scholarly journals Nitrate inhibition of nodule formation in Medicago truncatula is mediated by ACC SYNTHASE 10

2018 ◽  
Author(s):  
Arjan van Zeijl ◽  
Kerstin Guhl ◽  
Ting Ting Xiao ◽  
Defeng Shen ◽  
René Geurts ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Acc Synthase ◽  
Ethylene Biosynthesis ◽  
Nodule Formation ◽  
Signalling Molecules ◽  
Rate Limiting Step ◽  
One Step ◽  
Nitrate Inhibition ◽  
Nodule Initiation ◽  
Rate Limiting

ABSTRACTLegumes form a mutualistic endosymbiosis with nitrogen-fixing rhizobia. These rhizobia are housed intracellularly in specialised lateral root organs, called nodules. Initiation of these nodules is triggered by bacterial derived signalling molecules, lipochitooligosaccharides (LCO). The process of nitrogen fixation is highly energy-demanding and therefore nodule initiation is tightly regulated. Nitrate is a potent inhibitor of nodulation. However, the precise mechanisms by which nitrate inhibits nodulation is poorly understood. Here, we demonstrate that in Medicago truncatula nitrate interferes with the transcriptional regulation of the ethylene biosynthesis gene ACC SYNTHASE 10. ACSs commit the rate limiting step in ethylene biosynthesis and in M. truncatula ACS10 is highly expressed in the zone of the root where nodulation occurs. Our results show that a reduction in ACS10 expression in response to LCO exposure correlates with the ability to form nodules. In addition, RNAi-mediated knockdown of ACS10 confers nodulation ability under otherwise inhibitory nitrate conditions. This discovery sheds new light on how ethylene is involved in the inhibition of nodulation by nitrate, bringing us one step closer to understanding how plants regulate their susceptibility towards rhizobia.

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 Cloning the mRNA encoding 1-aminocyclopropane-1-carboxylate synthase, the key enzyme for ethylene biosynthesis in plants

1989 ◽  
Vol 86 (17) ◽  
pp. 6621-6625 ◽  
Author(s):  
T Sato ◽  
A Theologis
Keyword(s):  
Plant Hormone ◽  
Acc Synthase ◽  
Ethylene Biosynthesis ◽  
In Vivo Studies ◽  
Rate Limiting Step ◽  
Ethylene Precursor ◽  
Key Enzyme ◽  
Sequence Encoding ◽  
Rate Limiting

Ethylene is the plant hormone that controls several features of plant growth and development. The rate-limiting step in its synthesis is the formation of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) from S-adenosylmethionine (AdoMet), catalyzed by ACC synthase. We have isolated a complementary DNA sequence encoding ACC synthase from zucchini (Cucurbita) fruits. The biological activity of the clone was confirmed by the ability of the cloned sequence to direct ACC synthase activity in Escherichia coli and yeast. In vivo studies using the ACC cDNA as probe showed that the ACC synthase gene is induced by a diverse group of inducers, including wounding, Li+ ions, and the plant hormone auxin.

scholarly journals A Positive Role for Rhizobitoxine in Rhizobium-legume Symbiosis

1999 ◽  
Vol 12 (12) ◽  
pp. 1082-1089 ◽  
Author(s):  
Samuel Duodu ◽  
T. V. Bhuvaneswari ◽  
Thomas J. W. Stokkermans ◽  
N. Kent Peters
Keyword(s):  
Ethylene Biosynthesis ◽  
Nodule Development ◽  
Ethylene Inhibitors ◽  
Wild Type ◽  
Positive Role ◽  
Rate Limiting Step ◽  
Mutant Strains ◽  
Legume Symbiosis ◽  
Exogenous Ethylene ◽  
Rate Limiting

