Phylogeny, function, and evolution of the cupins, a structurally conserved, functionally diverse superfamily of proteins

Thiol dioxygenases: from structures to functions

Thiol oxidation to dioxygenated sulfinic acid is catalyzed by an enzyme family characterized by a cupin fold. These proteins act on free thiol-containing molecules to generate central metabolism precursors and signaling compounds in bacteria, fungi, and animal cells. In plants and animals, they also oxidize exposed N-cysteinyl residues, directing proteins to proteolysis. Enzyme kinetics, X-ray crystallography, and spectroscopy studies prompted the formulation and testing of hypotheses about the mechanism of action and the different substrate specificity of these enzymes. Concomitantly, the physiological role of thiol dioxygenation in prokaryotes and eukaryotes has been studied through genetic and physiological approaches. Further structural characterization is necessary to enable precise and safe manipulation of thiol dioxygenases (TDOs) for therapeutic, industrial, and agricultural applications.

Improved resolution of 3-mercaptopropionate dioxygenase active site provided by ENDOR spectroscopy offers insight into catalytic mechanism

3-mercaptopropionate (3MPA) dioxygenase (MDO) is a mononuclear nonheme iron enzyme that catalyzes the O2-dependent oxidation of thiol-bearing substrates to yield the corresponding sulfinic acid. MDO is a member of the cysteine dioxygenase family of small molecule thiol dioxygenases and thus shares a conserved sequence of active site residues (Serine-155, Histidine-157, and Tyrosine-159), collectively referred to as the SHY-motif. It has been demonstrated that these amino acids directly interact with the mononuclear Fe-site, influencing steady-state catalysis, catalytic efficiency, O2-binding, and substrate coordination. However, the underlying mechanism by which this is accomplished is poorly understood. Here, pulsed electron paramagnetic resonance spectroscopy [1H Mims electron nuclear double resonance spectroscopy] is applied to validate density functional theory computational models for the MDO Fe-site simultaneously coordinated by substrate and nitric oxide (NO), (3MPA/NO)-MDO. The enhanced resolution provided by electron nuclear double resonance spectroscopy allows for direct observation of Fe-bound substrate conformations and H-bond donation from Tyr159 to the Fe-bound NO ligand. Further inclusion of SHY-motif residues within the validated model reveals a distinct channel restricting movement of the Fe-bound NO-ligand. It has been argued that the iron-nitrosyl emulates the structure of potential Fe(III)-superoxide intermediates within the MDO catalytic cycle. While the merit of this assumption remains unconfirmed, the model reported here offers a framework to evaluate oxygen binding at the substrate-bound Fe-site and possible reaction mechanisms. It also underscores the significance of hydrogen bonding interactions within the enzymatic active site.

Protein3D: Enabling analysis and extraction of metal-containing sites from the Protein Data Bank with molSimplify

Metalloenzymes catalyze a wide range of chemical transformations, with the active site residues playing a key role in modulating chemical reactivity and selectivity. Unlike smaller synthetic catalysts, a metalloenzyme active site is embedded in a larger protein, which makes interrogation of electronic properties and geometric features with quantum mechanical calculations challenging. Here we implement the ability to fetch crystallographic structures from the Protein Data Bank and analyze the metal binding sites in the program molSimplify. We show the usefulness of the newly created protein3D class to extract the local environment around non-heme iron enzymes containing a two histidine motif and prepare 372 structures for quantum mechanical calculations. Our implementation of protein3D serves to expand the range of systems molSimplify can be used to analyze and will enable high-throughput study of metal-containing active sites in proteins.

RAF-like protein kinases mediate a deeply conserved, rapid auxin response

The plant-signaling molecule auxin triggers fast and slow cellular responses across land plants and algae. The nuclear auxin pathway mediates gene expression and controls growth and development in land plants, but this pathway is absent from algal sister groups. Several components of rapid responses have been identified in Arabidopsis, but it is unknown if these are part of a conserved mechanism. We recently identified a fast, proteome-wide phosphorylation response to auxin. Here, we show that this response occurs across 5 land plant and algal species and converges on a core group of shared targets. We found conserved rapid physiological responses to auxin in the same species and identified rapidly accelerated fibrosarcoma (RAF)-like protein kinases as central mediators of auxin-triggered phosphorylation across species. Genetic analysis connects this kinase to both auxin-triggered protein phosphorylation and rapid cellular response, thus identifying an ancient mechanism for fast auxin responses in the green lineage.

Identification and characterization of the cupin_1 domain-containing proteins in ma bamboo (Dendrocalamus latiflorus) and their potential role in rhizome sprouting

Cupin_1 domain-containing protein (CDP) family, which is a member of the cupin superfamily with the most diverse functions in plants, has been found to be involved in hormone pathways that are closely related to rhizome sprouting (RS), a vital form of asexual reproduction in plants. Ma bamboo is a typical clumping bamboo, which mainly reproduces by RS. In this study, we identified and characterized 53 Dendrocalamus latiflorus CDP genes and divided them into seven subfamilies. Comparing the genetic structures among subfamilies showed a relatively conserved gene structure within each subfamily, and the number of cupin_1 domains affected the conservation among D. latiflorus CDP genes. Gene collinearity results showed that segmental duplication and tandem duplication both contributed to the expansion of D. latiflorus CDP genes, and lineage-specific gene duplication was an important factor influencing the evolution of CDP genes. Expression patterns showed that CDP genes generally had higher expression levels in germinating underground buds, indicating that they might play important roles in promoting shoot sprouting. Transcription factor binding site prediction and co-expression network analysis indicated that D. latiflorus CDPs were regulated by a large number of transcription factors, and collectively participated in rhizome buds and shoot development. This study significantly provided new insights into the evolutionary patterns and molecular functions of CDP genes, and laid a foundation for further studying the regulatory mechanisms of plant rhizome sprouting.

Transient drought during flowering modifies the grain proteome of bread winter wheat

Drought is among the most limiting factors for sustainable agricultural production. Water shortage at the onset of flowering severely affects the quality and quantity of grain yield of bread wheat (Triticum aestivum). Herein, we measured oxidative stress and photosynthesis-related parameters upon applying transient drought on contrasting wheat cultivars at the flowering stage of ontogenesis. The sensitive cultivar (Darunok Podillia) showed ineffective water management and a more severe decline in photosynthesis. Apparently, the tolerant genotype (Odeska 267) used photorespiration to dissipate excessive light energy. The tolerant cultivar sooner induced superoxide dismutase and showed less inhibited photosynthesis. Such a protective effect resulted in less affected yield and spectrum of seed proteome. The tolerant cultivar had a more stable gluten profile, which defines bread-making quality, upon drought. Water deficit caused the accumulation of medically relevant proteins: (i) components of gluten in the sensitive cultivar and (ii) metabolic proteins in the tolerant cultivar. We propose specific proteins for further exploration as potential markers of drought tolerance for guiding efficient breeding: thaumatin-like protein, 14-3-3 protein, peroxiredoxins, peroxidase, FBD domain protein, and Ap2/ERF plus B3 domain protein.

