Symbiosis-regulated expression of an acetyl-CoA acetyltransferase gene in the ectomycorrhizal fungus Laccaria bicolor

2006 ◽  
Vol 84 (9) ◽  
pp. 1405-1416 ◽  
Author(s):  
Shiv T. Hiremath ◽  
Sujata Balasubramanian ◽  
Jun Zheng ◽  
Gopi K. Podila
Keyword(s):  
Structural Changes ◽  
Plant Root ◽  
Ectomycorrhizal Fungus ◽  
Malate Synthase ◽  
Laccaria Bicolor ◽  
Symbiotic Association ◽  
Acetyl Coa ◽  
Ectomycorrhizal Symbiosis ◽  
Coordinated Expression ◽  
Lipid Metabolism Genes

The ectomycorrhiza is a symbiotic organ generated from the intricate association of fungal hyphae and plant root. The establishment of the ectomycorrhiza is a coordinated process of cross-talk between plant and fungus, followed by metabolic, developmental, and structural changes in the fungus, resulting in its growth toward the root. The initial stages of the symbiotic association are significant, since the direction of the association is determined by the gene expression level shifts that occur at this time. We have isolated a Laccaria bicolor (Maire) Orton cDNA clone corresponding to acetyl-CoA acetyltransferase (Lb-AAT), which is expressed during interaction with red pine roots and is symbiosis regulated. Acetyl-CoA acetyltransferase (EC 2.3.1.9) is an enzyme of the β-oxidation pathway that degrades long-chain fatty acids to acetyl-CoA. Expression of Lb-AAT is regulated by plant presence, by glucose, and by the presence of acetate or oleate in the medium. It is proposed that the role of Lb-AAT in the symbiosis is generation of two carbon compounds from stored lipids and generation of acetoacetyl-CoA in early interaction facilitating net growth from existing cell material. These results coupled with recent microarray analysis that revealed coordinated expression of malate synthase and other lipid metabolism genes along with Lb-AAT, suggest that this role for Lb-AAT could be an important part of preinfection process in ectomycorrhizal symbiosis and in the transfer and utilization of the carbon in the fungus.

scholarly journals Metabolomics and transcriptomics to decipher molecular mechanisms underlying ectomycorrhizal root colonization of an oak tree

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. Sebastiana ◽  
A. Gargallo-Garriga ◽  
J. Sardans ◽  
M. Pérez-Trujillo ◽  
F. Monteiro ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Positive Impact ◽  
Ectomycorrhizal Fungus ◽  
Cork Oak ◽  
Mycorrhizal Symbiosis ◽  
Gamma Aminobutyric Acid ◽  
Ectomycorrhizal Symbiosis ◽  
Ectomycorrhizal Roots ◽  
Oak Tree ◽  
Mycorrhizal Roots

AbstractMycorrhizas are known to have a positive impact on plant growth and ability to resist major biotic and abiotic stresses. However, the metabolic alterations underlying mycorrhizal symbiosis are still understudied. By using metabolomics and transcriptomics approaches, cork oak roots colonized by the ectomycorrhizal fungus Pisolithus tinctorius were compared with non-colonized roots. Results show that compounds putatively corresponding to carbohydrates, organic acids, tannins, long-chain fatty acids and monoacylglycerols, were depleted in ectomycorrhizal cork oak colonized roots. Conversely, non-proteogenic amino acids, such as gamma-aminobutyric acid (GABA), and several putative defense-related compounds, including oxylipin-family compounds, terpenoids and B6 vitamers were induced in mycorrhizal roots. Transcriptomic analysis suggests the involvement of GABA in ectomycorrhizal symbiosis through increased synthesis and inhibition of degradation in mycorrhizal roots. Results from this global metabolomics analysis suggest decreases in root metabolites which are common components of exudates, and in compounds related to root external protective layers which could facilitate plant-fungal contact and enhance symbiosis. Root metabolic pathways involved in defense against stress were induced in ectomycorrhizal roots that could be involved in a plant mechanism to avoid uncontrolled growth of the fungal symbiont in the root apoplast. Several of the identified symbiosis-specific metabolites, such as GABA, may help to understand how ectomycorrhizal fungi such as P. tinctorius benefit their host plants.