Although Bradyrhizobium elkanii is a mutualistic symbiont of legumes, it synthesizes a phytotoxin, rhizobitoxine, that causes chlorosis on a variety of legume hosts, giving a pathogenic character to these interactions. No positive role for rhizobitoxine has been previously demonstrated. Interestingly, rhizobitoxine inhibits the rate-limiting step for ethylene biosynthesis, a plant hormone known to inhibit or down-regulate nodule development. We hypothesized that rhizobitoxine plays a positive role in nodule development through its inhibition of ethylene biosynthesis. To test this hypothesis, host plants of B. elkanii were screened for a differential nodulation response to the wild-type and rhizobitoxine mutant strains. In Vigna radiata (mungbean), the rhizobitoxine mutant strains induced many aborted nodules arrested at all stages of pre-emergent and post-emergent development and formed significantly fewer mature nodules than the wild type. Experiments revealed that nodulation of mungbean plants is sensitive to exogenous ethylene, and that the ethylene inhibitors aminoethoxyvinylglycine and Co2+ were able to partially restore a wild-type nodulation pattern to the rhizobitoxine mutants. This is the first demonstration of a nodulation phenotype of the rhizobitoxine mutants and suggests that rhizobitoxine plays a positive and necessary role in Rhizobium-legume symbiosis through its inhibition of ethylene biosynthesis.

scholarly journals Control of the flux in the arginine pathway of Neurospora crassa. Modulations of enzyme activity and concentration

1981 ◽  
Vol 200 (2) ◽  
pp. 231-246 ◽  
Author(s):  
H J Flint ◽  
R W Tateson ◽  
I B Barthelmess ◽  
D J Porteous ◽  
W D Donachie ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Enzyme Activities ◽  
Genetic Recombination ◽  
Quantitative Measure ◽  
Sensitivity Coefficient ◽  
Mass Action ◽  
Rate Limiting Step ◽  
One Step ◽  
Rate Limiting ◽  
Different Parts

The influence of particular enzyme activities on the flux of metabolites in a pathway can be estimated by ‘modulating’ enzymes (i.e. changing turnover or concentration) and measuring the response in various parts of the system. By controlling the nuclear ration of two genetically different nuclear types in heterokaryons, the enzyme concentrations at four different steps in the arginine pathway were decreased over a range. This range was extended by the use of bradytrophs, mutant strains specifying enzymes with greatly diminished enzyme activities. Strains altered simultaneously at more than one step were also constructed by genetic recombination. By measuring the outputs of the pathway and the steady-state concentrations of intermediate pools, the fluxes in different parts of the pathway were calculated. This allowed the construction of flux/enzyme relationships, the slope of which is a measure of the sensitivity of a flux to the change in enzyme activity at that step. All fluxes were found to be considerably buffered for quite substantial decreases in the activities of all enzymes. Mass action plays an important part in this phenomenon, as do inhibition and repression. Because of the existence of expansion fluxes in growing systems, we find quantitatively different fluxes in different parts of the single pathway. For the same reason some enzyme modulations given decreased fluxes in one part and increased fluxes in another. The understanding of control in the pathway thus involves consideration of many mechanisms operating simultaneously and the estimation of changes in the whole system. The concept of a ‘rate-limiting step’ is found to be inadequate and is replaced by a quantitative measure, the Sensitivity Coefficient, which takes account of all the interactions. It is shown that control of the flux is shared among all the enzymes of the pathway. The results are discussed in terms of the theory of flux control.