Divergent structures and functions of the Cupin proteins in plants

Cupin superfamily proteins have extensive functions. Their members are not only involved in the development of plants but also responded to various stresses. Whereas, the research on the Cupin members has not attracted enough attention. In this article, we summarized the research progress on these family genes in recent years and explored their evolution, structural characteristics, and biological functions. The significance of members of the Cupin family in the development of plant cell walls, roots, leaves, flowers, fruits, and seeds and their role in stress response are highlighted. Simultaneously, the prospective application of Cupin protein in crop enhancement was introduced. Some members can enhance plant growth, development, and resistance to adversity, thereby increasing crop yield. It will be as a foundation for future effective crop research and breeding.

Comparative genomic analysis of the Dietzia genus: an insight into genomic diversity, and adaptation

Dietzia strains are widely distributed in the environment, presenting an opportunistic role, and some species have undetermined taxonomic characteristics. Here, we propose the existence of errors in the classification of species in this genus using comparative genomics. We performed ANI, dDDH, pangenome and genomic plasticity analyses better to elucidate the phylogenomic relationships between Dietzia strains. For this, we used 55 genomes of Dietzia downloaded from public databases that were combined with a newly sequenced. Sequence analysis of a phylogenetic tree based on genome similarity comparisons and dDDH, ANI analyses supported grouping different Dietzia species into four distinct groups. The pangenome analysis corroborated the classification of these groups, supporting the idea that some species of Dietzia could be reassigned in a possible classification into three distinct species, each containing less variability than that found within the global pangenome of all strains. Additionally, analysis of genomic plasticity based on groups containing Dietzia strains found differences in the presence and absence of symbiotic Islands and pathogenic islands related to their isolation site. We propose that the comparison of pangenome subsets together with phylogenomic approaches can be used as an alternative for the classification and differentiation of new species of the genus Dietzia.

Identification of genetic and biochemical mechanisms associated with heat shock and heat stress adaptation in grain amaranths

Heat stress is poised to become a major factor negatively affecting plant performance worldwide. In terms of world food security, increased ambient temperatures are poised to reduce yields in cereals and other economically important crops. Grain amaranths are known to be productive under poor and/or unfavorable growing conditions that significantly affect cereals and other crops. Several physiological and biochemical attributes have been recognized to contribute to this favorable property, including a high water-use efficiency and the activation of a carbon starvation response. This study reports the behavior of the three grain amaranth species to two different stress conditions: short-term exposure to heat shock (HS) conditions using young plants kept in a conditioned growth chamber or long-term cultivation under severe heat stress in greenhouse conditions. The latter involved exposing grain amaranth plants to daylight temperatures that hovered around 50°C, or above, for at least 4 h during the day and to higher than normal nocturnal temperatures for a complete growth cycle in the summer of 2022 in central Mexico. All grain amaranth species showed a high tolerance to HS, demonstrated by a high percentage of recovery after their return to optimal growing conditions. The tolerance observed coincided with increased expression levels of unknown function genes previously shown to be induced by other (a)biotic stress conditions. Included among them were genes coding for RNA-binding and RNA-editing proteins, respectively. HS tolerance was also in accordance with favorable changes in several biochemical parameters usually induced in plants in response to abiotic stresses. Conversely, exposure to a prolonged severe heat stress seriously affected the vegetative and reproductive development of all three grain amaranth species, which yielded little or no seed. The latter data suggested that the usually stress-tolerant grain amaranths are unable to overcome severe heat stress-related damage leading to reproductive failure.

FoCupin1, a Cupin_1 domain-containing protein, is necessary for the virulence of Fusarium oxysporum f. sp. cubense tropical race 4

Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) is an important soilborne fungal pathogen that causes the most devastating banana disease. Effectors secreted by microbes contribute to pathogen virulence on host plants in plant-microbe interactions. However, functions of Foc TR4 effectors remain largely unexplored. In this study, we characterized a novel cupin_1 domain-containing protein (FoCupin1) from Foc TR4. Sequence analysis indicated that the homologous proteins of FoCupin1 in phytopathogenic fungi were evolutionarily conserved. Furthermore, FoCupin1 could suppress BAX-mediated cell death and significantly downregulate the expression of defense-related genes in tobacco by using the Agrobacterium-mediated transient expression system. FoCupin1 was highly induced in the early stage of Foc TR4 infection. The deletion of FoCupin1 gene did not affect Foc TR4 growth and conidiation. However, FoCupin1 deletion significantly reduced Foc TR4 virulence on banana plants, which was further confirmed by biomass assay. The expression of the defense-related genes in banana was significantly induced after inoculation with FoCupin1 mutants. These results collectively indicate FoCupin1 is a putative effector protein that plays an essential role in Foc TR4 pathogenicity. These findings suggest a novel role for cupin_1 domain-containing proteins and deepen our understanding of effector-mediated Foc TR4 pathogenesis.

Characterization of a Secretory YML079-like Cupin Protein That Contributes to Sclerotinia sclerotiorum Pathogenicity

Sclerotinia sclerotiorum causes devastating diseases in many agriculturally important crops, including oilseed rape and sunflower. However, the mechanisms of Sclerotinia sclerotiorum pathogenesis remain poorly understood. In this study, we characterized a YML079-like cupin protein (SsYCP1) from Sclerotinia sclerotiorum. We showed that SsYCP1 is strongly expressed and secreted during Sclerotinia sclerotiorum infection. Sclerotinia sclerotiorum infection was promoted by SsYCP1 overexpression and inhibited by silencing this gene with synthetic double-stranded RNA. These results collectively indicate SsYCP1 as a putative effector protein that contributes to Sclerotinia sclerotiorum pathogenicity. These findings extend our understanding of effector-mediated Sclerotinia sclerotiorum pathogenesis and suggest a novel role for YML079-like cupin proteins in plant-pathogen interactions.

Identification of a Cupin Protein Gene Responsible for Pathogenicity, Phage Susceptibility and LPS Synthesis of Acidovorax citrulli

Bacteriophages infecting Acidovorax citrulli, the causal agent of bacterial fruit blotch, have been proven to be effective for the prevention and control of this disease. However, the occurrence of bacteriophage-resistant bacteria is one of hurdles in phage biocontrol and the understanding of phage resistance in this bacterium is an essential step. In this study, we aim to investigate possible phage resistance of A. citrulli and relationship between phage resistance and pathogenicity, and to isolate and characterize the genes involved in these phenomena. A phage-resistant and less-virulent mutant named as AC-17-G1 was isolated among 3,264 A. citrulli Tn5 mutants through serial spot assays and plaque assays followed by pathogenicity test using seed coating method. The mutant has the integrated Tn5 in the middle of a cupin protein gene. This mutant recovered its pathogenicity and phage sensitivity by complementation with corresponding wild-type gene. Site-directed mutation of this gene from wild-type by CRISPR/Cas9 system resulted in the loss of pathogenicity and acquisition of phage resistance. The growth of AC-17-G1 in King's B medium was much less than the wild-type, but the growth turned into normal in the medium supplemented with D-mannose 6-phosphate or D-fructose 6-phosphate indicating the cupin protein functions as a phosphomannos isomerase. Sodium dodecyl sulfa analysis of lipopolysaccharide (LPS) extracted from the mutant was smaller than that from wild-type. All these data suggest that the cupin protein is a phosphomannos isomerase involved in LPS synthesis, and LPS is an important determinant of pathogenicity and phage susceptibility of A. citrulli.