scholarly journals The Apparent Malate Synthase Activity of Rhodobacter sphaeroides Is Due to Two Paralogous Enzymes, (3S)-Malyl-Coenzyme A (CoA)/β-Methylmalyl-CoA Lyase and (3S)- Malyl-CoA Thioesterase

2010 ◽  
Vol 192 (5) ◽  
pp. 1249-1258 ◽  
Author(s):  
Tobias J. Erb ◽  
Lena Frerichs-Revermann ◽  
Georg Fuchs ◽  
Birgit E. Alber
Keyword(s):  
Rhodobacter Sphaeroides ◽  
Coenzyme A ◽  
Glyoxylate Cycle ◽  
Condensation Reaction ◽  
Malate Synthase ◽  
Acetyl Coa ◽  
Acetyl Coenzyme A ◽  
Claisen Condensation ◽  
Enzyme Functions ◽  
The Glyoxylate Cycle

ABSTRACT Assimilation of acetyl coenzyme A (acetyl-CoA) is an essential process in many bacteria that proceeds via the glyoxylate cycle or the ethylmalonyl-CoA pathway. In both assimilation strategies, one of the final products is malate that is formed by the condensation of acetyl-CoA with glyoxylate. In the glyoxylate cycle this reaction is catalyzed by malate synthase, whereas in the ethylmalonyl-CoA pathway the reaction is separated into two proteins: malyl-CoA lyase, a well-known enzyme catalyzing the Claisen condensation of acetyl-CoA with glyoxylate and yielding malyl-CoA, and an unidentified malyl-CoA thioesterase that hydrolyzes malyl-CoA into malate and CoA. In this study the roles of Mcl1 and Mcl2, two malyl-CoA lyase homologs in Rhodobacter sphaeroides, were investigated by gene inactivation and biochemical studies. Mcl1 is a true (3S)-malyl-CoA lyase operating in the ethylmalonyl-CoA pathway. Notably, Mcl1 is a promiscuous enzyme and catalyzes not only the condensation of acetyl-CoA and glyoxylate but also the cleavage of β-methylmalyl-CoA into glyoxylate and propionyl-CoA during acetyl-CoA assimilation. In contrast, Mcl2 was shown to be the sought (3S)-malyl-CoA thioesterase in the ethylmalonyl-CoA pathway, which specifically hydrolyzes (3S)-malyl-CoA but does not use β-methylmalyl-CoA or catalyze a lyase or condensation reaction. The identification of Mcl2 as thioesterase extends the enzyme functions of malyl-CoA lyase homologs that have been known only as “Claisen condensation” enzymes so far. Mcl1 and Mcl2 are both related to malate synthase, an enzyme which catalyzes both a Claisen condensation and thioester hydrolysis reaction.

scholarly journals Ligand binding on to maize (Zea mays) malate synthase: a structural study

1994 ◽  
Vol 303 (2) ◽  
pp. 413-421 ◽  
Author(s):  
S Beeckmans ◽  
A S Khan ◽  
L Kanarek ◽  
E Van Driessche
Keyword(s):  
Zea Mays ◽  
Ligand Binding ◽  
Conformational Change ◽  
Limited Proteolysis ◽  
Enzymic Activity ◽  
Malate Synthase ◽  
Acetyl Coa ◽  
Original Activity ◽  
Kinetic Measurements ◽  
Michaelis Constants

