Recombinant Populus trichocarpa CASP-like protein POPTRDRAFT_751837 (POPTRDRAFT_751837)

What is the structural composition of the CASP-like protein POPTRDRAFT_751837?

POPTRDRAFT_751837 is a CASP-like protein from Populus trichocarpa (Western balsam poplar) with 203 amino acids in its full-length sequence. The amino acid sequence is: MAAAEVAVQLPESKMVTENIGGAAAAMRPFGRKAEVMNVLLRVLCMMTSVAALSSMVTAQQSSTVSIYGGMLPIQSKWSFSHSFEYVVGVSAVVAAHSLLQLLISVSRLLRKSPVIQSRSHAWLVFAGDQVFAYAMISAGAAASGVTNLNRTGIRHTALPNFCKPLQSFCDHVAVSIFFTFLSCFLLAASAVQEVIWLSRSKY . The protein is characterized by its role as a membrane-spanning domain, similar to other CASP family proteins which typically contain four transmembrane spans. Structural analysis suggests that POPTRDRAFT_751837 likely participates in membrane organization similar to other CASP proteins that are involved in forming membrane domains with specific properties for cell wall integration .

How does POPTRDRAFT_751837 relate to other CASP family proteins?

POPTRDRAFT_751837 belongs to the broader CASP (Casparian strip membrane domain proteins) family, which in Arabidopsis consists of CASP1-5 and an extended family of CASP-LIKES with 39 members . CASP proteins are homologues of occludins, which are tight junction components in animals, despite the structural differences between Casparian strips and tight junctions . While specific information about POPTRDRAFT_751837's relationship to Arabidopsis CASPs is limited in current literature, it likely shares functional characteristics with other CASP family proteins, including membrane domain formation, protein exclusion properties, and cell wall adhesion capabilities . The sequence similarities and predicted functional domains suggest evolutionary conservation of core CASP protein functions across plant species.

What are the optimal storage and handling conditions for POPTRDRAFT_751837 recombinant protein?

For optimal preservation of POPTRDRAFT_751837 activity in experimental settings, the recombinant protein should be stored in Tris-based buffer with 50% glycerol at -20°C for regular use, with long-term storage recommended at -80°C . Working aliquots can be maintained at 4°C for up to one week, but repeated freeze-thaw cycles should be strictly avoided as they significantly reduce protein functionality . When handling the protein, it's advisable to thaw aliquots on ice and maintain cold-chain conditions throughout experimental procedures. The presence of glycerol in the storage buffer acts as a cryoprotectant that prevents protein denaturation during freezing while maintaining solubility and stability of this membrane-associated protein.

What techniques are most effective for studying POPTRDRAFT_751837 localization and dynamics?

For investigating POPTRDRAFT_751837 localization and dynamics, multiple complementary approaches are recommended. Fluorescent protein tagging (GFP/YFP) of POPTRDRAFT_751837 enables visualization of its subcellular distribution and membrane domain formation when expressed in heterologous systems or native tissues. This approach has been successful with other CASP proteins, revealing their localization to specific membrane domains . For higher resolution analysis, immunogold labeling combined with electron microscopy can precisely determine the protein's association with membrane microdomains and cell wall interfaces.

To study dynamics, fluorescence recovery after photobleaching (FRAP) would be particularly valuable as CASP proteins typically show very limited lateral mobility, which is a defining characteristic . Additionally, proximity labeling methods like BioID or APEX can identify interacting partners, as demonstrated with Rab-GTPases and other CASP proteins . For temporal regulation studies, time-course experiments using transgenic lines with inducible POPTRDRAFT_751837 expression would reveal sequential events in domain formation and stabilization.

How can CRISPR-Cas9 be applied to study POPTRDRAFT_751837 function in Populus trichocarpa?

CRISPR-Cas9 genome editing offers powerful approaches for investigating POPTRDRAFT_751837 function in Populus trichocarpa. Based on successful CRISPR strategies with other CASP genes, researchers should design at least two gRNAs targeting exonic regions of POPTRDRAFT_751837 to ensure effective gene disruption . The targeting strategy should focus on conserved regions encoding transmembrane domains critical for protein function. For delivery into Populus, Agrobacterium-mediated transformation of leaf discs or cambial explants has proven effective for woody species.