Genome-wide identification, classification, and expression analysis of the JmjC domain-containing histone demethylase gene family in birch

BACKGROUND

Histone methylation occurs primarily on lysine residues and requires a set of enzymes capable of reading, writing, and erasing to control its establishment and deletion, which is essential for maintaining chromatin structure and gene expression. Histone methylation and demethylation are contributed to plant growth and development, and are involved in adapting to environmental stresses. The JmjC domain-containing proteins are extensively studied for their function in histone lysine demethylation in plants, and play a critical role in sustaining histone methylation homeostasis.

RESULTS

In this study, a total of 21 JmjC domain-containing histone demethylase proteins (JHDMs) in birch were identified and classified into five subfamilies based on structural characteristics and phylogenetic relationships among Arabidopsis, rice, maize, and birch. Although the BpJMJ genes displayed significant schematic variation, their distribution on the chromosomes is relatively uniform. Additionally, the BpJMJ genes in birch have never experienced a tandem-duplication event proved by WGD analysis and were remaining underwent purifying selection (Ka/Ks < < 1). A typical JmjC domain was found in all BpJMJ genes, some of which have other essential domains for their functions. In the promoter regions of BpJMJ genes, cis-acting elements associated with hormone and abiotic stress responses were overrepresented. Under abiotic stresses, the transcriptome profile reveals two contrasting expression patterns within 21 BpJMJ genes. Furthermore, it was established that most BpJMJ genes had higher expression in young tissues under normal conditions, with BpJMJ06/16 having the highest expression in germinating seeds and participating in the regulation of BpGA3ox1/2 gene expression. Eventually, BpJMJ genes were found to directly interact with genes involved in the "intracellular membrane" in respond to cold stress.

CONCLUSIONS

The present study will provide a foundation for future experiments on histone demethylases in birch and a theoretical basis for epigenetic research on growth and development in response to abiotic stresses.

Extracellular sulfite is protective against reactive oxygen species and antibiotic stress in Shewanella oneidensis MR-1

In this study, we investigated the extracellular reactive sulfur species produced by Shewanella oneidensis MR-1 during growth. The results showed that sulfite is the major extracellular sulfur metabolite released to the growth medium under both aerobic and anaerobic growth conditions. Exogenous sulfite at physiological concentrations protected S. oneidensis MR-1 from hydrogen peroxide toxicity and enhanced tolerance to the beta-lactam antibiotics cefazolin, meropenem, doripenem and ertapenem. These findings suggest that the release of extracellular sulfite is a bacterial defence mechanism that plays a role in the mitigation of environmental stress.

Bacterial pathogens: threat or treat (a review on bioactive natural products from bacterial pathogens)

Covering: up to the second quarter of 2020 Threat or treat? While pathogenic bacteria pose significant threats, they also represent a huge reservoir of potential pharmaceuticals to treat various diseases. The alarming antimicrobial resistance crisis and the dwindling clinical pipeline urgently call for the discovery and development of new antibiotics. Pathogenic bacteria have an enormous potential for natural products drug discovery, yet they remained untapped and understudied. Herein, we review the specialised metabolites isolated from entomopathogenic, phytopathogenic, and human pathogenic bacteria with antibacterial and antifungal activities, highlighting those currently in pre-clinical trials or with potential for drug development. Selected unusual biosynthetic pathways, the key roles they play (where known) in various ecological niches are described. We also provide an overview of the mode of action (molecular target), activity, and minimum inhibitory concentration (MIC) towards bacteria and fungi. The exploitation of pathogenic bacteria as a rich source of antimicrobials, combined with the recent advances in genomics and natural products research methodology, could pave the way for a new golden age of antibiotic discovery. This review should serve as a compendium to communities of medicinal chemists, organic chemists, natural product chemists, biochemists, clinical researchers, and many others interested in the subject.

The dehydration- and ABA-inducible germin-like protein CpGLP1 from Craterostigma plantagineum has SOD activity and may contribute to cell wall integrity during desiccation

MAIN CONCLUSION

CpGLP1 belongs to the large group of germin-like proteins and comprises a cell wall-localized protein which has superoxide dismutase activity and may contribute towards ROS metabolism and cell wall folding during desiccation. The plant cell wall is a dynamic matrix and its plasticity is essential for cell growth and processing of environmental signals to cope with stresses. A few so-called resurrection plants like Craterostigma plantagineum survive desiccation by implementing protection mechanisms. In C. plantagineum, the cell wall shrinks and folds upon desiccation to avoid mechanical and oxidative damage which contributes to cell integrity. Despite the high toxic potential, ROS are important molecules for cell wall remodeling processes as they participate in enzymatic reactions and act as signaling molecules. Here we analyzed the C. plantagineum germin-like protein 1 (CpGLP1) to understand its contribution to cell wall folding and desiccation tolerance. The analysis of the CpGLP1 sequence showed that this protein does not fit into the current GLP classification and forms a new group within the Linderniaceae. CpGLP1 transcripts accumulate in leaves in response to dehydration and ABA, and mannitol treatments transiently induce CpGLP1 transcript accumulation supporting the participation of CpGLP1 in desiccation-related processes. CpGLP1 protein from cell wall protein extracts followed transcript accumulation and protein preparations from bacteria overexpressing CpGLP1 showed SOD activity. In agreement with cell wall localization, CpGLP1 interacts with pectins which have not been reported for GLP proteins. Our data support a role for CpGLP1 in the ROS metabolism related to the control of cell wall plasticity during desiccation in C. plantagineum.

Activity-based protein profiling of rice (Oryza sativa L.) bran serine hydrolases

Rice bran is an underutilized agricultural by-product with economic importance. The unique phytochemicals and fatty acid compositions of bran have been targeted for nutraceutical development. The endogenous lipases and hydrolases are responsible for the rapid deterioration of rice bran. Hence, we attempted to provide the first comprehensive profiling of active serine hydrolases (SHs) present in rice bran proteome by activity-based protein profiling (ABPP) strategy. The active site-directed fluorophosphonate probe (rhodamine and biotin-conjugated) was used for the detection and identification of active SHs. ABPP revealed 55 uncharacterized active-SHs and are representing five different known enzyme families. Based on motif and domain analyses, one of the uncharacterized and miss annotated SHs (Os12Ssp, storage protein) was selected for biochemical characterization by overexpressing in yeast. The purified recombinant protein authenticated the serine protease activity in time and protein-dependent studies. Os12Ssp exhibited the maximum activity at a pH between 7.0 and 8.0. The protease activity was inhibited by the covalent serine protease inhibitor, which suggests that the ABPP approach is indeed reliable than the sequence-based annotations. Collectively, the comprehensive knowledge generated from this study would be useful in expanding the current understanding of rice bran SHs and paves the way for better utilization/stabilization of rice bran.

