Recombinant Arabidopsis thaliana Defender against cell death 2 (DAD2)
Description
Protein Structure and Composition
Arabidopsis thaliana Defender against cell death 2 (DAD2) is a relatively small protein composed of 115 amino acids with a molecular structure optimized for its role in cellular protection and glycosylation processes. The full amino acid sequence of DAD2 has been identified as MVKSTSKDAQDLFHSLHSAYTATPTNLKIIDLYVCFAVFTALIQVAYMALVGSFPFNSFLSGVLSCIGTAVLAVCLRIQVNKENKEFKDLAPERAFADFVLCNLVLHLVIINFLG, which contains specific domains critical for its interaction with other cellular components . Analysis of the protein structure suggests that DAD2 contains hydrophobic regions that likely facilitate its integration into cellular membranes, particularly the endoplasmic reticulum where it participates in protein glycosylation processes. The protein's compact size and specific sequence characteristics enable it to function effectively in its role as a defender against programmed cell death mechanisms. Structural studies indicate that DAD2 shares significant homology with other anti-apoptotic proteins, suggesting evolutionary conservation of cell death regulatory mechanisms across kingdoms .
Genetic Background and Expression
The DAD2 gene is identified in the Arabidopsis thaliana genome with the locus name At2g35520 and ORF name T32F12.10, encoding the full-length protein that functions as a critical regulator of cellular processes . The gene is expressed under various conditions in Arabidopsis tissues, with expression patterns often responding to environmental stressors, particularly those inducing oxidative damage. In transcriptomic analyses, DAD2 expression has been shown to be regulated under specific stress conditions, suggesting its role in plant adaptive responses. The gene for DAD2 encodes a protein that is assigned the UniProt identifier O22622, which provides standardized information about its molecular characteristics and functional annotations . DAD2 is sometimes referred to by its synonyms AtDAD2 or DAD-2 in the scientific literature, reflecting its relationship to similar proteins in other organisms . Research suggests that DAD2 expression may be particularly important during plant development stages where controlled cell death is critical for proper tissue formation and function .
Expression Systems and Purification Methods
Recombinant Arabidopsis thaliana DAD2 protein is typically produced using bacterial expression systems, with E. coli being the predominant host for efficient protein production . The recombinant protein is commonly engineered with an N-terminal His-tag, which facilitates the subsequent purification process through affinity chromatography techniques. The expression construct typically contains the full-length DAD2 sequence (amino acids 1-115) to ensure complete functionality of the recombinant protein. Following expression, the protein undergoes a series of purification steps to achieve high purity, with commercially available recombinant DAD2 preparations typically exceeding 90% purity as determined by SDS-PAGE analysis . The purified recombinant protein is often provided in lyophilized powder form, which enhances its stability during storage and shipping. Special care is taken during the purification process to maintain the native conformation of the protein, which is essential for functional studies and applications requiring biological activity .
Physical and Chemical Properties
The recombinant DAD2 protein exhibits specific physical and chemical properties that influence its handling, storage, and application in research settings. The protein is typically stable when stored properly but is sensitive to repeated freeze-thaw cycles, which can compromise its structural integrity and functional properties . For optimal stability, the recombinant DAD2 is often supplied in a Tris/PBS-based buffer containing 6% trehalose at pH 8.0, with the trehalose serving as a cryoprotectant to maintain protein structure during freeze-thaw processes . When reconstituting the lyophilized protein, it is recommended to use deionized sterile water to achieve a concentration of 0.1-1.0 mg/mL, with the addition of 5-50% glycerol for long-term storage at -20°C/-80°C . The physical properties of recombinant DAD2 make it suitable for various biochemical and functional assays, including studies of protein-protein interactions, enzymatic activities, and cellular responses. Working aliquots of reconstituted protein can be stored at 4°C for up to one week without significant loss of activity, facilitating experimental workflows .
