The potential of Betv1 homologues, a nuclear multigene family, as phylogenetic markers in flowering plants

Ecological factors influence balancing selection on leaf chemical profiles of a wildflower

Balancing selection is frequently invoked as a mechanism that maintains variation within and across populations. However, there are few examples of balancing selection operating on loci underpinning complex traits, which frequently display high levels of variation. We investigated mechanisms that may maintain variation in a focal polymorphism-leaf chemical profiles of a perennial wildflower (Boechera stricta, Brassicaceae)-explicitly interrogating multiple ecological and genetic processes including spatial variation in selection, antagonistic pleiotropy and frequency-dependent selection. A suite of common garden and greenhouse experiments showed that the alleles underlying variation in chemical profile have contrasting fitness effects across environments, implicating two ecological drivers of selection on chemical profile: herbivory and drought. Phenotype-environment associations and molecular genetic analyses revealed additional evidence of past selection by these drivers. Together, these data are consistent with balancing selection on chemical profile, probably caused by pleiotropic effects of secondary chemical biosynthesis genes on herbivore defence and drought response.

Review: Biological functions of major latex-like proteins in plants

Major latex-like proteins (MLPs) have been identified in dicots and monocots. They are members of the birch pollen allergen Bet v 1 family as well as pathogenesis-related proteins class 10. MLPs have two main features. One is binding affinity toward various hydrophobic compounds, such as long-chain fatty acids, steroids, and systemic acquired resistance signals, via its internal hydrophobic cavity or hydrophobic residues on its surface. MLPs transport such compounds to other organs via phloem and xylem vessels and contribute to the expression of physiologically important ligands' activity in the particular organs. The second feature is responses to abiotic and biotic stresses. MLPs are involved in drought and salt tolerance through the mediation of plant hormone signaling pathways. MLPs generate resistance against pathogens by the induction of pathogenesis-related protein genes. Therefore, MLPs play crucial roles in drought and salt tolerance and resistance against pathogens. However, knowledge of MLPs is fragmented, and an overview of them is needed. Herein, we summarize the current knowledge of the biological functions of MLPs, which to our knowledge, is the first review about MLPs that has been reported.

Phosphorylation-dependent ribonuclease activity of Fra a 1 proteins

Abiotic and biotic stress situations cause the upregulation of the transcription of a number of plant defence genes. They code for so-called pathogenesis-related (PR) proteins such as PR proteins of class-10 (PR-10), whose biological functions are still unclear. PR10 proteins are members of the Bet v 1 (major birch pollen allergen) superfamily including related proteins from the cultivated strawberry Fragaria × ananassa (Fra a 1 proteins). Here, we analyzed the expression of 21 Fra a 1 genes in different tissues of the strawberry plant by quantitative real-time PCR. Thirteen members were mainly expressed in roots, three in stems, two in red fruits and leaves, and one in flowers. Five genes (Fra a 1.04-1.08) were selected based on their expression profiles, heterologously expressed in Escherichia coli, and their recombinant proteins functionally characterized. Ribonuclease activity, demonstrated by in-solution and in-gel RNA degradation assays, indicated complete hydrolysis of RNA only by Fra a 1.06. Moreover, phosphorylation assays showed that except for Fra a 1.06, the remaining four recombinant proteins were phosphorylated. Consequently, we investigated whether the phosphorylation status of the proteins affects their ribonuclease activity. Using an in-solution as well as an in-gel RNase activity assay, results demonstrated that the four recombinant proteins, dephosphorylated with phosphatases, exhibited ribonucleolytic activity against total RNA. Thus, the PR10 related proteins characterized in this study harbour a phosphorylation-dependent RNase activity. The results shed new light on the assumed function of PR10 proteins in plant defence.

Cloning and characterization of norbelladine synthase catalyzing the first committed reaction in Amaryllidaceae alkaloid biosynthesis

BACKGROUND

Amaryllidaceae alkaloids (AAs) are a large group of plant-specialized metabolites displaying an array of biological and pharmacological properties. Previous investigations on AA biosynthesis have revealed that all AAs share a common precursor, norbelladine, presumably synthesized by an enzyme catalyzing a Mannich reaction involving the condensation of tyramine and 3,4-dihydroxybenzaldehyde. Similar reactions have been reported. Specifically, norcoclaurine synthase (NCS) which catalyzes the condensation of dopamine and 4-hydroxyphenylacetaldehyde as the first step in benzylisoquinoline alkaloid biosynthesis.