A kinetic and ligand binding study on maize (Zea mays) malate synthase is presented. It is concluded from kinetic measurements that the enzyme proceeds through a ternary-complex mechanism. Michaelis constants (Km,glyoxylate and Km,acetyl-CoA) were determined to be 104 microM and 20 microM respectively. C.d. measurements in the near u.v.-region indicate that a conformational change is induced in the enzyme by its substrate, glyoxylate. From these studies we are able to calculate the affinity for the substrate (Kd,glyoxylate) as 100 microM. A number of inhibitors apparently trigger the same conformational change in the enzyme, i.e. pyruvate, glycollate and fluoroacetate. Another series of inhibitors bearing more bulky groups and/or an extra carboxylic acid also induce a conformational change, which is, however, clearly different from the former one. Limited proteolysis with trypsin results in cleavage of malate synthase into two fragments of respectively 45 and 19 kDa. Even when no more intact malate synthase chains are present, the final enzymic activity still amounts to 30% of the original activity. If trypsinolysis is performed in the presence of acetyl-CoA, the cleavage reaction is appreciably slowed down. The dissociation constant for acetyl-CoA (Kd,acetyl-CoA) was calculated to be 14.8 microM when the glyoxylate subsite is fully occupied by pyruvate and 950 microM (= 50 x Km) when the second subsite is empty. It is concluded that malate synthase follows a compulsory-order mechanism, glyoxylate being the first-binding substrate. Glyoxylate triggers a conformational change in the enzyme and, as a consequence, the correctly shaped binding site for acetyl-CoA is created. Demetallization of malate synthase has no effect on the c.d. spectrum in the near u.v.-region. Moreover, glyoxylate induces the same spectral change in the absence of Mg2+ as in its presence. Nevertheless, malate synthase shows no activity in the absence of the cation. We conclude that Mg2+ is essential for catalysis, rather than for the structure of the enzyme's catalytic site.

scholarly journals Pseudomonas aeruginosa Twitching Motility-Mediated Chemotaxis towards Phospholipids and Fatty Acids: Specificity and Metabolic Requirements

2008 ◽  
Vol 190 (11) ◽  
pp. 4038-4049 ◽  
Author(s):  
Rhea M. Miller ◽  
Andrew P. Tomaras ◽  
Adam P. Barker ◽  
Dennis R. Voelker ◽  
Edward D. Chan ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Alternative Energy ◽  
Isocitrate Lyase ◽  
Malate Synthase ◽  
Glyoxylate Shunt ◽  
Twitching Motility ◽  
Long Chain Fatty Acid ◽  
Type Iv ◽  
Energy Taxis ◽  
Lipid Metabolism Genes

ABSTRACT Pseudomonas aeruginosa demonstrates type IV pilus-mediated directional twitching motility up a gradient of phosphatidylethanolamine (PE). Only one of four extracellular phospholipases C of P. aeruginosa (i.e., PlcB), while not required for twitching motility per se, is required for twitching-mediated migration up a gradient of PE or phosphatidylcholine. Whether other lipid metabolism genes are associated with this behavior was assessed by analysis of transcription during twitching up a PE gradient in comparison to transcription during twitching in the absence of any externally applied phospholipid. Data support the hypothesis that PE is further degraded and that the long-chain fatty acid (LCFA) moieties of PE are completely metabolized via β-oxidation and the glyoxylate shunt. It was discovered that P. aeruginosa exhibits twitching-mediated chemotaxis toward unsaturated LCFAs (e.g., oleic acid), but not saturated LCFAs (e.g., stearic acid) of corresponding lengths. Analysis of mutants that are deficient in glyoxylate shunt enzymes, specifically isocitrate lyase (ΔaceA) and malate synthase (ΔaceB), suggested that the complete metabolism of LCFAs through this pathway was required for the migration of P. aeruginosa up a gradient of PE or unsaturated LCFAs. At this point, our data suggested that this process should be classified as energy taxis. However, further evaluation of the ability of the ΔaceA and ΔaceB mutants to migrate up a gradient of PE or unsaturated LCFAs in the presence of an alternative energy source clearly indicated that metabolism of LCFAs for energy is not required for chemotaxis toward these compounds.

Survival in the soil of the ectomycorrhizal fungus Laccaria bicolor and the effects of a mycorrhiza helper Pseudomonas fluorescens

2001 ◽  
Vol 33 (12-13) ◽  
pp. 1683-1694 ◽  
Author(s):  
C Brulé ◽  
P Frey-Klett ◽  
J.C Pierrat ◽  
S Courrier ◽  
F Gérard ◽  
...  
Keyword(s):  
Pseudomonas Fluorescens ◽  
Ectomycorrhizal Fungus ◽  
Laccaria Bicolor
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