| Property | Details |
|---|---|
| Protein Length | Full Length (1-115 amino acids) |
| Source | Expressed in E. coli |
| Tag | N-terminal His tag |
| Form | Lyophilized powder |
| Purity | Greater than 90% (SDS-PAGE) |
| Storage Buffer | Tris/PBS-based buffer, 6% Trehalose, pH 8.0 |
| Recommended Storage | -20°C/-80°C, avoid repeated freeze-thaw cycles |
| Working Aliquot Storage | 4°C for up to one week |
| Reconstitution | Deionized sterile water (0.1-1.0 mg/mL) with 5-50% glycerol |
Regulation of Programmed Cell Death
DAD2 serves as a crucial negative regulator of programmed cell death in Arabidopsis thaliana, functioning as part of the plant's sophisticated mechanisms for controlling cellular fate under various conditions . Experimental evidence demonstrates that overexpression of DAD2 protects plants from photooxidative stress and delays the onset of senescence, highlighting its protective role in cellular survival pathways. The protein appears to function similarly to its homolog DAD1, with both proteins showing the ability to rescue cells from stress-induced programmed cell death when overexpressed . Knock-out mutants of DAD2 exhibit increased sensitivity to stress conditions and accelerated cell death responses, further confirming its role as a defender against apoptotic processes in plant cells . The functional significance of DAD2 in programmed cell death regulation is underscored by its ability to influence downstream signaling cascades that determine whether cells undergo death or activate survival mechanisms. Interestingly, the function of DAD2 appears to be evolutionarily conserved, as evidenced by the ability of Arabidopsis DAD1, a close homolog, to rescue apoptotic phenotypes in animal cell systems .
Antagonistic Relationship with OXI1 Kinase Pathway
Research has revealed a significant antagonistic relationship between DAD2 and the OXIDATIVE STRESS INDUCIBLE 1 (OXI1) kinase in regulating plant responses to high light stress and programmed cell death . This antagonistic action represents a sophisticated regulatory mechanism whereby the balance between these two proteins determines whether plants activate cell death or survival pathways under stress conditions. Overexpression studies have shown that DAD2 overexpression decreases OXI1 expression, effectively reducing jasmonate levels and decreasing plant sensitivity to photooxidative stress . Conversely, knock-out mutants of DAD2 exhibit elevated OXI1 expression, increased jasmonate accumulation, and enhanced susceptibility to stress-induced cell death, demonstrating the regulatory balance between these two proteins . This antagonistic relationship appears to be part of a complex signaling network that integrates information about environmental conditions and determines appropriate cellular responses. The DAD2-OXI1 regulatory axis represents an important control point in plant stress physiology, with significant implications for understanding how plants balance growth, development, and stress responses .
Role in Protein Glycosylation
Beyond its function in cell death regulation, DAD2 has been implicated in protein glycosylation processes, particularly in N-glycosylation pathways critical for proper protein folding and function . DAD2 is identified as a putative ortholog of yeast suppressor of Wbp1 (Swp1p)/mammalian ribophorin II and OST2/DAD1, suggesting a conserved role in the oligosaccharyltransferase (OST) complex that mediates N-glycosylation in the endoplasmic reticulum . While the specific mechanisms remain to be fully elucidated, evidence suggests that DAD2 contributes to the proper functioning of the N-glycosylation machinery in plant cells. The dual function of DAD2 in both glycosylation and cell death regulation suggests potential mechanistic links between these cellular processes, possibly through the quality control of glycoproteins and the unfolded protein response . Proper N-glycosylation is essential for the stability and function of many proteins involved in stress responses, potentially explaining how DAD2's role in glycosylation connects to its function in stress tolerance and cell death regulation. The involvement of DAD2 in these fundamental cellular processes highlights its importance in maintaining cellular homeostasis under normal and stress conditions .