RESULTS

With the availability of wild daffodil (Narcissus pseudonarcissus) database, a transcriptome-mining search was performed for NCS orthologs. A candidate gene sequence was identified and named norbelladine synthase (NBS). NpNBS encodes for a small protein of 19 kDa with an anticipated pI of 5.5. Phylogenetic analysis showed that NpNBS belongs to a unique clade of PR10/Bet v1 proteins and shared 41% amino acid identity to opium poppy NCS1. Expression of NpNBS cDNA in Escherichia coli produced a recombinant enzyme able to condense tyramine and 3,4-DHBA into norbelladine as determined by high-resolution tandem mass spectrometry.

CONCLUSIONS

Here, we describe a novel enzyme catalyzing the first committed step of AA biosynthesis, which will facilitate the establishment of metabolic engineering and synthetic biology platforms for the production of AAs.

Improved Shoot Regeneration, Salinity Tolerance and Reduced Fungal Susceptibility in Transgenic Tobacco Constitutively Expressing PR-10a Gene

Plants in ecosystems are simultaneously exposed to abiotic and biotic stresses, which restrict plant growth and development. The complex responses to these stresses are largely regulated by plant hormones, which in turn, orchestrate the different biochemical and molecular pathways to maneuver stress tolerance. The PR-10 protein family is reported to be involved in defense regulation, stress response and plant growth and development. The JcPR-10a overexpression resulted in increased number of shoot buds in tobacco (Nicotiana tabacum), which could be due to high cytokinin to auxin ratio in the transgenics. The docking analysis shows the binding of three BAP molecules at the active sites of JcPR-10a protein. JcPR-10a transgenics showed enhanced salt tolerance, as was evident by increased germination rate, shoot and root length, relative water content, proline, soluble sugar and amino acid content under salinity. Interestingly, the transgenics also showed enhanced endogenous cytokinin level as compared to WT, which, further increased with salinity. Exposure of gradual salinity resulted in increased stomatal conductance, water use efficiency, photosynthesis rate and reduced transpiration rate. Furthermore, the transgenics also showed enhanced resistance against Macrophomina fungus. Thus, JcPR-10a might be working in co-ordination with cytokinin signaling in mitigating the stress induced damage by regulating different stress signaling pathways, leading to enhanced stress tolerance.

A pathogenesis related-10 protein CaARP functions as aldo/keto reductase to scavenge cytotoxic aldehydes

Pathogenesis related-10 (PR-10) proteins are present as multigene family in most of the higher plants. The role of PR-10 proteins in plant is poorly understood. A sequence analysis revealed that a large number of PR-10 proteins possess conserved motifs found in aldo/keto reductases (AKRs) of yeast and fungi. We took three PR-10 proteins, CaARP from chickpea, ABR17 from pea and the major pollen allergen Bet v1 from silver birch as examples and showed that these purified recombinant proteins possessed AKR activity using various cytotoxic aldehydes including methylglyoxal and malondialdehyde as substrates and the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) as co-factor. Essential amino acids for this catalytic activity were identified by substitution with other amino acids. CaARP was able to discriminate between the reduced and oxidized forms of NADP independently of its catalytic activity and underwent structural change upon binding with NADPH. CaARP protein was preferentially localized in cytosol. When expressed in bacteria, yeast or plant, catalytically active variants of CaARP conferred tolerance to salinity, oxidative stress or cytotoxic aldehydes. CaARP-expressing plants showed lower lipid peroxidation product content in presence or absence of stress suggesting that the protein functions as a scavenger of cytotoxic aldehydes produced by metabolism and lipid peroxidation. Our result proposes a new biochemical property of a PR-10 protein.

A Novel Pathogenesis-Related Class 10 Protein Gly m 4l, Increases Resistance upon Phytophthora sojae Infection in Soybean (Glycine max [L.] Merr.)

Phytophthora root and stem rot of soybean, caused by Phytophthora sojae (P. sojae), is a destructive disease in many soybean planting regions worldwide. In a previous study, an expressed sequence tag (EST) homolog of the major allergen Pru ar 1 in apricot (Prunus armeniaca) was identified up-regulated in the highly resistant soybean 'Suinong 10' infected with P. sojae. Here, the full length of the EST was isolated using rapid amplification of cDNA ends (RACE). It showed the highest homology of 53.46% with Gly m 4 after comparison with the eight soybean allergen families reported and was named Gly m 4-like (Gly m 4l, GenBank accession no. HQ913577.1). The cDNA full length of Gly m 4l was 707 bp containing a 474 bp open reading frame encoding a polypeptide of 157 amino acids. Sequence analysis suggests that Gly m 4l contains a conserved 'P-loop' (phosphate-binding loop) motif at residues 47-55 aa and a Bet v 1 domain at residues 87-120 aa. The transcript abundance of Gly m 4l was significantly induced by P. sojae, salicylic acid (SA), NaCl, and also responded to methyl jasmonic acid (MeJA) and ethylene (ET). The recombinant Gly m 4l protein showed RNase activity and displayed directly antimicrobial activity that inhibited hyphal growth and reduced zoospore release in P. sojae. Further analyses showed that the RNase activity of the recombinant protein to degrading tRNA was significantly affected in the presence of zeatin. Over-expression of Gly m 4l in susceptible 'Dongnong 50' soybean showed enhanced resistance to P. sojae. These results indicated that Gly m 4l protein played an important role in the defense of soybean against P. sojae infection.

