scholarly journals Ethylene inhibits stem trichome formation in Arabidopsis

2018 ◽  
Author(s):  
Susan I Gibson
Keyword(s):  
Arabidopsis Thaliana ◽  
Substantial Reduction ◽  
Ethylene Biosynthesis ◽  
Model Systems ◽  
Wild Type ◽  
Normal Numbers ◽  
Biosynthesis Inhibitor ◽  
Ethylene Response ◽  
Normal Differentiation ◽  
Ethylene Insensitivity

Trichomes, specialized cells that form on the above ground parts of plants, are useful model systems for studying cell differentiation. In this study, the plant hormone ethylene was found to strongly inhibit formation of trichomes on stems of Arabidopsis thaliana. Plants grown in the presence of high concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid fail to form trichomes on their primary inflorescences. In addition, plants carrying mutations in CTR1 that confer a constitutive response to ethylene exhibit severe reductions in stem trichome numbers. In contrast, plants carrying mutations that confer ethylene insensitivity, and plants grown in the presence of an ethylene biosynthesis inhibitor, produce normal numbers of stem trichomes. Together, these results suggest that either excess ethylene or a constitutive ethylene response prevents the normal differentiation of cells that would otherwise form stem trichomes. Reduced ethylene levels and decreased ethylene response, in constrast, appear insufficient to cause cells that do not normally form trichomes to form trichomes. In contrast to ethylene, application of exogenous Glc results in increased stem trichome numbers. Besides affecting stem trichome numbers, ethylene may also affect branching of stem trichomes. In Arabidopsis thaliana, the vast majority of stem trichomes are unbranched. When wild-type Arabidiopsis thaliana of the Col-0 ecotype are grown in the presence of an ethylene biosynthesis inhibitor, the percentage of stem trichomes that are branched increases significantly. However, growth in the presence of an ethylene biosynthesis inhibitor does not affect stem branching in wild-type Arabidopsis thaliana of the Ler-0 ecotype. Plants carrying the etr1-1 and ein2-1 mutations, which cause ethylene insensitivity, have an increased percentage of branched stem trichomes. In contrast, plants carrying the ctr1-1 and ctr1-12 mutations have a decreased percentage of branched stem trichomes. Growth in the presence of a precursor of ethylene biosynthesis also causes a substantial reduction in branching of Arabidopsis leaf trichomes, suggesting that ethylene has a negative effect on branching of both leaf and stem trichomes in Arabidopsis.

scholarly journals Ethylene inhibits stem trichome formation in Arabidopsis

2018 ◽  
Author(s):  
Susan I Gibson
Keyword(s):  
Arabidopsis Thaliana ◽  
Substantial Reduction ◽  
Ethylene Biosynthesis ◽  
Model Systems ◽  
Wild Type ◽  
Normal Numbers ◽  
Biosynthesis Inhibitor ◽  
Ethylene Response ◽  
Normal Differentiation ◽  
Ethylene Insensitivity

Trichomes, specialized cells that form on the above ground parts of plants, are useful model systems for studying cell differentiation. In this study, the plant hormone ethylene was found to strongly inhibit formation of trichomes on stems of Arabidopsis thaliana. Plants grown in the presence of high concentrations of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid fail to form trichomes on their primary inflorescences. In addition, plants carrying mutations in CTR1 that confer a constitutive response to ethylene exhibit severe reductions in stem trichome numbers. In contrast, plants carrying mutations that confer ethylene insensitivity, and plants grown in the presence of an ethylene biosynthesis inhibitor, produce normal numbers of stem trichomes. Together, these results suggest that either excess ethylene or a constitutive ethylene response prevents the normal differentiation of cells that would otherwise form stem trichomes. Reduced ethylene levels and decreased ethylene response, in constrast, appear insufficient to cause cells that do not normally form trichomes to form trichomes. In contrast to ethylene, application of exogenous Glc results in increased stem trichome numbers. Besides affecting stem trichome numbers, ethylene may also affect branching of stem trichomes. In Arabidopsis thaliana, the vast majority of stem trichomes are unbranched. When wild-type Arabidiopsis thaliana of the Col-0 ecotype are grown in the presence of an ethylene biosynthesis inhibitor, the percentage of stem trichomes that are branched increases significantly. However, growth in the presence of an ethylene biosynthesis inhibitor does not affect stem branching in wild-type Arabidopsis thaliana of the Ler-0 ecotype. Plants carrying the etr1-1 and ein2-1 mutations, which cause ethylene insensitivity, have an increased percentage of branched stem trichomes. In contrast, plants carrying the ctr1-1 and ctr1-12 mutations have a decreased percentage of branched stem trichomes. Growth in the presence of a precursor of ethylene biosynthesis also causes a substantial reduction in branching of Arabidopsis leaf trichomes, suggesting that ethylene has a negative effect on branching of both leaf and stem trichomes in Arabidopsis.