Photooxidative Stress and Light-Induced Cell Death
DAD2 plays a significant role in protecting plants against photooxidative stress and light-induced cell death, mechanisms that are particularly important in photosynthetic organisms exposed to variable light environments. Under high light conditions, plants can experience photooxidative damage that leads to the generation of reactive oxygen species (ROS) and potentially triggers programmed cell death if protective mechanisms are insufficient . Research demonstrates that DAD2 is part of these protective mechanisms, with overexpression of DAD2 significantly reducing plant sensitivity to high light and delaying light-induced cell death responses. The protective effect of DAD2 against photooxidative stress appears to involve modulation of hormone signaling pathways, particularly those involving jasmonate and salicylate, which are known mediators of stress responses in plants . The function of DAD2 in photooxidative stress response may be particularly relevant in natural environments where plants experience fluctuating light conditions and must rapidly adjust their cellular protection mechanisms. Interestingly, transcriptomic analyses have shown that DAD1, a homolog of DAD2, is induced under acclimatory light conditions rather than under conditions leading to programmed cell death, suggesting a possible protective role against singlet oxygen-induced cell death .
Phytohormone Signaling and Defense Responses
DAD2 exerts significant influence on plant hormone signaling pathways, particularly those involving jasmonate and salicylate, which are critical regulators of defense responses and programmed cell death . Experimental evidence indicates that DAD2 overexpression leads to decreased jasmonate levels and consequently reduced sensitivity to stress conditions that would normally trigger defense responses. This hormonal regulation appears to be a key mechanism through which DAD2 modulates plant stress responses and cell death pathways. The relationship between DAD2 and hormone signaling creates a sophisticated regulatory network that allows plants to fine-tune their responses to various environmental challenges . Salicylate, in particular, has been shown to play a crucial role in programmed cell death downstream of jasmonate, with exogenous applications of jasmonate upregulating salicylate biosynthesis genes and causing leaf damage in wild-type plants but not in salicylate biosynthesis mutants . The interplay between DAD2, OXI1, and phytohormones reveals a complex signaling cascade that determines whether plants activate cell protection mechanisms or initiate programmed cell death in response to stress. This regulatory system highlights the sophisticated balance between different signaling pathways that plants have evolved to optimize their survival under variable environmental conditions .
Model System for Studying Programmed Cell Death
Recombinant DAD2 provides researchers with a valuable tool for investigating the molecular mechanisms underlying programmed cell death in plants, offering insights that may extend to other organisms due to the evolutionary conservation of these pathways. The availability of purified recombinant DAD2 enables detailed biochemical and structural studies that can reveal the protein's interaction partners, post-translational modifications, and mechanistic functions in cell death regulation. By studying the effects of DAD2 overexpression or knockout in model plant systems, researchers can elucidate the complex signaling networks that determine cell fate decisions under various stress conditions . The antagonistic relationship between DAD2 and OXI1 represents a particularly interesting model for understanding how plants balance competing signaling pathways to optimize their responses to environmental challenges. The functional conservation between plant DAD proteins and their counterparts in other organisms suggests that findings from plant systems may have broader implications for understanding cell death regulation across different life forms . Future research using recombinant DAD2 may help to clarify the precise molecular mechanisms through which this protein influences cell death pathways, potentially leading to new strategies for enhancing stress tolerance in crops.
Biotechnological Applications in Agriculture
The understanding of DAD2's role in stress tolerance and programmed cell death regulation opens possibilities for biotechnological applications aimed at improving crop resilience to environmental stressors. Given that DAD2 negatively regulates programmed cell death and reduces sensitivity to photooxidative stress, manipulation of DAD2 expression levels could potentially be used to develop crops with enhanced tolerance to light stress and delayed senescence . The antagonistic relationship between DAD2 and OXI1 suggests that targeted modification of this regulatory axis could provide a sophisticated approach to fine-tuning plant stress responses for specific agricultural contexts. The connection between DAD2 and hormone signaling pathways offers additional targets for intervention, potentially allowing for the development of crops with optimized defense responses that balance pathogen resistance with growth and yield . As climate change increases the frequency and severity of environmental stressors affecting agriculture, the insights gained from DAD2 research may become increasingly valuable for developing resilient crop varieties. Future research directions might explore how DAD2 function is influenced by different environmental conditions and how its activity can be optimized to enhance plant performance under specific stress scenarios.