The Apoplast: A Key Player in Plant Survival

The apoplast comprises the intercellular space, the cell walls, and the xylem. Important functions for the plant, such as nutrient and water transport, cellulose synthesis, and the synthesis of molecules involved in plant defense against both biotic and abiotic stresses, take place in it. The most important molecules are ROS, antioxidants, proteins, and hormones. Even though only a small quantity of ROS is localized within the apoplast, apoplastic ROS have an important role in plant development and plant responses to various stress conditions. In the apoplast, like in the intracellular cell compartments, a specific set of antioxidants can be found that can detoxify the different types of ROS produced in it. These scavenging ROS components confer stress tolerance and avoid cellular damage. Moreover, the production and accumulation of proteins and peptides in the apoplast take place in response to various stresses. Hormones are also present in the apoplast where they perform important functions. In addition, the apoplast is also the space where microbe-associated molecular Patterns (MAMPs) are secreted by pathogens. In summary, the diversity of molecules found in the apoplast highlights its importance in the survival of plant cells.

Shotgun proteomic analysis of quinoa seeds reveals novel lysine-rich seed storage globulins

Quinoa seeds have high protein content and an exceptional balance of amino acids, with higher contents of lysine, methionine and cysteine than common cereals. To date, only three globulins, all of which have a content of lysine mass that does not exceed 3.8%, have been identified in quinoa. To address the protein present in quinoa seeds, TCA/Acetone protein extraction was performed using four different quinoa seed genotypes with contrasting edaphoclimatic origins. Proteins were identified and analyzed using label-free shotgun proteomics followed by in silico analysis, using the three published quinoa genomes. This analysis allowed us to identify sixteen globulins, thirteen of which are novel: nine legumin-like proteins and seven vicilin-like proteins. Seven of the novel proteins contain 7.5% or more of lysine mass, justifying the high content of lysine repeatedly reported in quinoa seeds. No significant differences were found between the four genotypes here analyzed.

Shedding light on a Group IV (ECF11) alternative σ factor

This year marks the 50th anniversary of the discovery of σ70 as a protein factor that was needed for bacterial RNA polymerase to accurately transcribe a promoter in vitro. It was 25 years later that the Group IV alternative σs were described as a distinct family of proteins related to σ70 . In the intervening time, there has been an ever-growing list of Group IV σs, numbers of genes they transcribe, insight into the diverse suite of processes they control, and appreciation for their impact on bacterial lifestyles. This work summarizes knowledge of the Rhodobacter sphaeroides σE -ChrR pair, a member of the ECF11 subfamily of Group IV alternative σs, in protecting cells from the reactive oxygen species, singlet oxygen. It describes lessons learned from analyzing ChrR, a zinc-dependent anti-σ factor, that are generally applicable to Group IV σs and relevant to the response to single oxygen. This MicroReview also illustrates insights into stress responses in this and other bacteria that have been acquired by analyzing or modeling the activity of the σE -ChrR across the bacterial phylogeny.

Isolation and Assays of Bacterial Dimethylsulfoniopropionate Lyases

The organosulfur metabolite dimethylsulfoniopropionate (DMSP) and its enzymatic breakdown product dimethyl sulfide (DMS) have important implications in the global sulfur cycle and in marine microbial food webs. Enormous amounts of DMSP are produced in marine environments where microbial communities import and catabolize it via either the demethylation or the cleavage pathways. The enzymes that cleave DMSP are termed "DMSP lyases" and generate acrylate or hydroxypropionate, and ~10⁷tons of DMS annually. An important environmental factor affecting DMS generation by the DMSP lyases is the availability of metal ions as these enzymes use various cofactors for catalysis. This chapter summarizes advances on bacterial DMSP catabolism, with an emphasis on various biochemical methods employed for the isolation and characterization of bacterial DMSP lyases. Strategies are presented for the purification of DMSP lyases expressed in bacterial cells. Specific conditions for the efficient isolation of apoproteins in Escherichia coli are detailed. DMSP cleavage is effectively inferred, utilizing the described HPLC-based acrylate detection assay. Finally, substrate and metal binding interactions are examined using fluorescence and UV-visible assays. Together, these methods are rapid and well suited for the biochemical and structural characterization of DMSP lyases and in the assessment of uncharacterized DMSP catabolic enzymes, and new metalloenzymes in general.

The Effect of Plant Genotype, Growth Stage, and Mycosphaerella graminicola Strains on the Efficiency and Durability of Wheat-Induced Resistance by Paenibacillus sp. Strain B2

Plant-growth-promoting rhizobacteria are known as potential biofertilizers and plant-resistance inducers. The current work aims to study the durability of the resistance induced as a response to the inoculation of wheat grains with Paenibacillus sp. strain B2 (PB2) and its influence by plant genotype, growth stage, and Mycosphaerella graminicola strain (the causal agent of Septoria tritici blotch or STB). The results of the plate-counting method showed that PB2 has high potential for wheat-root external colonization [>106 colony-forming unit (CFU)/g of root], and the quantitative real-time polymerase chain reaction (qPCR) analysis demonstrated its internal root-colonization capacity on all tested cultivars. However, the colonization seems to be dependent on wheat-growth stage. The durability of PB2-induced resistance (PB2-IR) was tested at the 3-leaf, tillering, and flag-leaf-growth stages. Additionally, the results showed that the PB2-IR is durable and able to protect the flag leaf, the most important leaf layer during grain fill. It conferred a high protection efficiency (55-94%) against four virulent strains of M. graminicola and over 11 wheat cultivars with different resistance levels to STB. Although, PB2-IR is dependent on M. graminicola strains, wheat genotypes and growth stages, its efficiency, under field conditions, at protecting the last wheat-leaf layers was not an influence. However, it showed 71-79% of protection and reached 81-94% in association with half of the recommended dose of Cherokee® fungicide. This may be explained using laboratory results by its direct impact on M. graminicola strains in these leaf layers and by the indirect reduction of the inoculum coming from leaves infected during the earlier growth stages. Gene expression results showed that PB2-IR is correlated to upregulation of genes involved in defense and cell rescue and a priming effect in the basal defense, jasmonic acid signaling, phenylpropanoids and phytoalexins, and reactive oxygen species gene markers. To conclude, PB2 induces a high and durable resistance against M. graminicola under controlled and field conditions. The PB2-IR is a pathogen strain and is plant-growth-stage and genotype dependent. These results highlight the importance of taking into consideration these factors so as to avoid losing the effectiveness of induced resistance under field conditions.

A cupin domain is involved in α-amylase inhibitory activity

Proteinaceous α-amylase inhibitors have specialized activities that make some strong inhibition of α-amylases. New α-amylase inhibitors continue to be discovered so far. A proteinaceous α-amylase inhibitor CL-AI was isolated and identified from chickpea seeds. CL-AI, encoded by Q9SMJ4, was a storage legumin precursor containing one α-chain and one β-chain, and each chain possessed a same conserved cupin domain. Amino acid mutation and deficiency of cupin domain would lead to loss of α-amylase inhibitory activity, indicating that it was essential for inhibitory activity. CL-AI(α + β) in its single stranded state in vivo had inhibitory activity. After it was processed into one α-chain and one β-chain, the two chains were connected to each other via disulfide bond, which would cover the cupin domains and lead to the loss of inhibitory activity. The CL-AI(α + β), α-chain and β-chain could inhibit various α-amylases and delay the seed germination of wheat, rice and maize as well as the growth and development of potato beetle larva. Two cupin proteins, Glycinin G1 in soybean and Glutelinin in rice were also found to have inhibitory activity. Our results indicated that the cupin domain is involved in α-amylase inhibitory activity and the proteins with a cupin domain may be a new kind of proteinaceous α-amylase inhibitor.