ACC-OXIDASE IS THE RATE LIMITING STEP IN ETHYLENE BIOSYNTHESIS DURING POSTHARVEST STORAGE OF TOMATO

2012 ◽  
pp. 429-434 ◽  
Author(s):  
B. Van de Poel ◽  
I. Bulens ◽  
M.L.A.T.M. Hertog ◽  
B.M. Nicolaï ◽  
A.H. Geeraerd ◽  
...  
Keyword(s):  
Acc Oxidase ◽  
Ethylene Biosynthesis ◽  
Postharvest Storage ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting

scholarly journals Low Oxygen and Elevated Carbon Dioxide Atmospheres Inhibit Ethylene Biosynthesis in Preclimacteric and Climacteric Apple Fruit

1997 ◽  
Vol 122 (4) ◽  
pp. 542-546 ◽  
Author(s):  
James R. Gorny ◽  
Adel A. Kader
Keyword(s):  
Enzyme Activity ◽  
Mrna Level ◽  
Acc Oxidase ◽  
Acc Synthase ◽  
Transcript Abundance ◽  
Ethylene Biosynthesis ◽  
Apple Fruit ◽  
Low Oxygen ◽  
Rate Limiting Step

Autocatalytic C2H4 biosynthesis in preclimacteric apple fruit (Malus domestica Borkh. `Golden Delicious') was prevented by storage in atmospheres of 20% CO2-enriched air (17% O2 + 63% N2) or 0.25% O2 (balance N2). In preclimacteric fruit, both treatments inhibited C2H2 biosynthesis by suppressing expression of ACC synthase (ACC-S) at the mRNA level. ACC oxidase (ACC-O) mRNA abundance and in vitro enzyme activity also were impaired by these treatments. However, the conversion of ACC to C2H4 never became the rate limiting step in C2H4 biosynthesis. C2H4 biosynthesis also was effectively inhibited in climacteric apple fruit kept in air + 20% CO2 or 0.25% O2. Climacteric apples also exhibited suppressed expression of ACC-S at the mRNA level, while ACC-O transcript abundance, enzyme activity, and protein abundance were reduced only slightly. ACC-S is the key regulatory enzyme of C2H4 biosynthesis and is the major site at which elevated CO2 and reduced O2 atmospheres inhibit C2H4 biosynthesis, irrespective of fruit physiological maturity. Chemical names used: 1-aminocyclopropane-1-carboxcylic acid (ACC).

Reciprocal antagonistic regulation of E3 ligases controls ACC synthase stability and responses to stress

2021 ◽  
Vol 118 (34) ◽  
pp. e2011900118
Author(s):  
Han Yong Lee ◽  
Hye Lin Park ◽  
Chanung Park ◽  
Yi-Chun Chen ◽  
Gyeong Mee Yoon
Keyword(s):  
Stress Responses ◽  
Molecular Mechanisms ◽  
E3 Ligase ◽  
Acc Synthase ◽  
Ethylene Biosynthesis ◽  
Cellular Protein ◽  
Dependent Manner ◽  
E3 Ligases ◽  
Seven In Absentia ◽  
Rate Limiting

Ethylene influences plant growth, development, and stress responses via crosstalk with other phytohormones; however, the underlying molecular mechanisms are still unclear. Here, we describe a mechanistic link between the brassinosteroid (BR) and ethylene biosynthesis, which regulates cellular protein homeostasis and stress responses. We demonstrate that as a scaffold, 1-aminocyclopropane-1-carboxylic acid (ACC) synthases (ACS), a rate-limiting enzyme in ethylene biosynthesis, promote the interaction between Seven-in-Absentia of Arabidopsis (SINAT), a RING-domain containing E3 ligase involved in stress response, and ETHYLENE OVERPRODUCER 1 (ETO1) and ETO1-like (EOL) proteins, the E3 ligase adaptors that target a subset of ACS isoforms. Each E3 ligase promotes the degradation of the other, and this reciprocally antagonistic interaction affects the protein stability of ACS. Furthermore, 14–3-3, a phosphoprotein-binding protein, interacts with SINAT in a BR-dependent manner, thus activating reciprocal degradation. Disrupted reciprocal degradation between the E3 ligases compromises the survival of plants in carbon-deficient conditions. Our study reveals a mechanism by which plants respond to stress by modulating the homeostasis of ACS and its cognate E3 ligases.

scholarly journals Identification of BELL Transcription Factors Involved in Nodule Initiation and Development in the Legumes Pisum sativum and Medicago truncatula