scholarly journals The Effect of Exogenous Nitrate on LCO Signalling, Cytokinin Accumulation, and Nodule Initiation in Medicago truncatula

Genes ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 988
Author(s):  
Kerstin Gühl ◽  
Rens Holmer ◽  
Ting Ting Xiao ◽  
Defeng Shen ◽  
Titis A. K. Wardhani ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Medicago Truncatula ◽  
Potent Inhibitor ◽  
Ethylene Biosynthesis ◽  
Wild Type ◽  
Biosynthesis Inhibitor ◽  
Signalling Molecules ◽  
Nodule Initiation

Nitrogen fixation by rhizobia is a highly energy-demanding process. Therefore, nodule initiation in legumes is tightly regulated. Environmental nitrate is a potent inhibitor of nodulation. However, the precise mechanism by which this agent (co)regulates the inhibition of nodulation is not fully understood. Here, we demonstrate that in Medicago truncatula the lipo-chitooligosaccharide-induced accumulation of cytokinins is reduced in response to the application of exogenous nitrate. Under permissive nitrate conditions, perception of rhizobia-secreted signalling molecules leads to an increase in the level of four cytokinins (i.e., iP, iPR, tZ, and tZR). However, under high-nitrate conditions, this increase in cytokinins is reduced. The ethylene-insensitive mutant Mtein2/sickle, as well as wild-type plants grown in the presence of the ethylene biosynthesis inhibitor 2-aminoethoxyvinyl glycine (AVG), is resistant to the inhibition of nodulation by nitrate. This demonstrates that ethylene biosynthesis and perception are required to inhibit nodule organogenesis under high-nitrate conditions.

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.

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.

scholarly journals Inhibition of cell expansion enhances cortical microtubule stability in the root apex of Arabidopsis thaliana

2021 ◽  
Vol 28 (1) ◽  
Author(s):  
Veronica Giourieva ◽  
Emmanuel Panteris
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Cell Expansion ◽  
Cortical Microtubule ◽  
Root Apex ◽  
Cellulose Synthase ◽  
Cellulose Biosynthesis ◽  
Cortical Microtubules ◽  
Wild Type ◽  
Microtubule Stability

Abstract Background Cortical microtubules regulate cell expansion by determining cellulose microfibril orientation in the root apex of Arabidopsis thaliana. While the regulation of cell wall properties by cortical microtubules is well studied, the data on the influence of cell wall to cortical microtubule organization and stability remain scarce. Studies on cellulose biosynthesis mutants revealed that cortical microtubules depend on Cellulose Synthase A (CESA) function and/or cell expansion. Furthermore, it has been reported that cortical microtubules in cellulose-deficient mutants are hypersensitive to oryzalin. In this work, the persistence of cortical microtubules against anti-microtubule treatment was thoroughly studied in the roots of several cesa mutants, namely thanatos, mre1, any1, prc1-1 and rsw1, and the Cellulose Synthase Interacting 1 protein (csi1) mutant pom2-4. In addition, various treatments with drugs affecting cell expansion were performed on wild-type roots. Whole mount tubulin immunolabeling was applied in the above roots and observations were performed by confocal microscopy. Results Cortical microtubules in all mutants showed statistically significant increased persistence against anti-microtubule drugs, compared to those of the wild-type. Furthermore, to examine if the enhanced stability of cortical microtubules was due to reduced cellulose biosynthesis or to suppression of cell expansion, treatments of wild-type roots with 2,6-dichlorobenzonitrile (DCB) and Congo red were performed. After these treatments, cortical microtubules appeared more resistant to oryzalin, than in the control. Conclusions According to these findings, it may be concluded that inhibition of cell expansion, irrespective of the cause, results in increased microtubule stability in A. thaliana root. In addition, cell expansion does not only rely on cortical microtubule orientation but also plays a regulatory role in microtubule dynamics, as well. Various hypotheses may explain the increased cortical microtubule stability under decreased cell expansion such as the role of cell wall sensors and the presence of less dynamic cortical microtubules.

