Recombinant Spodoptera frugiperda Cytochrome c oxidase subunit 3 (COIII)
Description
Introduction to Recombinant Spodoptera frugiperda Cytochrome c oxidase subunit 3 (COIII)
Cytochrome c oxidase subunit 3 (COIII) functions as a crucial component of the mitochondrial electron transport chain, specifically within complex IV (cytochrome c oxidase). This complex serves as the terminal electron acceptor in cellular respiration, catalyzing the reduction of molecular oxygen to water while simultaneously generating a proton gradient across the inner mitochondrial membrane that drives ATP synthesis. In Spodoptera frugiperda, commonly known as the fall armyworm, COIII is encoded by the mitochondrial genome and constitutes an integral part of the cellular energy production machinery .
Spodoptera frugiperda has emerged as a species of significant concern in recent years due to its rapid global spread from its native Americas. First reported in West Africa in 2016, this invasive pest has subsequently expanded its range across Africa and into Asia, causing substantial agricultural damage, particularly to corn crops . The species has been confirmed in over 70 countries across multiple continents, highlighting its remarkable invasive capacity and adaptation potential . Given its economic importance, understanding the fundamental biology of this pest, including its mitochondrial proteins such as COIII, has become increasingly relevant for both basic science and applied research.
Recombinant Spodoptera frugiperda COIII refers to the artificially produced version of this protein, typically expressed in bacterial systems like Escherichia coli for research and commercial applications. The recombinant form often includes modifications such as histidine tags to facilitate purification and downstream experimental applications .
Expression and Purification of Recombinant Spodoptera frugiperda COIII
The production of recombinant Spodoptera frugiperda COIII primarily utilizes bacterial expression systems, with E. coli being the predominant host organism. This approach offers advantages in terms of efficiency, cost-effectiveness, and scalability for protein production . The expression process typically involves cloning the COIII gene into a suitable expression vector, transformation into competent E. coli cells, and induction of protein expression under optimized conditions.
Following expression, the recombinant protein undergoes a series of purification steps to isolate it from bacterial cellular components. The N-terminal histidine tag facilitates purification through immobilized metal affinity chromatography (IMAC), where the tagged protein selectively binds to metal ions (typically nickel or cobalt) immobilized on a solid support. After purification, the protein preparation typically achieves greater than 90% purity as determined by SDS-PAGE analysis .
The purified protein is commonly provided in lyophilized form for improved stability during shipping and storage. For experimental use, the protein requires reconstitution in appropriate buffers according to specific protocols designed to maintain protein integrity and activity. The reconstituted protein is typically stored in Tris/PBS-based buffer containing 6% trehalose at pH 8.0, which helps maintain protein stability during storage .
Applications and Research Significance of Recombinant Spodoptera frugiperda COIII
Recombinant Spodoptera frugiperda COIII serves as a valuable tool for various research applications, particularly in fields related to insect physiology, mitochondrial function, and host-pathogen interactions. The availability of purified recombinant protein facilitates several research avenues:
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Structural and Functional Studies: Purified recombinant COIII enables detailed structural analysis and functional characterization of this component of the cytochrome c oxidase complex. Understanding the structure-function relationship of this protein could provide insights into the specific mechanisms of mitochondrial respiration in Spodoptera frugiperda.
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Comparative Mitochondrial Research: The protein allows for comparative studies of mitochondrial respiratory components across different insect species, potentially revealing evolutionary adaptations and species-specific features. Such comparisons could be particularly valuable given the global spread of Spodoptera frugiperda and its adaptation to diverse environments.
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Host-Pathogen Interaction Studies: Given the observed changes in COIII expression during viral infection, the recombinant protein may facilitate investigations into how mitochondrial function is modulated during pathogenic challenges . This research avenue could contribute to understanding the complex interplay between cellular metabolism and immune response in insects.
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Biomarker Development: As a mitochondrial protein with potential regulatory responses to environmental and pathogenic stressors, COIII could serve as a biomarker for various physiological states or stresses in Spodoptera frugiperda. Such biomarkers could be valuable for monitoring population health and stress responses in field studies.
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Target Identification for Pest Control: Understanding the structure and function of essential mitochondrial proteins like COIII may contribute to the identification of novel targets for species-specific pest control strategies. Given the global significance of Spodoptera frugiperda as an agricultural pest, such approaches could have substantial economic impact.
The global spread of Spodoptera frugiperda has been documented through molecular diagnostic approaches, including analysis of mitochondrial DNA markers . While these studies have primarily utilized the cytochrome c oxidase subunit I (COI) gene as a molecular marker rather than COIII, they highlight the importance of mitochondrial genes in species identification and population genetics of this invasive pest.
Product Specs
Note: We prioritize shipping the format currently in stock. However, if you have specific format requirements, please indicate them when placing your order. We will accommodate your request whenever possible.
Note: All our proteins are shipped with standard blue ice packs. If you require dry ice shipping, please inform us in advance. Additional fees will apply.
