Recombinant Agrostis stolonifera NAD (P)H-quinone oxidoreductase subunit 3, chloroplastic

What is the basic biochemical profile of Agrostis stolonifera NAD(P)H-quinone oxidoreductase subunit 3?

Agrostis stolonifera (Creeping bentgrass) NAD(P)H-quinone oxidoreductase subunit 3 is a chloroplastic protein with UniProt accession number A1EA13. The recombinant form is typically stored in a Tris-based buffer with 50% glycerol, optimized for protein stability. The amino acid sequence includes functional domains characteristic of NAD(P)H dehydrogenase activity . The protein participates in electron transfer reactions within the chloroplast, contributing to various cellular metabolic processes.

For optimal protein stability during experimental procedures, the following storage conditions are recommended:

How does the NAD(P)H-quinone oxidoreductase function in Agrostis stolonifera compared to other plant species?

NAD(P)H-quinone oxidoreductase in A. stolonifera functions similarly to homologous proteins in other plant species, but with distinct regulatory patterns likely shaped by the evolutionary history of creeping bentgrass. Particularly noteworthy is its role in superoxide scavenging and quinone detoxification pathways.

The catalytic mechanism follows a ping-pong reaction pattern, where:

• NAD(P)H binds to the enzyme, reducing the flavin cofactor

• NAD(P)+ is released from the active site

• Quinone substrate binds to the vacated position

• Direct hydride transfer occurs from the reduced flavin to the quinone substrate

Comparative studies with mammalian NAD(P)H:quinone oxidoreductases show that while the core catalytic mechanism is preserved, substrate specificity and regulatory controls differ substantially between plant and animal systems .

How is NAD(P)H-quinone oxidoreductase expression affected by environmental stressors in Agrostis stolonifera?

Transcriptomic analysis reveals that NAD(P)H-quinone oxidoreductase gene expression in A. stolonifera is significantly modulated during environmental stress conditions, particularly drought and heat. RNA-seq studies have demonstrated that genes encoding electron transfer proteins, including a probable electron transfer flavoprotein-quinone oxidoreductase, show upregulation (3.2-fold increase) under drought stress conditions .

In the broader stress response network, this upregulation correlates with:

• Enhanced oxylipin biosynthetic processes (the most enriched GO term in commonly up-regulated transcripts)

• Increased proline biosynthesis

• Modified nitrogen compound metabolic processes (GO:0006807; FDR<0.0001)

These changes suggest that NAD(P)H-quinone oxidoreductase plays a crucial role in cellular redox maintenance during stress, potentially contributing to ROS scavenging mechanisms that protect photosynthetic machinery .

What methodologies are most effective for quantifying NAD(P)H-quinone oxidoreductase expression levels in Agrostis stolonifera?

For reliable quantification of NAD(P)H-quinone oxidoreductase expression in A. stolonifera, researchers should employ a multi-method approach:

• RT-qPCR analysis: Enables precise quantification of transcript abundance. For optimal results, use reference genes such as AsAct (actin) for normalization. Cycle threshold (Cq) values between 24-28 typically indicate reliable expression levels .

• RNA-seq analysis: Provides comprehensive transcriptome profiling with over 18x coverage of the estimated transcriptome size (~417Mbp) of A. stolonifera. This approach allows detection of differentially expressed genes (DEGs) using thresholds of FDR <0.001 and |log2 of fold change (FC)| >1 .

• Protein quantification: Western blotting with antibodies specific to the NAD(P)H-quinone oxidoreductase or activity assays using purified recombinant protein can complement transcriptional analysis.

When conducting RT-qPCR analysis, note that some genes (like the monooxygenase-like gene in A. stolonifera) may show detectable amplification only after 32 reaction cycles, making them unsuitable for relative gene expression analysis .

What are the optimal conditions for expressing and purifying recombinant Agrostis stolonifera NAD(P)H-quinone oxidoreductase?

Based on established protocols for similar NAD(P)H-quinone oxidoreductases, the following optimized procedure is recommended:

• Expression system: Heterologous expression in Escherichia coli, using vectors with strong inducible promoters (e.g., T7 promoter systems).