scholarly journals PINK1 deficiency impairs adult neurogenesis of dopaminergic neurons

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sarah J. Brown ◽  
Ibrahim Boussaad ◽  
Javier Jarazo ◽  
Julia C. Fitzgerald ◽  
Paul Antony ◽  
...  
Keyword(s):  
Adult Neurogenesis ◽  
Neurodegenerative Disorders ◽  
Dopaminergic Neurons ◽  
Adult Life ◽  
Lineage Tracing ◽  
Model Systems ◽  
Wild Type ◽  
Therapeutic Approaches ◽  
Early Effect ◽  
Early Adult Life

AbstractRecent evidence suggests neurogenesis is on-going throughout life but the relevance of these findings for neurodegenerative disorders such as Parkinson’s disease (PD) is poorly understood. Biallelic PINK1 mutations cause early onset, Mendelian inherited PD. We studied the effect of PINK1 deficiency on adult neurogenesis of dopaminergic (DA) neurons in two complementary model systems. Zebrafish are a widely-used model to study neurogenesis in development and through adulthood. Using EdU analyses and lineage-tracing studies, we first demonstrate that a subset of ascending DA neurons and adjacent local-projecting DA neurons are each generated into adulthood in wild type zebrafish at a rate that decreases with age. Pink1-deficiency impedes DA neurogenesis in these populations, most significantly in early adult life. Pink1 already exerts an early effect on Th1+ progenitor cells rather than on differentiated DA neurons only. In addition, we investigate the effect of PINK1 deficiency in a human isogenic organoid model. Global neuronal differentiation in PINK1-deficient organoids and isogenic controls is similar, but PINK1-deficient organoids display impeded DA neurogenesis. The observation of impaired adult dopaminergic neurogenesis in Pink1 deficiency in two complementing model systems may have significant consequences for future therapeutic approaches in human PD patients with biallelic PINK1 mutations.

Caffeoyl Shikimate Esterase (CSE) Is an Enzyme in the Lignin Biosynthetic Pathway in Arabidopsis

Science ◽  
2013 ◽  
Vol 341 (6150) ◽  
pp. 1103-1106 ◽  
Author(s):  
Ruben Vanholme ◽  
Igor Cesarino ◽  
Katarzyna Rataj ◽  
Yuguo Xiao ◽  
Lisa Sundin ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Walls ◽  
Metabolite Profiling ◽  
Biosynthetic Pathway ◽  
Wild Type ◽  
Secondary Cell Walls ◽  
Phenolic Metabolite ◽  
In The Wild ◽  
Lignin Biosynthetic Pathway

Lignin is a major component of plant secondary cell walls. Here we describe caffeoyl shikimate esterase (CSE) as an enzyme central to the lignin biosynthetic pathway. Arabidopsis thaliana cse mutants deposit less lignin than do wild-type plants, and the remaining lignin is enriched in p-hydroxyphenyl units. Phenolic metabolite profiling identified accumulation of the lignin pathway intermediate caffeoyl shikimate in cse mutants as compared to caffeoyl shikimate levels in the wild type, suggesting caffeoyl shikimate as a substrate for CSE. Accordingly, recombinant CSE hydrolyzed caffeoyl shikimate into caffeate. Associated with the changes in lignin, the conversion of cellulose to glucose in cse mutants increased up to fourfold as compared to that in the wild type upon saccharification without pretreatment. Collectively, these data necessitate the revision of currently accepted models of the lignin biosynthetic pathway.