Following transformation and regeneration, edited lines must undergo thorough molecular characterization including sequencing to confirm mutations. Phenotypic analysis should focus on cell wall composition, particularly examining changes in lignification patterns using histochemical stains like Basic Fuchsin or phloroglucinol, as CASP proteins influence organized lignin deposition . Additionally, permeability assays using fluorescent tracers or ion leakage measurements can assess barrier function disruption. For comprehensive functional characterization, combining POPTRDRAFT_751837 knockouts with mutations in related CASP-like genes may be necessary to overcome potential functional redundancy, as demonstrated in Arabidopsis studies .

What are the best methods for producing and purifying POPTRDRAFT_751837 for biochemical studies?

Production of high-quality POPTRDRAFT_751837 for biochemical studies requires specialized approaches due to its membrane-associated nature. For recombinant expression, bacterial systems (E. coli) using specialized strains like C41(DE3) or C43(DE3) designed for membrane proteins are recommended. Expression constructs should incorporate affinity tags determined during the production process for optimal protein folding and purification efficiency . Alternative expression systems include insect cells (Sf9) or yeast (Pichia pastoris), which often provide better membrane protein folding environments.

Purification should begin with membrane fraction isolation followed by solubilization using mild detergents such as n-dodecyl-β-D-maltoside (DDM) or digitonin to maintain native structure. Affinity chromatography using the incorporated tag enables initial purification, followed by size exclusion chromatography to obtain homogeneous protein preparations. Throughout purification, protein quality should be monitored by SDS-PAGE, western blotting, and mass spectrometry. For long-term storage, purified protein should be maintained in buffer containing 50% glycerol at -20°C or -80°C, with working aliquots kept at 4°C for maximum one week to prevent functional deterioration .

How can POPTRDRAFT_751837 be used to study membrane-wall microdomain formation?

POPTRDRAFT_751837 represents an excellent model for investigating membrane-wall microdomain formation processes. Research approaches should capitalize on CASP proteins' unique properties of creating stable, immobile membrane domains that interface with specific cell wall regions . Experimentally, researchers can generate tagged POPTRDRAFT_751837 constructs (fluorescent or epitope tags) to visualize domain formation in real-time using super-resolution microscopy techniques such as STORM or PALM, which provide nanometer-scale resolution of membrane organization.

To analyze the critical stages of domain establishment, time-lapse imaging of POPTRDRAFT_751837 localization during cell development would reveal the temporal sequence of events. Co-expression with markers for secretory pathway components, particularly exocyst complex proteins and Rab GTPases, would illuminate the mechanisms of directed membrane domain growth . Researchers should examine how POPTRDRAFT_751837 influences vesicle tethering factors, as CASP proteins have been shown to displace initial secretory foci by excluding these factors . This experimental design allows for testing the hypothesis that POPTRDRAFT_751837 creates exclusion zones that redirect secretion vectors, essential for forming continuous barrier structures.

What protein complexes does POPTRDRAFT_751837 likely form in vivo?

POPTRDRAFT_751837 likely participates in multiple protein complexes essential for its barrier-forming functions. Based on studies of related CASP proteins, POPTRDRAFT_751837 would be expected to form homo-oligomeric complexes with itself and hetero-oligomeric assemblies with other CASP-like proteins through extensive cross-interactions . These interactions create a scaffold that establishes specialized membrane domains. Additionally, proximity labeling studies with other CASP proteins have identified Rab-GTPases as potential interacting partners, specifically members of the RabA subfamily that function as exocyst activators .

The protein may also interact with cell wall-localized proteins similar to ENHANCED SUBERIN 1 (ESB1), which localizes to Casparian strips and is involved in their formation . Though direct physical interactions between CASPs and cell wall enzymes remain largely indirect, functional studies suggest associations with NADPH oxidases and peroxidases that regulate reactive oxygen species required for lignin polymerization . Investigation of these complexes requires approaches like co-immunoprecipitation with tagged POPTRDRAFT_751837, cross-linking mass spectrometry, or proximity labeling techniques that can capture transient interactions in membrane environments.