• Purification protocol:

  • Initial purification via affinity chromatography (if using tagged constructs)

  • Further purification using ion exchange chromatography

  • Final polishing step with size exclusion chromatography

• Protein concentration: Aim for 10-15 mg/ml (≈500 μM) in 25 mM Tris-HCl, pH 8.0 buffer with 5 μM FAD .

• Crystallization conditions: For structural studies, employ hanging drop vapor diffusion method using:

  • Reservoir solution: 30% PEG 3350, 200 mM sodium-acetate, 100 mM sodium-tricine at pH 8.5, and 12-24 μM FAD

  • Equilibration temperature: 25°C

• Storage recommendations: Store purified protein at -20°C with 50% glycerol to maintain stability. For working aliquots, store at 4°C for up to one week to avoid repeated freeze-thaw cycles .

How can researchers effectively measure NAD(P)H-quinone oxidoreductase enzymatic activity?

To accurately measure NAD(P)H-quinone oxidoreductase activity, researchers should employ these methodological approaches:

• Spectrophotometric assays:

  • Monitor NADH oxidation at 340 nm using quinone substrates

  • For superoxide scavenging activity, measure the rate of NADH oxidation using xanthine/xanthine oxidase as a source of superoxide

• Kinetic parameter determination:

  • Determine kinetic parameters (Km, kcat) using various concentrations of NAD(P)H and quinone substrates

  • Conduct assays at physiologically relevant pH (typically pH 7.4-7.8)

• Inhibitor studies:

  • Use mechanism-based inhibitors such as 5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]indole-4,7-dione (ES936) to confirm specificity of the measured activity

• Superoxide scavenging assessment:

  • Measure inhibition of dihydroethidium oxidation

  • Assess pyrogallol auto-oxidation

  • Employ electron spin resonance to detect elimination of superoxide adduct signals

When conducting activity assays, it's critical to account for the ping-pong reaction mechanism where NAD(P)+ leaves the catalytic site before substrate binding occurs .

How does Agrostis stolonifera NAD(P)H-quinone oxidoreductase compare structurally and functionally to homologs in other species?

Structural and functional comparison of A. stolonifera NAD(P)H-quinone oxidoreductase with mammalian homologs reveals both conserved features and species-specific adaptations:

Evolutionary analysis suggests that while the core catalytic function is preserved across species, fine specificity features have evolved to match the physiological needs of each organism.

What evidence exists for lateral gene transfer in the evolution of NAD(P)H-quinone oxidoreductase genes in Agrostis stolonifera?

Comprehensive genomic analysis provides compelling evidence for lateral gene transfer (LGT) in the evolution of certain oxidoreductase genes in A. stolonifera:

• Phylogenetic analysis:

  • Close relationships between A. stolonifera genes and corresponding genes in fungal endophyte species of the Epichloë genus

  • Sequence alignment shows that the DNA sequence identity between AsBGNL and the corresponding E. amarillans gene was 93%, with an alignment length of 1153 bases

• Taxonomic distribution:

  • Presence of oxidoreductase-like genes confined to specific genera (Agrostis, Deyeuxia) but absent in other species belonging to the clade 1 of the Poeae tribe

  • In silico screening confirmed presence in Agrostis and Deyeuxia species but absence in other tested plant taxa

• Expression analysis:

  • RT-qPCR data demonstrated that transferred genes are functionally expressed in plant tissues

  • Ubiquitous expression in young seedlings, including root tissues where Epichloë endophytes are not present

This evidence suggests that functional oxidoreductase genes in A. stolonifera originated through LGT from fungal endophytes of the Epichloë lineage, contributing to the metabolic capabilities of the plant.

How can Agrostis stolonifera NAD(P)H-quinone oxidoreductase be utilized in stress tolerance engineering?

Exploiting NAD(P)H-quinone oxidoreductase for enhancing stress tolerance in plants represents an advanced research frontier with several promising approaches:

• Transgenic overexpression strategies:

  • Enhance ROS scavenging capacity by overexpressing NAD(P)H-quinone oxidoreductase genes

  • Target expression to chloroplasts to protect photosynthetic machinery during stress

  • Combine with other stress-responsive genes for synergistic protection

• Regulatory network engineering:

  • Modify transcriptional regulators that control NAD(P)H-quinone oxidoreductase expression

  • Target common regulatory elements affecting both heat and drought stress response

  • Focus on the 670 commonly up-regulated genes identified in stress transcriptome studies

• Metabolic pathway enhancement:

  • Strengthen oxylipin biosynthetic pathways that are associated with stress response

  • Target proline biosynthetic processes that show coordinated regulation with oxidoreductase genes

  • Modify thiamine metabolic processes and calcium sensing that show downregulation during stress

These approaches can be evaluated using high-throughput phenotyping platforms to assess stress tolerance parameters including photosynthetic efficiency, ROS accumulation, and survival rates under controlled stress conditions.