Generally, the shelf life of liquid form is 6 months at -20°C/-80°C. The shelf life of lyophilized form is 12 months at -20°C/-80°C.
Target Background
Q&A
What is the role of Cytochrome c oxidase subunit 3 (COIII) in Spodoptera frugiperda?
COIII is one of the three core subunits of the aa3-type cytochrome c oxidase in the mitochondrial respiratory chain. Unlike other subunits, COIII does not contain any redox centers but plays an important structural role. Contrary to earlier assumptions, research has revealed that COIII is not an essential element of the proton pump mechanism, though it has significance in the enzyme biosynthesis . In S. frugiperda, COIII sequences vary between host strains, making it valuable for molecular identification alongside other mitochondrial markers like COI and Cyt b .
How do COIII sequences differ between corn-strain and rice-strain populations of S. frugiperda?
The corn strain (SfC) and rice strain (SfR) of S. frugiperda show distinct haplotype patterns in their COIII sequences. Studies detecting maternal lineages in invasive populations have found that combining mtDNA COI/Cyt b haplotypes with COIII haplotypes enables identification of unique maternal lineages, particularly in corn-preferred FAW samples . The molecular differentiation between these strains (which have been regarded both as host strains and as closely related sister species) is approximately 1.9% at the genomic level , with COIII contributing to this differentiation pattern.
What are the advantages of using COIII as a molecular marker compared to other mitochondrial genes?
While COI is the most commonly used marker for FAW strain identification, COIII offers several complementary advantages:
| Mitochondrial Marker | Advantages | Limitations | Best Application |
|---|---|---|---|
| COI | Industry standard, extensive reference database | May not resolve all maternal lineages | Primary identification, DNA barcoding |
| Cyt b | Highly conserved, good for phylogenetics | Limited strain-specific polymorphisms | Evolutionary studies, deep phylogeny |
| COIII | Can identify unique maternal lineages when combined with other markers | Less reference data than COI | Complementary analysis, maternal lineage tracing |
Research in Uganda demonstrated that COIII sequences, when analyzed in combination with COI/Cyt b haplotypes, revealed previously unidentified maternal lineages in invasive populations , suggesting that at least three maternal lineages were involved in African incursions of S. frugiperda.
What are the optimal protocols for cloning and expressing recombinant S. frugiperda COIII?
Recombinant expression of membrane proteins like COIII presents significant challenges. Based on experimental approaches with similar proteins, the following methodology is recommended:
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Gene optimization and vector selection: Optimize the COIII gene sequence for the expression system (typically E. coli or insect cell lines) and clone into vectors containing appropriate fusion tags (His-tag, GST) to facilitate purification.
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Expression system selection: The S. frugiperda cell line (SF9) offers advantages for expression of insect mitochondrial proteins, as it provides the appropriate cellular machinery for post-translational modifications . Alternatively, bacterial systems with specialized membranes can be used.
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Solubilization strategy: After expression, membrane proteins require careful solubilization using mild detergents (n-dodecyl β-D-maltoside or digitonin) that maintain protein structure and function.
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Purification approach: Multi-step purification typically involving affinity chromatography followed by size exclusion chromatography is recommended to obtain pure, functional protein.
The success of recombinant COIII expression can be assessed through Western blotting and activity assays similar to those used in UGT enzyme studies with S. frugiperda .
How can site-directed mutagenesis of COIII advance understanding of its structural properties?
Site-directed mutagenesis represents a powerful approach for investigating the structural and functional properties of COIII in S. frugiperda. Based on studies of COIII in other systems, research has shown that:
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Targeting conserved residues: Invariant carboxylic acids (such as E98 and D259) can be modified to study their role in protein structure and function .
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Mutagenesis workflow:
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Identify conserved amino acids through sequence alignment
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Design mutagenic primers to introduce specific changes
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Perform PCR-based mutagenesis
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Verify mutations by sequencing
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Express and characterize mutant proteins
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Functional assessment: Spectroscopy and activity measurements can be used to determine if structurally normal enzymes are formed in the presence of the mutagenized COIII .
Studies on other species have revealed that mutations in conserved COIII residues do not abolish electron transfer activity, suggesting that COIII plays primarily a structural role rather than a catalytic one in the cytochrome c oxidase complex .
What experimental design is most appropriate for analyzing functional differences between strain-specific COIII variants?
For comparative analysis of strain-specific COIII variants, a multi-faceted experimental design is recommended:
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Reciprocal transplant approach: Similar to studies examining host plant adaptation in S. frugiperda , a reciprocal design can be employed to examine how COIII variants perform under different environmental conditions.
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Principal component-based analytical framework: Multi-trait selection indices based on principal component analysis can help identify significant differences between variants .
| Experimental Element | Control Measures | Variables to Monitor | Statistical Analysis |
|---|---|---|---|
| Expression system | Standardized vectors and cell lines | Expression levels, protein folding | ANOVA |
| Functional assays | Reference substrates | Electron transfer rates, oxygen consumption | Multiple regression |
| Structural analysis | Standardized purification methods | Protein stability, conformation | Principal component analysis |
A true experimental design with randomized treatments is preferable, but when this is not possible due to inherent strain differences, a quasi-experimental design may be employed . This approach should include between-subjects or within-subjects assignment depending on the specific research question .
