Recombinant Nicotiana tomentosiformis Apocytochrome f (petA)
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Target Background
KEGG: nto:3776356
Q&A
What is Apocytochrome f (petA) and why is it studied in Nicotiana tomentosiformis?
Apocytochrome f (petA) is a precursor protein of cytochrome f, a crucial component of the cytochrome b6f complex involved in photosynthetic electron transport. Nicotiana tomentosiformis serves as an excellent model system for studying this protein due to its well-characterized genome, facile transformation techniques, and its facultative short-day flowering behavior. As one of the progenitor species of cultivated tobacco (Nicotiana tabacum), N. tomentosiformis provides valuable comparative insights into evolutionary adaptations of photosynthetic machinery. The petA gene has been isolated from N. tomentosiformis alongside other Nicotiana species, allowing researchers to conduct detailed analyses of gene expression patterns and protein functionality .
What expression systems are suitable for recombinant Apocytochrome f production?
Several expression systems can be used for recombinant Apocytochrome f (petA) production, each offering distinct advantages:
| Host System | Expression Time | Yield | Post-translational Modifications | Applications |
|---|---|---|---|---|
| E. coli | 24-48 hours | High | Limited | Structural studies, antibody production |
| Yeast | 2-4 days | High | Moderate | Functional studies |
| Insect cells | 3-5 days | Moderate | Advanced | Activity assays, complex interactions |
| Mammalian cells | 7-14 days | Low | Extensive | Studies requiring native folding |
| Nicotiana species | 3-7 days | Variable | Plant-specific | Plant-based studies, comparative analyses |
How does N. tomentosiformis differ from other Nicotiana species as an expression system?
Nicotiana tomentosiformis exhibits distinct physiological and genetic characteristics compared to other Nicotiana species. It demonstrates facultative short-day flowering behavior, unlike N. sylvestris which strictly flowers under long-day conditions . This differing photoperiodic response correlates with unique expression patterns of key regulatory genes like NtomCOL2, which may influence recombinant protein expression under varying light conditions.
N. tomentosiformis contributed to the genetic makeup of the tetraploid N. tabacum, but retains unique gene regulation mechanisms that can affect heterologous protein expression. When designing expression systems in N. tomentosiformis, researchers should consider these species-specific characteristics, particularly when timing harvest for maximum protein yield .
What are the optimal growth conditions for N. tomentosiformis when expressing recombinant Apocytochrome f?
For optimal recombinant protein expression in N. tomentosiformis, implement the following growth conditions:
| Parameter | Vegetative Growth | Reproductive Phase | Notes |
|---|---|---|---|
| Photoperiod | 8h light (SD) or 16h light (LD) | SD preferred (8h) | Photoperiod affects NtomCOL2 expression |
| Light intensity | 200 μmol m⁻² s⁻¹ (SD) | 200 μmol m⁻² s⁻¹ (SD) | Higher intensities may stress plants |
| Temperature | 25-27°C (light), 20°C (dark) | 25-27°C (light), 20°C (dark) | Temperature fluctuation mimics natural conditions |
| Media | MS medium for sterile cultivation | Soil for mature plants | Sterile conditions for initial transformants |
| Humidity | 60-70% | 60-70% | Prevents physiological stress |
These conditions are based on experimental protocols that have successfully maintained N. tomentosiformis plants while studying gene expression patterns. When cultivating plants for protein expression, harvest tissues 4 hours after dawn when gene expression levels peak for many nuclear-encoded chloroplast proteins, including those involved in the photosynthetic apparatus .
What transformation methods are most effective for expressing Apocytochrome f in N. tomentosiformis?
The most effective transformation methods for N. tomentosiformis include:
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Agrobacterium-mediated transformation: This method has been successfully used for stable transformation of N. tomentosiformis, allowing for integration of the recombinant petA gene into the plant genome. Plants should be germinated and grown under sterile conditions (16-hour photoperiod, 23°C, 100 μmol m⁻² s⁻¹) on MS medium before transformation .
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Transient expression systems: For rapid screening and optimization, transient expression using recombinant plant viral vectors offers significant advantages. These systems allow for expression scale-up and construct optimization without requiring the time-intensive process of generating stable transgenic lines .
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CRISPR/Cas9 gene editing: For studies requiring modification of the native petA gene, CRISPR/Cas9 has been successfully employed in Nicotiana species. For N. tomentosiformis specifically, the protocol should be adapted from those established for related species with appropriate guide RNA design targeting the specific petA locus .
Each method should be optimized based on the specific experimental objectives, with transformation efficiency verified through molecular techniques such as PCR, qPCR, and immunoblotting.
What extraction methods yield the highest quality Apocytochrome f protein from N. tomentosiformis leaf tissue?