What is the predicted role of POPTRDRAFT_751837 in stress response mechanisms?

POPTRDRAFT_751837 likely plays significant roles in stress response mechanisms, particularly related to barrier function regulation in response to environmental challenges. While direct evidence for POPTRDRAFT_751837's stress response function is limited, its structural and functional similarities to other CASP proteins suggest potential roles in maintaining barrier integrity under stress conditions. In Arabidopsis, CASP-mediated barriers respond to integrity threats through the SCHENGEN pathway, which boosts barrier formation and initiates compensatory lignification when defects occur .

POPTRDRAFT_751837 may participate in similar surveillance mechanisms in Populus trichocarpa, with its expression and localization potentially modulated during stress exposure. For experimental investigation, researchers should analyze POPTRDRAFT_751837 expression under various abiotic stresses (drought, salinity, temperature extremes) using qRT-PCR and RNA-seq approaches. Similar to TCP genes in Populus that show stress-responsive expression patterns , POPTRDRAFT_751837 may be regulated by specific transcription factors activated during stress. Generating stress-inducible promoter reporter constructs would help identify regulatory elements controlling POPTRDRAFT_751837 expression under different environmental conditions.

How does POPTRDRAFT_751837 compare to CASP proteins in Arabidopsis thaliana?

POPTRDRAFT_751837 from Populus trichocarpa shares fundamental structural and functional characteristics with Arabidopsis CASP proteins while exhibiting species-specific adaptations. Both contain multiple transmembrane domains characteristic of the MARVEL protein superfamily to which CASPs belong . In Arabidopsis, CASP1-5 show strong endodermis-specific expression and form the Casparian Strip membrane domain (CSD), creating protein exclusion zones with strong cell wall attachment . While direct experimental evidence for POPTRDRAFT_751837's tissue-specific expression is limited, its sequence similarity suggests conservation of core CASP functions.

The table below compares key features of POPTRDRAFT_751837 with Arabidopsis CASPs:

Evolutionary analysis suggests that while core functions are conserved, species-specific adaptations likely exist to accommodate the different anatomy and environmental challenges faced by trees versus herbaceous plants .

What insights does comparative genomics provide about POPTRDRAFT_751837 evolution?

Comparative genomic analysis reveals that POPTRDRAFT_751837 likely evolved through the significant genome duplication events that shaped the Populus lineage. Populus trichocarpa underwent a relatively recent whole genome duplication (rWGD) near the Cretaceous-Paleogene boundary after diverging from Arabidopsis, which contributed to gene family expansion throughout the genome . This evolutionary history explains why Populus contains expanded gene families, as seen with TCP transcription factors (36 in Populus versus 24 in Arabidopsis) .

The CASP-like gene family likely followed similar expansion patterns, with POPTRDRAFT_751837 representing one member of this expanded family. This gene family expansion may have enabled sub-functionalization or neo-functionalization of CASP-like proteins in Populus, potentially allowing for specialized roles in woody plant development and stress responses. Analysis of synonymous substitution (Ks) values between paralogous sequences would help date POPTRDRAFT_751837's emergence and determine if it resulted from the most recent WGD or older duplication events .

The conservation of POPTRDRAFT_751837 in Populus suggests strong selective pressure maintaining its function, highlighting its biological importance. Researchers interested in evolutionary perspectives should perform phylogenetic analyses comparing POPTRDRAFT_751837 with homologs from other woody and herbaceous species to reconstruct the evolutionary history of this gene family across plant lineages.

What are common challenges in expressing and purifying POPTRDRAFT_751837?

Researchers working with POPTRDRAFT_751837 face several technical challenges inherent to membrane proteins. Membrane protein overexpression often leads to toxicity, misfolding, and aggregation in heterologous systems, requiring careful optimization. Expression in standard E. coli systems frequently results in inclusion bodies, necessitating specialized strains designed for membrane proteins or alternative expression systems like yeast or insect cells. The hydrophobic nature of transmembrane domains presents solubility challenges during purification, requiring optimization of detergent types and concentrations.