Product Specs
Note: We will prioritize shipping the format that we have in stock. However, if you have any specific format requirements, please indicate them when placing your order, and we will prepare according to your needs.
Note: All our proteins are shipped with standard blue ice packs by default. If you require dry ice shipping, please inform us in advance, and 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 Arabidopsis thaliana DAD2 and what is its primary function?
Defender Against Cell Death 2 (DAD2) is a 115 amino acid protein in Arabidopsis thaliana that functions primarily as a strigolactone receptor involved in regulating plant development, particularly branching patterns . As the name suggests, DAD2 plays a critical role in cell death regulation pathways, somewhat similar to other cell death regulators in Arabidopsis such as ACD11 (Accelerated Cell Death 11) . When studying DAD2, it's important to understand that it functions within a network of proteins that collectively regulate programmed cell death and developmental processes in plants.
How is recombinant DAD2 protein typically produced for research applications?
Recombinant Arabidopsis thaliana DAD2 protein is most commonly expressed in E. coli expression systems with an N-terminal His-tag for purification purposes . The full-length protein (1-115 amino acids) can be produced with the following amino acid sequence: MVKSTSKDAQDLFHSLHSAYTATPTNLKIIDLYVCFAVFTALIQVAYMALVGSFPFNSFLSGVLSCIGTAVLAVCLRIQVNKENKEFKDLAPERAFADFVLCNLVLHLVIINFLG . For optimal stability after purification, the protein should be stored as aliquots at -20°C/-80°C in Tris/PBS-based buffer with 6% Trehalose at pH 8.0, and repeated freeze-thaw cycles should be avoided .
What are the key structural features of DAD2 that contribute to its function?
DAD2 is a member of the α/β-hydrolase fold protein family that functions as a strigolactone receptor. The protein's structure includes a binding pocket that accommodates strigolactone molecules, triggering conformational changes that initiate downstream signaling . When examining DAD2's function, researchers should consider that its activity depends on specific amino acid residues in the catalytic and binding regions. The protein contains several hydrophobic regions as indicated by its amino acid sequence, suggesting membrane association capabilities that may be crucial for its signaling function .
What genetic approaches are most effective for studying DAD2 function in Arabidopsis?
For studying DAD2 function, researchers have successfully employed several complementary genetic approaches. CRISPR-Cas9 gene editing has proven effective for creating knockout mutants, as demonstrated in studies with the Arabidopsis strigolactone receptor AtD14 . When designing such experiments, consider that complete knockout of genes involved in cell death pathways, like AGD2, can render embryos inviable, necessitating careful experimental design with conditional or tissue-specific knockouts .
Expression studies using promoter swaps are particularly valuable, as they allow investigation of the effects of altered expression patterns. For instance, expressing DAD2 from the constitutive CaMV 35S promoter in dad2 mutant petunia resulted in plants with intermediate phenotypes between wild-type and mutant, with greater height and leaf size but branch patterns similar to the mutant . This approach allows for nuanced analysis of gene function beyond simple presence/absence studies.
What are the recommended protocols for purifying and storing recombinant DAD2 protein?
For optimal purification of recombinant His-tagged DAD2 protein from E. coli, affinity chromatography using Ni-NTA resin is the preferred method, followed by size exclusion chromatography to achieve greater than 90% purity as determined by SDS-PAGE . After purification, the protein should be lyophilized or stored in a Tris/PBS-based buffer containing 6% Trehalose at pH 8.0 .
For reconstitution, centrifuge the lyophilized protein vial briefly before opening, then reconstitute in deionized sterile water to a concentration of 0.1-1.0 mg/mL, with the addition of 5-50% glycerol recommended for stability . Working aliquots should be stored at 4°C for no more than one week, while long-term storage requires -20°C/-80°C conditions with measures taken to avoid repeated freeze-thaw cycles that can compromise protein activity .
How can researchers effectively design reporter systems to study DAD2 signaling pathways?