Extraction of high-quality recombinant Apocytochrome f from N. tomentosiformis leaf tissues can be achieved through several approaches, each optimized for different experimental objectives:
| Extraction Method | Buffer Composition | Applications | Protein Quality |
|---|---|---|---|
| Total protein extraction | 50mM Tris-HCl (pH 7.5), 150mM NaCl, 1mM EDTA, 10% glycerol, protease inhibitors | Maximum yield, initial screening | Moderate |
| Chloroplast isolation | 330mM sorbitol, 50mM HEPES (pH 7.6), 1mM MgCl₂, 1mM EDTA | Native conformation studies | High |
| Apoplastic fluid collection | 100mM Tris-HCl (pH 7.0), 10mM MgCl₂, 1mM EDTA | Secreted protein fraction | Very high |
| Membrane protein extraction | 50mM HEPES (pH 7.5), 0.3M sucrose, 10mM NaCl, 1% detergent | Membrane-associated studies | High for membrane proteins |
For maximum yield of functionally relevant protein, harvest leaves approximately 4-8 hours after dawn when photosynthetic gene expression typically peaks. Immediately freeze harvested tissue in liquid nitrogen and store at -80°C until extraction to preserve protein integrity . During extraction, maintain temperatures below 4°C and include appropriate protease inhibitors to prevent degradation.
How does the expression of Apocytochrome f in N. tomentosiformis compare to expression in its close relative N. tabacum?
The expression dynamics of Apocytochrome f in N. tomentosiformis differ significantly from those in N. tabacum due to their distinct evolutionary backgrounds and photoperiodic behaviors. N. tomentosiformis, as a progenitor species of N. tabacum, exhibits facultative short-day flowering, whereas N. tabacum demonstrates day-neutral flowering characteristics .
This fundamental difference influences gene expression patterns, including those genes potentially involved in regulating chloroplast proteins like Apocytochrome f. Comparative studies have shown that regulatory elements like NtomCOL2 (in N. tomentosiformis) and NtCOL2a/b (in N. tabacum) display similar diurnal expression profiles with peaks around dawn, but with subtle species-specific variations that can affect downstream protein expression .
When designing expression systems, these differences must be considered:
| Species | Optimal Expression Conditions | Regulatory Considerations | Protein Yield Characteristics |
|---|---|---|---|
| N. tomentosiformis | Short-day conditions preferred | NtomCOL2 influences gene expression patterns | Higher expression in mature medial leaves |
| N. tabacum | Day-neutral, flexible conditions | NtCOL2a/b expression less photoperiod-dependent | More consistent expression across photoperiods |
For maximum comparative accuracy, harvest tissues at equivalent developmental stages and precise diurnal time points when studying expression differences between these species .
What cellular localization techniques are most effective for studying Apocytochrome f targeting in N. tomentosiformis?
For studying Apocytochrome f targeting in N. tomentosiformis, several cellular localization techniques have proven effective:
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Fluorescent protein fusion: Creating translational fusions between Apocytochrome f and fluorescent proteins like Venus or GFP allows visualization of protein localization. When expressed in N. benthamiana leaf epidermal cells (a closely related model system), fusion proteins can be detected in specific cellular compartments, particularly the nucleus for many transcription factors involved in photosynthetic gene regulation .
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Subcellular fractionation: Differential centrifugation to isolate chloroplasts, followed by further fractionation into thylakoid membranes and stroma, can determine the precise localization of the mature protein and processing intermediates.
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Immunolocalization: Using antibodies specific to Apocytochrome f or epitope tags allows visualization of the native protein through confocal microscopy.
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Reporter gene assays: For studying the expression patterns, promoter-reporter constructs (such as β-glucuronidase or luciferase) can be developed to identify tissues and cellular contexts where the petA gene is actively transcribed .
When designing fusion proteins, consider that N-terminal signal sequences are critical for chloroplast targeting, and C-terminal fusions are generally preferable to avoid disrupting targeting signals.
How do diurnal expression patterns affect recombinant Apocytochrome f production in N. tomentosiformis?
Diurnal expression patterns significantly impact recombinant Apocytochrome f production in N. tomentosiformis. Research has demonstrated that genes encoding photosynthetic components, including regulatory elements like NtomCOL2, exhibit strong diurnal expression profiles with peaks typically occurring around dawn .
The following graph represents typical diurnal expression patterns observed in N. tomentosiformis:
| Zeitgeber Time (h) | 0 | 4 | 8 | 12 | 16 | 20 | 24 |
|---|---|---|---|---|---|---|---|
| Relative Expression (LD) | 1.0 | 0.7 | 0.3 | 0.2 | 0.4 | 0.8 | 1.0 |
| Relative Expression (SD) | 1.0 | 0.8 | 0.3 | 0.1 | 0.3 | 0.5 | 0.9 |
These expression patterns have practical implications for harvesting strategies:
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For maximum yield of endogenous or recombinant proteins regulated by native promoters, harvest tissue 0-4 hours after dawn when expression typically peaks.
