responses such as climacteric flower senescence and fruit ripening. Ethylene production subsequently results in activation of the ethylene response, as ethylene accumulation will trigger the ethylene signalling pathway to activate ethylene-dependent transcription for promotion of the response and for resetting the pathway. A more detailed knowledge of the mechanisms underlying biosynthesis and the ethylene response will ultimately enable new approaches to be developed for control of the initiation and progression of ethylene-dependent developmental processes, many of which are of horticultural significance.

Metallic prions

2004 ◽  
Vol 71 ◽  
pp. 193-202 ◽  
Author(s):  
David R Brown
Keyword(s):  
Prion Protein ◽  
Binding Capacity ◽  
Normal Function ◽  
Transmissible Spongiform Encephalopathies ◽  
Published Data ◽  
Normal Brain ◽  
Copper Binding ◽  
Loss Of Function ◽  
Spongiform Encephalopathies ◽  
The Brain

Prion diseases, also referred to as transmissible spongiform encephalopathies, are characterized by the deposition of an abnormal isoform of the prion protein in the brain. However, this aggregated, fibrillar, amyloid protein, termed PrPSc, is an altered conformer of a normal brain glycoprotein, PrPc. Understanding the nature of the normal cellular isoform of the prion protein is considered essential to understanding the conversion process that generates PrPSc. To this end much work has focused on elucidation of the normal function and activity of PrPc. Substantial evidence supports the notion that PrPc is a copper-binding protein. In conversion to the abnormal isoform, this Cu-binding activity is lost. Instead, there are some suggestions that the protein might bind other metals such as Mn or Zn. PrPc functions currently under investigation include the possibility that the protein is involved in signal transduction, cell adhesion, Cu transport and resistance to oxidative stress. Of these possibilities, only a role in Cu transport and its action as an antioxidant take into consideration PrPc's Cu-binding capacity. There are also more published data supporting these two functions. There is strong evidence that during the course of prion disease, there is a loss of function of the prion protein. This manifests as a change in metal balance in the brain and other organs and substantial oxidative damage throughout the brain. Thus prions and metals have become tightly linked in the quest to understand the nature of transmissible spongiform encephalopathies.

Errata

2008 ◽  
Vol 13 (2) ◽  
pp. 5-5
Keyword(s):  
Psychotic Disorders ◽  
Pain Syndrome ◽  
Vestibular Disorders ◽  
Loss Of Function ◽  
Sixth Edition ◽  
Neurologic Disorders ◽  
Upper And Lower Extremities ◽  
Impairment Ratings ◽  
Extensive List ◽  
Mental And Behavioral Disorders

Abstract Although most chapters in the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Sixth Edition, instruct evaluators to perform impairment ratings by first assigning a diagnosis-based class and then assigning a grade within that class, Chapter 13, The Central and Peripheral Nervous System, continues to use a methodology similar to that of the fifth edition. The latter was criticized for duplicating materials that were presented in other chapters and for producing different ratings, so the revision of Chapter 13 attempts to maintain consistency between this chapter and those that address mental and behavioral disorders, loss of function in upper and lower extremities, loss of bowel control, and bladder and sexual function. A table titled Summary of Chapters Used to Rate Various Neurologic Disorders directs physicians to the relevant chapters (ie, instead of Chapter 13) to consult in rating neurologic disorders; the extensive list of conditions that should be addressed in other chapters includes but is not limited to radiculopathy, plexus injuries and other plexopathies, focal neuropathy, complex regional pain syndrome, visual and vestibular disorders, and a range of primary mood, anxiety, and psychotic disorders. The article comments in detail on sections of this chapter, identifies changes in the sixth edition, and provide guidance regarding use of the new edition, resulting in less duplication and greater consistency.

Impairment Tutorial: Rating Facial Disfigurement After an Injury

1998 ◽  
Vol 3 (4) ◽  
pp. 6-6
Author(s):  
Marc T. Taylor
Keyword(s):  
Current Work ◽  
Workers Compensation ◽  
Loss Of Function ◽  
Facial Disfigurement ◽  
Work Related ◽  
Work Related Injury ◽  
Compensation Claim ◽  
Impairment Ratings

Abstract This article discusses two important cases that involve the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides). First, in Vargas v Industrial Com’n of Arizona, a claimant had a pre-existing non–work-related injury to his right knee as well as a work-related injury, and the issue was apportionment of the pre-existing injury. The court held that, under Arizona's statute, the impairment from the pre-existing injury should be subtracted from the current work-related impairment. In the second case, Colorado courts addressed the issue of apportionment in a workers’ compensation claim in which the pre-existing injury was asymptomatic at the time of the work-related injury (Askey v Industrial Claim Appeals Office). In this case, the court held that the worker's benefits should not be reduced to account for an asymptomatic pre-existing condition that could not be rated accurately using the AMA Guides. The AMA Guides bases impairment ratings on anatomic or physiologic loss of function, and if an examinee presents with two or more sequential injuries and calculable impairments, the AMA Guides can be used to apportion between pre-existing and subsequent impairments. Courts often use the AMA Guides to decide statutorily determined benefits and are subject to interpretation by courts and administrative bodies whose interpretations may vary from state to state.

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