To effectively monitor DAD2 signaling pathways, luciferase-based reporter systems have proven valuable, similar to the DLK2:LUC reporter used to study KAI2-dependent signaling . When designing such systems, select promoters of genes known to be regulated by the DAD2 pathway. The sensitivity of the assay can be enhanced by optimizing the promoter elements, potentially using synthetic promoters with concatemerized response elements identified from pathway-responsive genes .
For maximum specificity when studying strigolactone receptor functions, conduct experiments in appropriate genetic backgrounds to eliminate potential confounding factors. For example, using a d14 mutant background could exclude false positives from strigolactones when studying other signaling pathways . This approach ensures that the observed reporter activity is specifically due to the pathway of interest rather than parallel or overlapping signaling mechanisms.
How should researchers interpret phenotypic differences between DAD2 mutants and wild-type plants?
When analyzing phenotypic differences between DAD2 mutants and wild-type plants, researchers should consider multiple developmental parameters rather than focusing on a single trait. Studies have shown that alterations in DAD2 expression can affect plant height, leaf size, and branching patterns to different degrees . For example, expressing wild-type DAD2 from the CaMV 35S promoter in dad2 petunia mutants produced plants with greater height and leaf size (more wild-type-like) but branch numbers remained similar to the mutant .
It's crucial to examine these phenotypes under various environmental conditions, as the expression and function of cell death regulators can be context-dependent. Light conditions, in particular, have been shown to affect cell death execution in mutants of related pathways, such as acd11, where cell death induction by salicylic acid analogs occurred in light but not in dark conditions . Therefore, phenotypic analyses should include controlled variations in environmental parameters to fully understand DAD2 function.
What are the molecular markers and biochemical assays most informative for DAD2 activity?
For assessing DAD2 activity at the molecular level, several approaches are recommended. In vitro aminotransferase assays can be valuable for studying DAD2 function, similar to those used for the related proteins AGD2 and ALD1 . When conducting such assays, it's important to determine kinetic parameters to understand the directionality of the reaction, as homologous proteins can drive similar reactions in opposite directions .
Gene expression analysis of downstream targets provides another valuable molecular readout of DAD2 activity. This can be performed using qRT-PCR, RNA-seq, or cDNA microarray hybridization to monitor global transcriptional changes, similar to approaches used to study programmed cell death and defense activation in acd11 mutants . Key genes to monitor would include those involved in strigolactone signaling pathways and defense-related genes that accompany hypersensitive responses to pathogens.
How can researchers distinguish between direct and indirect effects of DAD2 in signaling pathways?
Distinguishing between direct and indirect effects of DAD2 in signaling pathways requires a multi-faceted approach. Epistatic analysis with mutants in related pathways is particularly informative, as demonstrated by studies showing that SA-dependent pathways require regulators such as PAD4 and EDS1 . When designing such experiments, create double mutants between dad2 and genes in potentially related pathways to establish dependency relationships.
Biochemical interaction studies using techniques such as co-immunoprecipitation, yeast two-hybrid assays, or bimolecular fluorescence complementation can identify direct protein interaction partners of DAD2. This is critical for constructing accurate signaling pathway models. Additionally, time-course experiments monitoring molecular and cellular changes following DAD2 activation can help establish the sequence of events and differentiate between early (likely direct) and late (potentially indirect) responses in the signaling cascade.
What is the relationship between DAD2 and other cell death regulators in Arabidopsis?
The relationship between DAD2 and other cell death regulators in Arabidopsis represents a complex network of interactions. DAD2 functions may overlap with other cell death regulators such as ACD11, whose mutation leads to lethal, recessive accelerated cell death with characteristics similar to animal apoptosis . When investigating these relationships, consider that cell death pathways in plants often involve salicylic acid (SA) as a key signaling molecule, with some pathways being SA-dependent and others SA-independent .