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When using constitutive promoters (like P35S) for recombinant expression, diurnal patterns may still affect protein accumulation due to interactions with endogenous regulatory networks.
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Expression may differ between vegetative and reproductive developmental stages, with studies showing NtomCOL2 expression patterns remain relatively consistent across both stages .
Understanding these patterns allows researchers to optimize harvest timing and potentially manipulate light conditions to maximize recombinant protein production.
What strategies can overcome low expression levels of recombinant Apocytochrome f in N. tomentosiformis?
When facing low expression levels of recombinant Apocytochrome f in N. tomentosiformis, researchers can implement several optimization strategies:
| Issue | Strategy | Methodological Approach | Expected Outcome |
|---|---|---|---|
| Weak promoter activity | Promoter substitution | Replace native promoter with stronger alternatives (e.g., 35S, ubiquitin) or inducible systems | 2-10 fold increase in expression |
| Poor mRNA stability | Codon optimization | Adapt coding sequence to N. tomentosiformis codon usage preferences | 1.5-3 fold increase in expression |
| Protein degradation | Protease inhibition | Include protease inhibitors in extraction buffer; target specific plant proteases | Improved protein recovery |
| Inefficient translation | 5' UTR enhancement | Include appropriate plant translation enhancer sequences | 2-4 fold increase in mRNA translation |
| Poor timing | Harvest optimization | Sample at optimal diurnal timepoints (dawn or 4h after dawn) | Up to 5 fold increase in yield |
Additionally, transient expression systems derived from recombinant plant viral vectors offer opportunities for rapid expression screening and construct optimization before committing to stable transformation . For maximum expression, consider evaluating different tissues, as studies have shown highest expression of related genes in mature medial and basal leaves of Nicotiana species .
How can researchers address post-translational modification issues with recombinant Apocytochrome f?
Post-translational modifications (PTMs) are critical for proper Apocytochrome f function. Researchers can address PTM-related issues through several approaches:
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Expression system selection: While E. coli and yeast systems provide high yields and shorter turnaround times, they may lack the necessary machinery for plant-specific PTMs. For studies requiring authentic plant PTMs, expression within N. tomentosiformis itself or other plant-based systems is preferable .
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Chloroplast targeting optimization: Ensure that the transit peptide sequence is intact and properly functioning. If necessary, replace with known efficient chloroplast transit peptides from other well-characterized photosynthetic proteins.
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Co-expression of modification enzymes: Identify and co-express enzymes involved in specific PTMs required for proper Apocytochrome f function.
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Membrane integration assessment: For proper function, cytochrome f must be correctly integrated into thylakoid membranes. Analyze membrane fraction purity and protein orientation using protease protection assays.
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Comparative analysis: Perform side-by-side comparisons of PTMs in recombinant versus native proteins using mass spectrometry to identify specific modifications that may be missing or altered.
For recombinant proteins requiring complex PTMs, insect cell expression with baculovirus vectors or mammalian cell expression systems can provide many of the necessary modifications while maintaining reasonable yields .
What controls are essential for validating recombinant Apocytochrome f functionality in experimental systems?
Rigorous controls are essential for validating recombinant Apocytochrome f functionality:
| Control Type | Implementation | Purpose | Expected Outcome |
|---|---|---|---|
| Positive control | Native Apocytochrome f isolated from wild-type N. tomentosiformis | Establishes baseline for normal function | Benchmark activity levels |
| Negative control | Empty vector transformants | Confirms phenotypic changes are due to recombinant protein | No activity/complementation |
| Expression verification | Western blot with anti-Apocytochrome f antibodies | Confirms target protein expression | Detectable protein band at expected MW |
| Localization control | Chloroplast markers (e.g., RbcS) | Verifies proper targeting to chloroplasts | Co-localization with marker |
| Functional assay | Electron transport measurements | Assesses functional integration into photosynthetic machinery | Restoration of electron flow in deficient systems |
| Complementation test | Expression in petA-deficient mutants | Confirms biological activity | Restoration of photosynthetic function |
| Site-directed mutagenesis | Engineered mutations at key functional residues | Validates structure-function relationships | Predictable activity changes |
When studying diurnal expression patterns, include multiple timepoints throughout the day-night cycle to capture the complete expression profile. Research on related Nicotiana genes shows distinct expression patterns with peaks typically occurring around dawn .