Plants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1808
Author(s):  
Alexandra V. Dolgikh ◽  
Elizaveta S. Rudaya ◽  
Elena A. Dolgikh
Keyword(s):  
Transcription Factor ◽  
Transcription Factors ◽  
Pisum Sativum ◽  
Medicago Truncatula ◽  
Nodule Formation ◽  
La Protein ◽  
Potential Partner ◽  
Precise Analysis ◽  
Tale Homeodomain ◽  
Nodule Initiation

Single three-amino acid loop extension (TALE) homeodomain proteins, including the KNOTTED-like (KNOX) and BEL-like (BELL) families in plants, usually work as heterodimeric transcription factor complexes to regulate different developmental processes, often via effects on phytohormonal pathways. Nitrogen-fixing nodule formation in legumes is regulated by different families of homeodomain transcription factors. Whereas the role of KNOX transcription factors in the control of symbiosis was studied early, BELL transcription factors have received less attention. Here, we report the identification and expression analysis of BELL genes in the legume plants Medicago truncatula and Pisum sativum, which are involved in regulating symbiosis initiation and development. A more precise analysis was performed for the most significantly upregulated PsBELL1-2 gene in pea. We found that the PsBELL1-2 transcription factor could be a potential partner of PsKNOX9. In addition, we showed that PsBELL1-2 can interact with the PsDELLA1 (LA) protein-regulator of the gibberellin pathway, which has a previously demonstrated important role in symbiosis development.

scholarly journals Transient and intermediate carbocations in ruthenium tetroxide oxidation of saturated rings

2019 ◽  
Vol 15 ◽  
pp. 1552-1562
Author(s):  
Manuel Pedrón ◽  
Laura Legnani ◽  
Maria-Assunta Chiacchio ◽  
Pierluigi Caramella ◽  
Tomás Tejero ◽  
...  
Keyword(s):  
Topological Analysis ◽  
Ruthenium Tetroxide ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Iminium Ion ◽  
Single Transition ◽  
One Step ◽  
Two Stages ◽  
Rate Limiting ◽  
Mediated Oxidation

The ruthenium tetroxide-mediated oxidation of cyclopentane, tetrahydrofuran, tetrahydrothiophene andN-substituted pyrrolidines has been studied computationally by DFT and topological (analysis of the electron localization function, ELF) methods. In agreement with experimental observations and previous DFT calculations, the rate-limiting step of the reaction takes place through a highly asynchronous (3 + 2) concerted cycloaddition through a single transition structure (one kinetic step). The ELF analysis identifies the reaction as a typical one-step-two-stages process and corroborates the existence of a transient carbocation. In the case of pyrrolidines, the carbocation is completely stabilized as an energy minimum in the form of an iminium ion and the reaction takes place in two steps.

Solvolysis kinetics and mechanism of 3-methyl-1,3-thiazolidine-2,4-dione

1981 ◽  
Vol 46 (12) ◽  
pp. 3097-3103 ◽  
Author(s):  
Vladimír Macháček ◽  
Vojeslav Štěrba ◽  
Helena Zahradníčková
Keyword(s):  
Sodium Methoxide ◽  
Kinetics And Mechanism ◽  
Hydrolysis Kinetics ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Reaction Proceeds ◽  
One Step ◽  
Rate Limiting ◽  
Kinetics Of

The hydrolysis kinetics of 3-methyl-1,3-thiazolidine-2,4-dione have been studied in aqueous buffers and dilute NaOH solutions. The reaction proceeds via two base-catalyzed steps having different rates. In sodium methoxide solutions 3-methyl-1,3-thiazolidine-2,4-dione undergoes one-step methanolysis giving methyl thioglycolate anion as the final product. The rate-limiting step consists in decomposition of the anion CH3NCOSCH2COOCH3.

Sign in / Sign up

Export Citation Format

Share Document