The role of reactive oxygen species (ROS) and nitric oxide (NO) should also be considered, as these molecules are important in hypersensitive response cell death . Inhibitor studies using compounds like diphenyleneiodonium (DPI), which reduces ROS production, have shown a decrease in apparent apoptosis in mutants with accelerated cell death phenotypes . Similar approaches could be valuable for dissecting DAD2's role in relation to these cellular signaling pathways.
How do evolutionary relationships inform DAD2 function across plant species?
DAD2 belongs to a broader family of strigolactone receptors with orthologs across plant species. Comparative studies between Arabidopsis thaliana and Petunia have revealed both conserved functions and species-specific differences . When analyzing such evolutionary relationships, researchers should consider that even closely related orthologs may exhibit differences in splicing patterns, as observed with the petunia DAD2 gene, which contains an intron that is efficiently cleaved in petunia but may be inappropriately recognized by the spliceosome in Arabidopsis .
Sequence analysis across species can identify conserved domains that likely represent functionally critical regions. Complementation experiments, where a DAD2 ortholog from one species is expressed in a dad2 mutant of another species, can reveal the degree of functional conservation. Such cross-species complementation experiments have shown that promoter selection is crucial when expressing genes across species boundaries, highlighting the importance of regulatory elements in gene function .
What are the methodological challenges in studying DAD2's role in strigolactone signaling and how can they be overcome?
Studying DAD2's role in strigolactone signaling presents several methodological challenges. One significant challenge is the low abundance of endogenous signaling molecules, similar to the difficulties faced in isolating karrikin-like compounds where active molecules were present at concentrations comparable to just 10 nM of the synthetic analog KAR2 . This necessitates large-scale growth of source material and sensitive detection methods. For comparison, the isolation of plant hormones like gibberellins and ABA historically required kilograms of plant material to isolate just milligrams of the compound .
Another challenge is the potential instability of these signaling molecules, particularly if they resemble strigolactones, which are known to hydrolyze in water . Researchers can address this through careful selection of solvents, extraction techniques, and separation methods. Developing more sensitive reporter assays, possibly using optimized synthetic promoters consisting of concatemerized response elements, could improve detection sensitivity . Additionally, using appropriate genetic backgrounds (such as d14 mutants when studying non-strigolactone pathways) can increase specificity by excluding false positives from related signaling molecules .
What controls should be included when studying recombinant DAD2 activity in vitro?
When studying recombinant DAD2 activity in vitro, several essential controls should be included to ensure reliable results. First, include enzymatically inactive DAD2 mutants, created by site-directed mutagenesis of catalytic residues, to distinguish between specific enzymatic activity and non-specific effects. These mutants should maintain proper folding but lack catalytic function, serving as ideal negative controls.
For protein quality control, perform thermal shift assays to verify proper folding of the recombinant protein, and size exclusion chromatography to confirm that the protein exists in the expected oligomeric state. When measuring DAD2's interaction with potential substrates or binding partners, include competition assays with known ligands to demonstrate specificity. Additionally, vary experimental conditions (pH, temperature, ionic strength) to determine optimal reaction parameters and ensure that observed activities reflect physiologically relevant processes rather than artifacts of the experimental system.
How can researchers resolve contradictory results when studying DAD2 function in different experimental systems?
Contradictory results when studying DAD2 across different experimental systems can arise from multiple factors. When encountering such discrepancies, first examine differences in experimental contexts, including expression systems, genetic backgrounds, and environmental conditions. For example, results from yeast systems, while useful for rapidly screening mutant genes, may not perfectly translate to plant systems due to differences in protein processing, post-translational modifications, or the absence of plant-specific interacting partners .
Genetic background effects are particularly important to consider, as demonstrated by the observation that expression of DAD2 from the CaMV 35S promoter in dad2 petunia resulted in plants with a mixture of wild-type and mutant-like traits rather than complete phenotypic rescue . This suggests that protein levels, tissue-specific expression patterns, and interactions with other genetic factors can all influence experimental outcomes. When possible, use multiple complementary approaches and genetic backgrounds to develop a more complete understanding of DAD2 function that reconciles apparently contradictory observations.