Pirin: A novel redox-sensitive modulator of primary and secondary metabolism in Streptomyces

Pirins are evolutionarily conserved iron-containing proteins that are found in all kingdoms of life, and have been implicated in diverse molecular processes, mostly associated with cellular stress. In the present study, we started from the evidence that the insertional inactivation of pirin-like gene SAM23877_RS18305 (pirA) by ΦC31 Att/Int system-based vectors in spiramycin-producing strain Streptomyces ambofaciens ATCC 23877 resulted in marked effects on central carbon and energy metabolism gene expression, high sensitivity to oxidative injury and repression of polyketide antibiotic production. By using integrated transcriptomic, proteomic and metabolite profiling, together with genetic complementation, we here show that most of these effects could be traced to the inability of the pirA-defective strain to modulate beta-oxidation pathway, leading to an unbalanced supply of precursor monomers for polyketide biosynthesis. Indeed, in silico protein-protein interaction modeling and in vitro experimental validation allowed us to demonstrate that PirA is a novel redox-sensitive negative modulator of very long-chain acyl-CoA dehydrogenase, which catalyzes the first committed step of the beta-oxidation pathway.

Enrichment and Identification of the Most Abundant Zinc Binding Proteins in Developing Barley Grains by Zinc-IMAC Capture and Nano LC-MS/MS

Background: Zinc accumulates in the embryo, aleurone, and subaleurone layers at different amounts in cereal grains. Our hypothesis is that zinc could be stored bound, not only to low MW metabolites/proteins, but also to high MW proteins as well. Methods: In order to identify the most abundant zinc binding proteins in different grain tissues, we microdissected barley grains into (1) seed coats; (2) aleurone/subaleurone; (3) embryo; and (4) endosperm. Initial screening for putative zinc binding proteins from the different tissue types was performed by fractionating proteins according to solubility (Osborne fractionation), and resolving those via Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) followed by polyvinylidene fluoride (PVDF) membrane blotting and dithizone staining. Selected protein fractions were subjected to Zn²⁺-immobilized metal ion affinity chromatography, and the captured proteins were identified using nanoscale liquid chromatography coupled to tandem mass spectrometry (nanoLC-MS/MS). Results: In the endosperm, the most abundant zinc binding proteins were the storage protein B-hordeins, gamma-, and D-hordeins, while in the embryo, 7S globulins storage proteins exhibited zinc binding. In the aleurone/subaleurone, zinc affinity captured proteins were late abundant embryogenesis proteins, dehydrins, many isoforms of non-specific lipid transfer proteins, and alpha amylase trypsin inhibitor. Conclusions: We have shown evidence that abundant barley grain proteins have been captured by Zn-IMAC, and their zinc binding properties in relationship to the possibility of zinc storage is discussed.

Comparative Proteomic Analysis of Paulownia fortunei Response to Phytoplasma Infection with Dimethyl Sulfate Treatment

Paulownia fortunei is a widely cultivated economic forest tree species that is susceptible to infection with phytoplasma, resulting in Paulownia witches' broom (PaWB) disease. Diseased P. fortunei is characterized by stunted growth, witches' broom, shortened internodes, and etiolated and smaller leaves. To understand the molecular mechanism of its pathogenesis, we applied isobaric tags for relative and absolute quantitation (iTRAQ) and liquid chromatography coupled with tandem mass spectrometry approaches to study changes in the proteomes of healthy P. fortunei, PaWB-infected P. fortunei, and PaWB-infected P. fortunei treated with 15 mg·L⁻¹ or 75 mg·L⁻¹ dimethyl sulfate. We identified 2969 proteins and 104 and 32 differentially abundant proteins that were phytoplasma infection responsive and dimethyl sulfate responsive, respectively. Based on our analysis of the different proteomes, 27 PaWB-related proteins were identified. The protein-protein interactions of these 27 proteins were analyzed and classified into four groups (photosynthesis-related, energy-related, ribosome-related, and individual proteins). These PaWB-related proteins may help in developing a deeper understanding of how PaWB affects the morphological characteristics of P. fortunei and further establish the mechanisms involved in the response of P. fortunei to phytoplasma.

Marine-Derived Biocatalysts: Importance, Accessing, and Application in Aromatic Pollutant Bioremediation

The aim of the present review is to highlight the potential use of marine biocatalysts (whole cells or enzymes) as an alternative bioprocess for the degradation of aromatic pollutants. Firstly, information about the characteristics of the still underexplored marine environment and the available scientific tools used to access novel marine-derived biocatalysts is provided. Marine-derived enzymes, such as dioxygenases and dehalogenases, and the involved catalytic mechanisms for the degradation of aromatic and halogenated compounds, are presented, with the purpose of underpinning their potential use in bioremediation. Emphasis is given on persistent organic pollutants (POPs) that are organic compounds with significant impact on health and environment due to their resistance in degradation. POPs bioaccumulate mainly in the fatty tissue of living organisms, therefore current efforts are mostly focused on the restriction of their use and production, since their removal is still unclear. A brief description of the guidelines and criteria that render a pollutant POP is given, as well as their potential biodegradation by marine microorganisms by surveying recent developments in this rather unexplored field.

Oxygen activation by mononuclear nonheme iron dioxygenases involved in the degradation of aromatics

Molecular oxygen is utilized in numerous metabolic pathways fundamental for life. Mononuclear nonheme iron-dependent oxygenase enzymes are well known for their involvement in some of these pathways, activating O₂ so that oxygen atoms can be incorporated into their primary substrates. These reactions often initiate pathways that allow organisms to use stable organic molecules as sources of carbon and energy for growth. From the myriad of reactions in which these enzymes are involved, this perspective recounts the general mechanisms of aromatic dihydroxylation and oxidative ring cleavage, both of which are ubiquitous chemical reactions found in life-sustaining processes. The organic substrate provides all four electrons required for oxygen activation and insertion in the reactions mediated by extradiol and intradiol ring-cleaving catechol dioxygenases. In contrast, two of the electrons are provided by NADH in the cis-dihydroxylation mechanism of Rieske dioxygenases. The catalytic nonheme Fe center, with the aid of active site residues, facilitates these electron transfers to O₂ as key elements of the activation processes. This review discusses some general questions for the catalytic strategies of oxygen activation and insertion into aromatic compounds employed by mononuclear nonheme iron-dependent dioxygenases. These include: (1) how oxygen is activated, (2) whether there are common intermediates before oxygen transfer to the aromatic substrate, and (3) are these key intermediates unique to mononuclear nonheme iron dioxygenases?

Discovery of a Chemical Probe Bisamide (CCT251236): An Orally Bioavailable Efficacious Pirin Ligand from a Heat Shock Transcription Factor 1 (HSF1) Phenotypic Screen

Phenotypic screens, which focus on measuring and quantifying discrete cellular changes rather than affinity for individual recombinant proteins, have recently attracted renewed interest as an efficient strategy for drug discovery. In this article, we describe the discovery of a new chemical probe, bisamide (CCT251236), identified using an unbiased phenotypic screen to detect inhibitors of the HSF1 stress pathway. The chemical probe is orally bioavailable and displays efficacy in a human ovarian carcinoma xenograft model. By developing cell-based SAR and using chemical proteomics, we identified pirin as a high affinity molecular target, which was confirmed by SPR and crystallography.