scholarly journals Behavioral Effects of a Chemorepellent Receptor Knockout Mutation in Tetrahymena thermophila

mSphere ◽  
2017 ◽  
Vol 2 (4) ◽  
Author(s):  
Dianxiong Zou ◽  
Todd M. Hennessey
Keyword(s):  
Receptor Gene ◽  
Classical Model ◽  
Model System ◽  
Model Systems ◽  
Unicellular Eukaryote ◽  
Wild Type ◽  
Inhibitory Neurotransmitter ◽  
In The Wild ◽  
Sensory Responses ◽  
Major Emphasis

ABSTRACT Although many single-cell eukaryotes have served as classical model systems for chemosensory studies for decades, the major emphasis has been on chemoattraction and no chemorepellent receptor gene has been identified in any unicellular eukaryote. This is the first description of a gene that codes for a chemorepellent receptor in any protozoan. Integration of both depolarizing chemorepellent pathways and hyperpolarizing chemoattractant pathways is as important to chemoresponses of motile unicells as excitatory and inhibitory neurotransmitter pathways are to neurons. Therefore, both chemoattractant and chemorepellent pathways should be represented in a useful unicellular model system. Tetrahymena cells provide such a model system because simple behavioral bioassays, gene knockouts, biochemical analysis, and other approaches can be used with these eukaryotic model cells. This work can contribute to the basic understanding of unicellular sensory responses and provide insights into the evolution of chemoreceptors and possible chemorepellent approaches for preventing infections by some pathogenic protozoa. A conditioned supernatant from Tetrahymena thermophila contains a powerful chemorepellent for wild-type cells, and a gene called G37 is required for this response. This is the first genomic identification of a chemorepellent receptor in any eukaryotic unicellular organism. This conditioned supernatant factor (CSF) is small (<1 kDa), and its repellent effect is resistant to boiling, protease treatment, and nuclease digestion. External BAPTA eliminated the CSF response, suggesting that Ca2+ entry is required for the classical avoiding reactions (AR) used for chemorepulsion. A macronuclear G37 gene knockout (G37-KO) mutant is both nonresponsive to the CSF and overresponsive to other repellents such as quinine, lysozyme, GTP, and high potassium concentrations. All of these mutant phenotypes were reversed by overexpression of the wild-type G37 gene in a G37 overexpression mutant. Overexpression of G37 in the wild type caused increased responsiveness to the CSF and underresponsiveness to high K+ concentrations. Behavioral adaptation (by prolonged exposure to the CSF) caused decreases in responsiveness to all of the stimuli used in the wild type and the overexpression mutant but not in the G37-KO mutant. We propose that the constant presence of the CSF causes a decreased basal excitability of the wild type due to chemosensory adaptation through G37 and that all of the G37-KO phenotypes are due to an inability to detect the CSF. Therefore, the G37 protein may be the CSF receptor. The physiological role of these G37-mediated responses may be to both moderate basal excitability and detect the CSF as an indicator of high cell density growth. IMPORTANCE Although many single-cell eukaryotes have served as classical model systems for chemosensory studies for decades, the major emphasis has been on chemoattraction and no chemorepellent receptor gene has been identified in any unicellular eukaryote. This is the first description of a gene that codes for a chemorepellent receptor in any protozoan. Integration of both depolarizing chemorepellent pathways and hyperpolarizing chemoattractant pathways is as important to chemoresponses of motile unicells as excitatory and inhibitory neurotransmitter pathways are to neurons. Therefore, both chemoattractant and chemorepellent pathways should be represented in a useful unicellular model system. Tetrahymena cells provide such a model system because simple behavioral bioassays, gene knockouts, biochemical analysis, and other approaches can be used with these eukaryotic model cells. This work can contribute to the basic understanding of unicellular sensory responses and provide insights into the evolution of chemoreceptors and possible chemorepellent approaches for preventing infections by some pathogenic protozoa.

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