How can COIII molecular data contribute to tracking global invasion patterns of S. frugiperda?
COIII sequence data, particularly when combined with other molecular markers, provides valuable insights into invasion pathways of S. frugiperda:
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Maternal lineage tracing: Since mitochondrial DNA is maternally inherited, COIII haplotypes can trace maternal lineages across invasion fronts. Research in Uganda identified at least three maternal lineages involved in African invasions .
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Population genomic signatures: Integrating COIII with nuclear markers (like Triose Phosphate Isomerase) allows for more comprehensive assessment of population structure during invasion events .
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Monitoring methodology: For effective invasion monitoring, a combination of field collection, molecular identification, and geospatial analysis is recommended.
| Region | Dominant COIII Haplotypes | Associated Strain | Initial Detection | Spread Pattern |
|---|---|---|---|---|
| Africa (Western) | Matches those in Nigeria | Primarily corn-strain | 2016 | Rapid eastward expansion |
| Africa (Eastern) | New maternal lineage identified in Uganda | Corn-strain | Following western introduction | Continued agricultural impact |
| Asia | Multiple haplotypes detected | Both corn and rice strains | Recent introductions | Under investigation |
| Oceania (PNG) | Confirmed molecular presence | Strain status undetermined | Recently confirmed | Agricultural monitoring ongoing |
The invasive populations in Africa were first reported in Nigeria and São Tomé and Principe in 2016, with subsequent confirmation in Uganda through molecular characterization including COIII sequencing .
What PCR-RFLP protocols can be developed for strain identification using COIII?
PCR-RFLP (Restriction Fragment Length Polymorphism) methods offer cost-effective approaches for strain identification:
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Protocol development: Based on related studies with COI, a PCR-RFLP method can be developed that does not require purification of mitochondrial DNA or the use of radioactive isotopes .
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Primer design for COIII amplification:
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Forward primer targeting conserved regions (e.g., positions complementary to 1,473 of reference sequence)
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Reverse primer (e.g., positions complementary to 2,166 of reference sequence)
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Amplicon size: approximately 693 bp
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Restriction enzyme selection: Identify restriction enzymes that cut specifically at sites present in one strain but not the other. For COI, MspI has been used to differentiate corn and rice strains , and similar strain-specific cut sites could be identified in COIII.
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Validation requirements: The method should be validated against known strain samples and compared with results from COI and TPI gene analyses to confirm accuracy.
This approach requires only a few nanograms of total DNA to yield clear and accurate strain identification of individual insects, making it particularly valuable for field applications .
What are the key challenges in expressing functional recombinant COIII protein?
Several significant challenges must be addressed when working with recombinant COIII:
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Membrane protein solubility: As a hydrophobic membrane protein, COIII is difficult to solubilize while maintaining its native structure. This often requires optimization of detergent types and concentrations.
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Post-translational modifications: If S. frugiperda COIII requires specific post-translational modifications, expression systems must be chosen accordingly. Insect cell lines may provide advantages over bacterial systems.
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Protein-protein interactions: COIII functions as part of a multi-subunit complex. Expressing it in isolation may affect its folding and stability.
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Functional assessment: Unlike enzymes with readily measurable catalytic activities, assessing the function of structural membrane proteins like COIII requires specialized techniques such as circular dichroism spectroscopy or structural studies.
Future studies should consider co-expression with other cytochrome c oxidase subunits to enhance stability and functional characterization.
How might COIII genetic variation contribute to adaptation of S. frugiperda to different environments?
The COIII gene may play a role in metabolic adaptation of S. frugiperda to different host plants and environments:
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Strain-specific adaptation: Differences in COIII sequences between corn and rice strains may affect mitochondrial function and energy metabolism, potentially contributing to host plant adaptation .
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Selection pressure hypothesis: Since mitochondrial genotypes are among the main genetic variations between the strains, researchers have proposed that "the mitochondrial genome was the primary target of selection between the two strains" .
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Environmental adaptation: COIII variations might affect metabolic efficiency under different temperature regimes, potentially explaining part of the invasive success across diverse climatic regions.
Research examining transcriptional differences between host strains has identified metabolic genes as differentially expressed, suggesting that mitochondrial function may indeed play a role in host adaptation .
What bioinformatic approaches are most effective for analyzing COIII sequence variation across populations?
For comprehensive analysis of COIII sequence variation across S. frugiperda populations, the following bioinformatic workflow is recommended:
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Sequence alignment and phylogenetic analysis:
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Haplotype network construction:
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TCS or median-joining networks to visualize relationships between haplotypes
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Population-level comparison of haplotype frequencies
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Integration with other markers:
This integrated approach has successfully identified distinct maternal lineages in invasive populations and can help track invasion pathways across continents .