Narrow-Leafed Lupin (Lupinus angustifolius) β1- and β6-Conglutin Proteins Exhibit Antifungal Activity, Protecting Plants against Necrotrophic Pathogen Induced Damage from Sclerotinia sclerotiorum and Phytophthora nicotianae

Vicilins (7S globulins) are seed storage proteins and constitute the main protein family in legume seeds, particularly in narrow-leafed lupin (Lupinus angustifolius L.; NLL), where seven vicilin genes, called β1- to β7-conglutin have been identified. Vicilins are involved in germination processes supplying amino acids for seedling growth and plant development, as well as in some cases roles in plant defense and protection against pathogens. The roles of NLL β-conglutins in plant defense are unknown. Here the potential role of five NLL β-conglutin family members in protection against necrotrophic fungal pathogens was investigated and it was demonstrated that recombinant purified 6xHis-tagged β1- and β6-conglutin proteins exhibited the strongest in vitro growth inhibitory activity against a range of necrotrophic fungal pathogens compared to β2, β3, and β4 conglutins. To examine activity in vivo, two representative necrotrophic pathogens, the fungus Sclerotinia sclerotiorum and oomycete Phytophthora nicotianae were used. Transient expression of β1- and β6-conglutin proteins in Nicotiana benthamiana leaves demonstrated in vivo growth suppression of both of these pathogens, resulting in low percentages of hyphal growth and elongation in comparison to control treated leaves. Cellular studies using β1- and β6-GFP fusion proteins showed these conglutins localized to the cell surface including plasmodesmata. Analysis of cellular death following S. sclerotiorum or P. nicotianae revealed both β1- and β6-conglutins suppressed pathogen induced cell death in planta and prevented pathogen induced suppression of the plant oxidative burst as determined by protein oxidation in infected compared to mock-inoculated leaves.

New Mechanistic Insight from Substrate- and Product-Bound Structures of the Metal-Dependent Dimethylsulfoniopropionate Lyase DddQ

The marine microbial catabolism of dimethylsulfoniopropionate (DMSP) by the lyase pathway liberates ∼300 million tons of dimethyl sulfide (DMS) per year, which plays a major role in the biogeochemical cycling of sulfur. Recent biochemical and structural studies of some DMSP lyases, including DddQ, reveal the importance of divalent transition metal ions in assisting DMSP cleavage. While DddQ is believed to be zinc-dependent primarily on the basis of structural studies, excess zinc inhibits the enzyme. We examine the importance of iron in regulating the DMSP β-elimination reaction catalyzed by DddQ as our as-isolated purple-colored enzyme possesses ∼0.5 Fe/subunit. The UV-visible spectrum exhibited a feature at 550 nm, consistent with a tyrosinate-Fe(III) ligand-to-metal charge transfer transition. Incubation of as-isolated DddQ with added iron increases the intensity of the 550 nm peak, whereas addition of dithionite causes a bleaching as Fe(III) is reduced. Both the Fe(III) oxidized and Fe(II) reduced species are active, with similar k_cat values and 2-fold differences in their K_m values for DMSP. The slow turnover of Fe(III)-bound DddQ allowed us to capture a substrate-bound form of the enzyme. Our DMSP-Fe(III)-DddQ structure reveals conformational changes associated with substrate binding and shows that DMSP is positioned optimally to bind iron and is in the proximity of Tyr 120 that acts as a Lewis base to initiate catalysis. The structures of Tris-, DMSP-, and acrylate-bound forms of Fe(III)-DddQ reported here illustrate various states of the enzyme along the reaction pathway. These results provide new insights into DMSP lyase catalysis and have broader significance for understanding the mechanism of oceanic DMS production.

Do Cupins Have a Function Beyond Being Seed Storage Proteins?

Plants continue to flourish around the site of the Chernobyl Nuclear Power Plant disaster. The ability of plants to transcend the radio-contaminated environment was not anticipated and is not well understood. The aim of this study was to evaluate the proteome of flax (Linum usitatissimum L.) during seed filling by plants grown for a third generation near Chernobyl. For this purpose, seeds were harvested at 2, 4, and 6 weeks after flowering and at maturity, from plants grown in either non-radioactive or radio-contaminated experimental fields. Total proteins were extracted and the two-dimensional gel electrophoresis (2-DE) patterns analyzed. This approach established paired abundance profiles for 130 2-DE spots, e.g., profiles for the same spot across seed filling in non-radioactive and radio-contaminated experimental fields. Based on Analysis of Variance (ANOVA) followed by sequential Bonferroni correction, eight of the paired abundance profiles were discordant. Results from tandem mass spectrometry show that four 2-DE spots are discordant because they contain fragments of the cupin superfamily-proteins. Most of the fragments were derived from the N-terminal half of native cupins. Revisiting previously published data, it was found that cupin-fragments were also involved with discordance in paired abundance profiles of second generation flax seeds. Based on these observations we present an updated working model for the growth and reproductive success of flax in a radio-contaminated Chernobyl environment. This model suggests that the increased abundance of cupin fragments or isoforms and monomers contributes to the successful growth and reproduction of flax in a radio-contaminated environment.

Fungal oxalate decarboxylase activity contributes to Sclerotinia sclerotiorum early infection by affecting both compound appressoria development and function

Sclerotinia sclerotiorum pathogenesis requires the accumulation of high levels of oxalic acid (OA). To better understand the factors affecting OA accumulation, two putative oxalate decarboxylase (OxDC) genes (Ss-odc1 and Ss-odc2) were characterized. Ss-odc1 transcripts exhibited significant accumulation in vegetative hyphae, apothecia, early stages of compound appressorium development and during plant colonization. Ss-odc2 transcripts, in contrast, accumulated significantly only during mid to late stages of compound appressorium development. Neither gene was induced by low pH or exogenous OA in vegetative hyphae. A loss-of-function mutant for Ss-odc1 (Δss-odc1) showed wild-type growth, morphogenesis and virulence, and was not characterized further. Δss-odc2 mutants hyperaccumulated OA in vitro, were less efficient at compound appressorium differentiation and exhibited a virulence defect which could be fully bypassed by wounding the host plant prior to inoculation. All Δss-odc2 phenotypes were restored to the wild-type by ectopic complementation. An S. sclerotiorum strain overexpressing Ss-odc2 exhibited strong OxDC, but no oxalate oxidase activity. Increasing inoculum nutrient levels increased compound appressorium development, but not penetration efficiency, of Δss-odc2 mutants. Together, these results demonstrate differing roles for S. sclerotiorum OxDCs, with Odc2 playing a significant role in host infection related to compound appressorium formation and function.

Immobilization of Bacillus subtilis oxalate decarboxylase on a Zn-IMAC resin

Oxalate decarboxylase, a bicupin enzyme coordinating two essential manganese ions per subunit, catalyzes the decomposition of oxalate into carbon dioxide and formate in the presence of oxygen. Current efforts to elucidate its catalytic mechanism are focused on EPR studies of the Mn. We report on a new immobilization strategy linking the enzyme's N-terminal His₆-tag to a Zn-loaded immobilized metal affinity resin. Activity is lowered somewhat due to the expected crowding effect. High-field EPR spectra of free and immobilized enzyme show that the resin affects the coordination environment of the active site Mn ions only minimally. The immobilized preparation was used to study the effect of varying pH on the same sample. Repeated freeze-thaw cycles lead to break down of the resin beads and some enzyme loss from the sample. However, the EPR signal increases due to higher packing efficiency on the sample column.