What role might NAD(P)H-quinone oxidoreductase play in advanced bioremediation applications using Agrostis stolonifera?

NAD(P)H-quinone oxidoreductase in A. stolonifera holds significant potential for bioremediation applications, particularly for sites contaminated with heavy metals and organic pollutants:

• Heavy metal detoxification:

  • NAD(P)H-quinone oxidoreductase may contribute to redox homeostasis in plants exposed to heavy metals

  • A. stolonifera has demonstrated potential for restoring mine sites involving heavy metals

  • Enhanced oxidoreductase activity could improve electron transfer processes needed for metal detoxification

• Organic pollutant degradation:

  • Quinone reductases can participate in the reduction of various environmental contaminants

  • Modified expression could enhance degradation of quinone-containing xenobiotics

  • Coupling with other detoxification enzymes could create more effective remediation systems

• Water treatment applications:

  • A. stolonifera has been investigated for water treatment applications

  • NAD(P)H-quinone oxidoreductase activity could contribute to degradation of contaminants in constructed wetlands

  • Engineering enhanced expression could improve treatment efficiency

Research in this direction would benefit from controlled field studies comparing wild-type and engineered A. stolonifera variants for remediation efficiency across different contaminant profiles.

What are the current methodological limitations in studying recombinant Agrostis stolonifera NAD(P)H-quinone oxidoreductase?

Researchers face several methodological challenges when working with recombinant A. stolonifera NAD(P)H-quinone oxidoreductase:

• Protein stability issues:

  • Maintaining enzyme stability during purification and storage

  • Preserving native conformation and activity in vitro

  • Preventing oxidative damage to the protein during experimental manipulation

• Functional characterization barriers:

  • Limited availability of plant-specific substrates for activity assays

  • Challenges in reconstituting physiologically relevant conditions

  • Difficulties in distinguishing between different isoforms

• Structural analysis constraints:

  • Challenges in obtaining high-resolution crystal structures

  • Conformational changes during catalysis complicate structural studies

  • Limited structural data for plant-specific forms compared to mammalian homologs

To overcome these limitations, researchers should consider:

• Employing advanced protein stabilization methods during purification

• Developing plant-specific activity assays with relevant quinone substrates

• Utilizing cryo-electron microscopy for structural studies of difficult-to-crystallize variants

What emerging technologies and approaches might advance research on NAD(P)H-quinone oxidoreductase function in Agrostis stolonifera?

Several cutting-edge technologies show promise for advancing our understanding of NAD(P)H-quinone oxidoreductase function:

• CRISPR/Cas9 genome editing:

  • Precise modification of NAD(P)H-quinone oxidoreductase genes in A. stolonifera

  • Creation of knockout or reporter lines to study function in vivo

  • Introduction of specific mutations to test structure-function hypotheses

• Single-cell transcriptomics:

  • Analysis of cell-type specific expression patterns

  • Identification of regulatory networks at cellular resolution

  • Mapping stress responses with unprecedented precision

• Protein engineering approaches:

  • Directed evolution to improve catalytic efficiency or substrate specificity

  • Rational design of enhanced oxidoreductases for specific applications

  • Development of fusion proteins for novel functions or localization

• Advanced imaging technologies:

  • Live-cell imaging of enzyme activity using fluorescent sensors

  • Super-resolution microscopy to determine subcellular localization

  • FRET-based approaches to study protein-protein interactions

• Systems biology integration:

  • Multi-omics analysis combining transcriptomics, proteomics, and metabolomics

  • Mathematical modeling of redox networks involving NAD(P)H-quinone oxidoreductase

  • Prediction of emergent properties in stress response networks

These technologies, particularly when used in combination, have the potential to revolutionize our understanding of NAD(P)H-quinone oxidoreductase function in plant systems and open new avenues for biotechnological applications.