How can recombinant Apocytochrome f studies in N. tomentosiformis contribute to photosynthesis research?
Recombinant Apocytochrome f studies in N. tomentosiformis offer unique opportunities to advance photosynthesis research through several approaches:
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Comparative studies across Nicotiana species: The evolutionary relationship between N. tomentosiformis and other Nicotiana species, including N. tabacum and N. sylvestris, provides a natural experimental system for studying the adaptation and optimization of photosynthetic machinery. Differences in photosynthetic efficiency can be correlated with sequence and structural variations in Apocytochrome f .
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Structure-function analysis: Site-directed mutagenesis of recombinant Apocytochrome f can reveal the functional significance of specific amino acid residues within the protein, contributing to our understanding of electron transport mechanisms.
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Environmental adaptation studies: N. tomentosiformis responds to photoperiodic cues differently than other Nicotiana species, with facultative short-day flowering behavior . This makes it valuable for studying how photosynthetic components adapt to different light regimes.
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Metabolic engineering platform: As plant-based expression systems become increasingly important for recombinant protein production, understanding the integration of foreign proteins into the photosynthetic machinery of N. tomentosiformis can inform strategies for using plants as biofactories for complex proteins .
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Climate change adaptation research: Manipulating Apocytochrome f expression can help explore photosynthetic adaptations to changing environmental conditions, potentially contributing to the development of crops with enhanced climate resilience.
What emerging technologies could enhance recombinant protein expression in Nicotiana species?
Several emerging technologies show promise for enhancing recombinant protein expression in Nicotiana species:
Particularly promising is the combination of transient expression systems derived from recombinant plant viral vectors with genome editing technologies. These approaches offer opportunities for rapid expression screening, construct optimization, and expression scale-up without permanent genetic modification . Additionally, advanced imaging techniques coupled with fluorescent protein fusions allow real-time monitoring of protein expression and localization in living plant tissues .
How might advances in understanding N. tomentosiformis gene regulation influence recombinant protein production strategies?
Recent advances in understanding N. tomentosiformis gene regulation have significant implications for recombinant protein production strategies:
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Diurnal regulation insights: Studies of genes like NtomCOL2 reveal distinct diurnal expression patterns in N. tomentosiformis, with expression typically peaking around dawn and showing specific patterns under different day-length conditions . This knowledge can inform harvest timing and light condition optimization for maximum recombinant protein yield.
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Photoperiod response mechanisms: As a facultative short-day flowering plant, N. tomentosiformis possesses unique regulatory networks that respond to photoperiod changes . Understanding these mechanisms allows for manipulating growth conditions to enhance recombinant protein expression while controlling flowering and development.
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Progenitor-derived regulatory elements: The relationship between N. tomentosiformis and N. tabacum provides insights into how regulatory elements evolved during polyploidization. Research shows that while genes like NtomCOL2 and its N. tabacum homologs (NtCOL2a/b) share similar expression patterns, subtle differences exist that may affect downstream protein accumulation .
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Tissue-specific expression profiling: Studies indicate that expression levels of many regulatory genes are highest in mature medial and basal leaves and lowest in the stem . This spatial expression information can guide tissue selection for optimal recombinant protein production.
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Cell-specific expression: Promoter-reporter analyses reveal cell-type specific expression patterns, such as phloem companion cell-specific expression for some regulatory factors in Nicotiana . This knowledge enables the development of highly targeted expression systems for recombinant proteins.
What are the key considerations for establishing a successful recombinant Apocytochrome f research program using N. tomentosiformis?
Establishing a successful recombinant Apocytochrome f research program using Nicotiana tomentosiformis requires careful consideration of several key factors:
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Expression system selection: Choose between stable transformation and transient expression based on research objectives. While stable transformation provides consistent expression across generations, transient expression systems offer rapid results for preliminary studies and optimization .
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Growth condition optimization: Implement precise control of photoperiod, temperature, and light intensity based on N. tomentosiformis' physiological requirements. Consider its facultative short-day flowering behavior when planning experimental timelines .
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Harvest timing strategy: Coordinate tissue collection with diurnal expression patterns, typically harvesting 0-4 hours after dawn when expression of many photosynthesis-related genes peaks .
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Extraction protocol development: Establish efficient protein extraction methods tailored to Apocytochrome f's membrane-associated nature and specific research objectives .
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Rigorous experimental controls: Include appropriate positive and negative controls for expression verification, functional assessment, and localization studies .
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Interdisciplinary collaboration: Combine expertise in molecular biology, plant physiology, biochemistry, and structural biology to address the multifaceted challenges of recombinant protein research.
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Comparative approach: Leverage the evolutionary relationship between N. tomentosiformis and other Nicotiana species to gain deeper insights into protein function and regulation .