Another significant challenge is maintaining protein stability during purification. POPTRDRAFT_751837 requires specialized buffer systems containing glycerol (typically 50%) for stability . Researchers often encounter difficulties achieving high purity while maintaining native conformation and function. To address these challenges, expression constructs should be designed with solubility-enhancing tags, and expression conditions must be carefully optimized for temperature, induction time, and inducer concentration. For purification, screening multiple detergents is essential, with milder options like digitonin or DDM often preferred over harsh detergents like SDS that denature membrane proteins.

How can researchers verify the functional integrity of purified POPTRDRAFT_751837?

Verifying the functional integrity of purified POPTRDRAFT_751837 requires multiple complementary approaches. First, researchers should perform circular dichroism (CD) spectroscopy to assess secondary structure integrity, confirming the expected alpha-helical content typical of transmembrane proteins. Thermal shift assays provide information about protein stability under various buffer conditions, helping optimize stabilization additives. Since CASP proteins form homotypic interactions, size exclusion chromatography coupled with multi-angle light scattering (SEC-MALS) can verify oligomerization states corresponding to functional complexes.

For functional validation, researchers can develop in vitro reconstitution assays where purified POPTRDRAFT_751837 is incorporated into liposomes or nanodiscs to assess its membrane organization properties. Specific antibodies against POPTRDRAFT_751837 can be used in immunolocalization studies to confirm that recombinant protein retains native binding and localization patterns when applied to plant tissue sections. Additionally, interaction studies using surface plasmon resonance (SPR) or microscale thermophoresis (MST) with potential binding partners identified from related CASP proteins, such as Rab GTPases , would confirm binding functionality. These multiple lines of evidence collectively establish that purified POPTRDRAFT_751837 maintains its native structural and functional properties.

What emerging technologies could advance understanding of POPTRDRAFT_751837 function?

Several cutting-edge technologies hold promise for deepening our understanding of POPTRDRAFT_751837 function. Cryo-electron microscopy (cryo-EM) could reveal the three-dimensional structure of POPTRDRAFT_751837 alone and in complexes with interacting partners, providing atomic-level insights into membrane integration and protein-protein interactions. Advanced lattice light-sheet microscopy with adaptive optics would enable long-term imaging of POPTRDRAFT_751837 dynamics in living plant tissues with minimal phototoxicity, capturing the process of membrane domain formation in unprecedented detail.

Proximity-dependent biotinylation approaches like TurboID, which have faster kinetics than traditional BioID, could map the POPTRDRAFT_751837 interactome with temporal resolution, identifying transient interactions during different stages of domain assembly . Single-cell and spatial transcriptomics would provide insights into the cell-specific expression patterns of POPTRDRAFT_751837 and co-regulated genes across tissues and developmental stages. CRISPR base editing and prime editing technologies offer precise genetic manipulation capabilities to introduce specific amino acid changes without double-strand breaks, enabling detailed structure-function analysis of POPTRDRAFT_751837 in its native genomic context.

How might POPTRDRAFT_751837 research contribute to understanding plant adaptation to environmental stresses?

Research on POPTRDRAFT_751837 may significantly advance our understanding of plant adaptation to environmental stresses through several mechanisms. As a component of barrier-forming structures, POPTRDRAFT_751837 likely contributes to regulating water and solute movement, critical processes during drought, salinity, and temperature stresses. Studies could investigate how POPTRDRAFT_751837 expression, localization, and complex formation change under stress conditions, potentially revealing stress-specific adaptations of barrier properties.

Similar to how TCP genes in Populus trichocarpa show stress-responsive expression and contribute to cold tolerance , POPTRDRAFT_751837 may participate in specialized stress response pathways unique to woody perennials. Investigating POPTRDRAFT_751837 regulation during seasonal changes could reveal how barrier properties are modulated during winter dormancy versus active growth, contributing to our understanding of stress preparation mechanisms in trees. Comparative studies between POPTRDRAFT_751837 and homologs from Populus species adapted to different environmental niches could identify adaptive variations that contribute to stress resilience.

This research has broader implications for understanding evolutionary adaptations in long-lived woody species facing climate change pressures. Discoveries about POPTRDRAFT_751837's role in stress adaptation could potentially inform biotechnological approaches to enhancing stress tolerance in economically important tree species and crops.