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Immobilization of Oxalate decarboxylase on Zn-IMAC resin.

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Overall K_M is unaffected after immobilization.

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Immobilized enzyme exhibits lower overall activity due to crowding on the resin.

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High-field EPR confirms minimal perturbations of manganese sites due to immobilization.

Crystal structure of PnpCD, a two-subunit hydroquinone 1,2-dioxygenase, reveals a novel structural class of Fe2+-dependent dioxygenases

Aerobic microorganisms have evolved a variety of pathways to degrade aromatic and heterocyclic compounds. However, only several classes of oxygenolytic fission reaction have been identified for the critical ring cleavage dioxygenases. Among them, the most well studied dioxygenases proceed via catecholic intermediates, followed by noncatecholic hydroxy-substituted aromatic carboxylic acids. Therefore, the recently reported hydroquinone 1,2-dioxygenases add to the diversity of ring cleavage reactions. Two-subunit hydroquinone 1,2-dioxygenase PnpCD, the key enzyme in the hydroquinone pathway of para-nitrophenol degradation, catalyzes the ring cleavage of hydroquinone to γ-hydroxymuconic semialdehyde. Here, we report three PnpCD structures, named apo-PnpCD, PnpCD-Fe(3+), and PnpCD-Cd(2+)-HBN (substrate analog hydroxyenzonitrile), respectively. Structural analysis showed that both the PnpC and the C-terminal domains of PnpD comprise a conserved cupin fold, whereas PnpC cannot form a competent metal binding pocket as can PnpD cupin. Four residues of PnpD (His-256, Asn-258, Glu-262, and His-303) were observed to coordinate the iron ion. The Asn-258 coordination is particularly interesting because this coordinating residue has never been observed in the homologous cupin structures of PnpCD. Asn-258 is proposed to play a pivotal role in binding the iron prior to the enzymatic reaction, but it might lose coordination to the iron when the reaction begins. PnpD also consists of an intriguing N-terminal domain that might have functions other than nucleic acid binding in its structural homologs. In summary, PnpCD has no apparent evolutionary relationship with other iron-dependent dioxygenases and therefore defines a new structural class. The study of PnpCD might add to the understanding of the ring cleavage of dioxygenases.

A gene co-expression network predicts functional genes controlling the re-establishment of desiccation tolerance in germinated Arabidopsis thaliana seeds

During re-establishment of desiccation tolerance (DT), early events promote initial protection and growth arrest, while late events promote stress adaptation and contribute to survival in the dry state. Mature seeds of Arabidopsis thaliana are desiccation tolerant, but they lose desiccation tolerance (DT) while progressing to germination. Yet, there is a small developmental window during which DT can be rescued by treatment with abscisic acid (ABA). To gain temporal resolution and identify relevant genes in this process, data from a time series of microarrays were used to build a gene co-expression network. The network has two regions, namely early response (ER) and late response (LR). Genes in the ER region are related to biological processes, such as dormancy, acquisition of DT and drought, amplification of signals, growth arrest and induction of protection mechanisms (such as LEA proteins). Genes in the LR region lead to inhibition of photosynthesis and primary metabolism, promote adaptation to stress conditions and contribute to seed longevity. Phenotyping of 12 hubs in relation to re-establishment of DT with T-DNA insertion lines indicated a significant increase in the ability to re-establish DT compared with the wild-type in the lines cbsx4, at3g53040 and at4g25580, suggesting the operation of redundant and compensatory mechanisms. Moreover, we show that re-establishment of DT by polyethylene glycol and ABA occurs through partially overlapping mechanisms. Our data confirm that co-expression network analysis is a valid approach to examine data from time series of transcriptome analysis, as it provides promising insights into biologically relevant relations that help to generate new information about the roles of certain genes for DT.

Transcriptomic changes during maize roots development responsive to Cadmium (Cd) pollution using comparative RNAseq-based approach

The heavy metal cadmium (Cd), acts as a widespread environmental contaminant, which has shown to adversely affect human health, food safety and ecosystem safety in recent years. However, research on how plant respond to various kinds of heavy metal stress is scarcely reported, especially for understanding of complex molecular regulatory mechanisms and elucidating the gene networks of plant respond to Cd stress. Here, transcriptomic changes during Mo17 and B73 seedlings development responsive to Cd pollution were investigated and comparative RNAseq-based approach in both genotypes were performed. 115 differential expression genes (DEGs) with significant alteration in expression were found co-modulated in both genotypes during the maize seedling development; of those, most of DGEs were found comprised of stress and defense responses proteins, transporters, as well as transcription factors, such as thaumatin-like protein, ZmOPR2 and ZmOPR5. More interestingly, genotype-specific transcriptional factors changes induced by Cd stress were found contributed to the regulatory mechanism of Cd sensitivity in both different genotypes. Moreover, 12 co-expression modules associated with specific biological processes or pathways (M1 to M12) were identified by consensus co-expression network. These results will expand our understanding of complex molecular mechanism of response and defense to Cd exposure in maize seedling roots.

The crystal structure of Helicobacter pylori HP1029 highlights the functional diversity of the sialic acid-related DUF386 family

The proteins of the YhcH/YjgK/YiaL (DUF386) family have been implicated in the bacterial metabolism of host-derived sialic acids and biofilm formation, although their precise biochemical function remains enigmatic. We present here the crystal structure of protein HP1029 from Helicobacter pylori. The protein is a homodimer, in which each monomer comprises a molecular core formed by 12 antiparallel β-strands arranged in two β-sheets flanked by helices. The sandwich formed by the sheets assumes the shape of a funnel opened at one end, with a zinc ion present at the bottom of the funnel. The crystal structure unequivocally shows that HP1029 belongs to the DUF386 family. Although no bioinformatics evidence has been found for sialic acid catabolism in H. pylori, the genomic context of HP1029 in Helicobacter and related organisms suggests a possible role in the metabolism of bacterial surface saccharides, such as pseudaminic acid and its derivatives.

Biochemical, Kinetic, and Spectroscopic Characterization of Ruegeria pomeroyi DddW--A Mononuclear Iron-Dependent DMSP Lyase

The osmolyte dimethylsulfoniopropionate (DMSP) is a key nutrient in marine environments and its catabolism by bacteria through enzymes known as DMSP lyases generates dimethylsulfide (DMS), a gas of importance in climate regulation, the sulfur cycle, and signaling to higher organisms. Despite the environmental significance of DMSP lyases, little is known about how they function at the mechanistic level. In this study we biochemically characterize DddW, a DMSP lyase from the model roseobacter Ruegeria pomeroyi DSS-3. DddW is a 16.9 kDa enzyme that contains a C-terminal cupin domain and liberates acrylate, a proton, and DMS from the DMSP substrate. Our studies show that as-purified DddW is a metalloenzyme, like the DddQ and DddP DMSP lyases, but contains an iron cofactor. The metal cofactor is essential for DddW DMSP lyase activity since addition of the metal chelator EDTA abolishes its enzymatic activity, as do substitution mutations of key metal-binding residues in the cupin motif (His81, His83, Glu87, and His121). Measurements of metal binding affinity and catalytic activity indicate that Fe(II) is most likely the preferred catalytic metal ion with a nanomolar binding affinity. Stoichiometry studies suggest DddW requires one Fe(II) per monomer. Electronic absorption and electron paramagnetic resonance (EPR) studies show an interaction between NO and Fe(II)-DddW, with NO binding to the EPR silent Fe(II) site giving rise to an EPR active species (g = 4.29, 3.95, 2.00). The change in the rhombicity of the EPR signal is observed in the presence of DMSP, indicating that substrate binds to the iron site without displacing bound NO. This work provides insight into the mechanism of DMSP cleavage catalyzed by DddW.

Bioinformatic approach in the identification of arabidopsis gene homologous in amaranthus

Bioinfomatics offers an efficient tool for molecular genetics applications and sequence homology search algorithms became an inevitable part for many different research strategies. Appropriate managing of known data that are stored in public available databases can be used in many ways in the research. Here, we report the identification of RmlC-like cupins superfamily protein DNA sequence than is known in Arabidopsis genome for the Amaranthus - plant specie where this sequence was still not sequenced. A BLAST based approach was used to identify the homologous sequences in the nucleotide database and to find suitable parts of the Arabidopsis sequence were primers can be designed. In total, 64 hits were found in nucleotide database for Arabidopsis RmlC-like cupins sequence. A query cover ranged from 10% up to the 100% among RmlC-like cupins nucleotides and its homologues that are actually stored in public nucleotide databases. The most conserved region was identified for matches that posses nucleotides in the range of 1506 up to the 1925 bp of RmlC-like cupins DNA sequence stored in the database. The in silico approach was subsequently used in PCR analysis where the specifity of designed primers was approved. A unique, 250 bp long fragment was obtained for Amaranthus cruentus and a hybride Amaranthus hypochondriacus x hybridus in our analysis. Bioinformatic based analysis of unknown parts of the plant genomes as showed in this study is a very good additional tool in PCR based analysis of plant variability. This approach is suitable in the case for plants, where concrete genomic data are still missing for the appropriate genes, as was demonstrated for Amaranthus. 

In vitro and in vivo evidence for oxalate oxidase activity of a germin-like protein from azalea

Germins and germin-like proteins (GLPs) comprise large families of extracellular plant glycoproteins that are structurally similar, yet they have been reported to have distinct biochemical activities: oxalate oxidase and superoxide dismutase activities, respectively. We expressed an azalea GLP (RmGLP2) in cultured cells of tobacco, and determined that the extracellular protein fraction and the recombinant RmGLP2 protein purified from these cells catalyzed the oxidation of oxalate. Notably, this activity is purportedly restricted to germin and has not been demonstrated for a GLP. Although the specific activity of the purified RmGLP2 protein was low compared with that of a previously characterized barley germin/oxalate oxidase, tobacco cells expressing RmGLP2 exhibited significantly reduced oxalate levels. Thus, RmGLP2 represents the first reported GLP with oxalate oxidase activity.

Observation of superoxide production during catalysis of Bacillus subtilis oxalate decarboxylase at pH 4

This contribution describes the trapping of the hydroperoxyl radical at a pH of 4 during turnover of wild-type oxalate decarboxylase and its T165V mutant using the spin-trap BMPO. Radicals were detected and identified by a combination of EPR and mass spectrometry. Superoxide, or its conjugate acid, the hydroperoxyl radical, is expected as an intermediate in the decarboxylation and oxidation reactions of the oxalate monoanion, both of which are promoted by oxalate decarboxylase. Another intermediate, the carbon dioxide radical anion was also observed. The quantitative yields of superoxide trapping are similar in the wild type and the mutant while it is significantly different for the trapping of the carbon dioxide radical anion. This suggests that the two radicals are released from different sites of the protein.

Gel-free quantitative proteomic approach to identify cotyledon proteins in soybean under flooding stress

Flooding stress causes growth inhibition and ultimately death in most crop species by limiting of energy production. To better understand plant responses to flooding stress, here, flooding-responsive proteins in the cotyledons of soybean were identified using a gel-free quantitative proteomic approach. One hundred forty six proteins were commonly observed in both control and flooding-stressed plants, and 19 were identified under only flooding stress conditions. The main functional categories were protein and development-related proteins. Protein-protein interaction analysis revealed that zincin-like metalloprotease and cupin family proteins were found to highly interact with other proteins under flooding stress. Plant stearoyl acyl-carrier protein, ascorbate peroxidase 1, and secretion-associated RAS superfamily 2 were down-regulated, whereas ferretin 1 was up-regulated at the transcription level. Notably, the levels of all corresponding proteins were decreased, indicating that mRNA translation to proteins is impaired under flooding conditions. Decreased levels of ferritin may lead to a strong deregulation of the expression of several metal transporter genes and over-accumulation of iron, which led to increased levels of reactive oxygen species, resulting to detoxification of these reactive species. Taken together, these results suggest that ferritin might have an essential role in protecting plant cells against oxidative damage under flooding conditions.

BIOLOGICAL SIGNIFICANCE

This study reported the comparative proteomic analysis of cotyledon of soybean plants between non-flooding and flooding conditions using the gel-free quantitative techniques. Mass spectrometry analysis of the proteins from cotyledon resulted in the identification of a total of 165 proteins under flooding stress. These proteins were assigned to different functional categories, such as protein, development, stress, redox, and glycolysis. Therefore, this study provides not only the comparative proteomic analysis but also the molecular mechanism underlying the flooding responsive protein functions in the cotyledon.

Localization of tobacco germin-like protein 1 in leaf intercellular space

To characterize leaf cell wall proteins relating the architectural changes of leaves, we analyzed Nicotiana tabacum leaf cell wall proteins that were extracted by the treatment with lithium chloride. Some of these proteins showed amino acid sequence homology to some germin-like proteins (GLP). Based of those sequences, we isolated the cDNA encoding the GLPs (NtGLP1-1, NtGLP2-1). Phylogenetic analysis including de novo assembled tobacco GLPs using EST clones, revealed that tobacco GLPs belong to at least 5 different subgroups of GLP and both NtGLP1 and NtGLP2 belong to GLP subfamily 3. We showed that the NtGLP1 actually localizes to cell wall and revealed that it predominantly localized at specific sites on the leaf cell wall where intercellular attachment was just bifurcated. Expression of the NtGLP1 mRNA was mainly detected in leaves especially at elongating stage. NtGLP1 is possibly relevant to development of leaf intercellular space.

Peanut allergens: an overview

Peanut is recognized as a potent food allergen producing one of the most frequent food allergies. This fact has originated the publication of an elevated number of scientific reports dealing with peanut allergens and, especially, the prevalence of peanut allergy. For this reason, the information available on peanut allergens is increasing and the debate about peanut allergy is always renewed. This article reviews the information currently available on peanut allergens and on the techniques used for their chemical characterization. Moreover, a general overview on the current biotechnological approaches used to reduce or eliminate peanut allergens is also provided.