Tree pollen allergens-an update from a molecular perspective

It is estimated that pollen allergies affect approximately 40% of allergic individuals. In general, tree pollen allergies are mainly elicited by allergenic trees belonging to the orders Fagales, Lamiales, Proteales, and Pinales. Over 25 years ago, the gene encoding the major birch pollen allergen Bet v 1 was the first such gene to be cloned and its product characterized. Since that time, 53 tree pollen allergens have been identified and acknowledged by the WHO/IUIS allergen nomenclature subcommittee. Molecule‐based profiling of allergic sensitization has helped to elucidate the immunological connections of allergen cross‐reactivity, whereas advances in biochemistry have revealed structural and functional aspects of allergenic proteins. In this review, we provide a comprehensive overview of the present knowledge of the molecular aspects of tree pollen allergens. We analyze the geographic distribution of allergenic trees, discuss factors pivotal for allergic sensitization, and describe the role of tree pollen panallergens. Novel allergenic tree species as well as tree pollen allergens are continually being identified, making research in this field highly competitive and instrumental for clinical applications.

Development of a Sandwich ELISA for Quantification of Gly m 4, a Soybean Allergen

Gly m 4 is a key soybean allergen that causes allergic symptoms in the skin, gastrointestinal tract, or respiratory tract of sensitive individuals. To understand naturally variable levels of Gly m 4 among conventional soybean varieties, a sandwich ELISA was developed and validated using a mouse anti-Gly m 4 monoclonal antibody and a goat anti-Gly m 4 polyclonal antibody as capture and detection antibodies, respectively. The ELISA shows high specificity to Gly m 4 without any cross-reactivity to other soybean proteins and has a quantification range of 7.8-250 ng/mL using an Escherichia coli-produced recombinant Gly m 4, with 2.1 ng/mL being the limit of detection. Within the quantification range, the coefficients of variation of the intra-assay and interassay precision are less than 5 and 12%, respectively. Moreover, extraction efficiency and dilutional parallelism experiments were completed to demonstrate the assay is accurate. The validated assay was used to quantify Gly m 4 levels in 128 soybean samples from 24 conventional soybean varieties grown at 8 distinct geographical locations. There was a 13-fold difference between the least and greatest amounts of Gly m 4 concentrations among the samples, and the results demonstrate that the most significant sources of variability in Gly m 4 levels in the conventional varieties were related to location and variety.

Specific binding of gibberellic acid by cytokinin-specific binding proteins: a new aspect of plant hormone-binding proteins with the PR-10 fold

Pathogenesis-related proteins of class 10 (PR-10) are a family of plant proteins with the same fold characterized by a large hydrophobic cavity that allows them to bind various ligands, such as phytohormones. A subfamily with only ~20% sequence identity but with a conserved canonical PR-10 fold have previously been recognized as Cytokinin-Specific Binding Proteins (CSBPs), although structurally the binding mode of trans-zeatin (a cytokinin phytohormone) was found to be quite diversified. Here, it is shown that two CSBP orthologues from Medicago truncatula and Vigna radiata bind gibberellic acid (GA3), which is an entirely different phytohormone, in a conserved and highly specific manner. In both cases a single GA3 molecule is found in the internal cavity of the protein. The structural data derived from high-resolution crystal structures are corroborated by isothermal titration calorimetry (ITC), which reveals a much stronger interaction with GA3 than with trans-zeatin and pH dependence of the binding profile. As a conclusion, it is postulated that the CSBP subfamily of plant PR-10 proteins should be more properly linked with general phytohormone-binding properties and termed phytohormone-binding proteins (PhBP).

Pathogenesis related-10 proteins are small, structurally similar but with diverse role in stress signaling

Pathogenesis related-10 proteins are small proteins with cytosolic localization, conserved three dimensional structures and single intron at 185 bp position. These proteins have a broad spectrum of roles significantly in biotic and abiotic stresses. The RNase activity, ligand binding activity, posttranslational modification (phosphorylation) and phytohormone signaling provide some information into the mechanism of the regulation of PR-10 proteins, however the presence of isoforms makes it difficult to decipher its exact mode of function. The involvement of phosphorylation/dephosphorylation events in its activation is interesting and provides unique and unbiased insights into the complexity of its regulation. Studies on upstream region of different PR-10 genes indicate the presence of cis-acting elements for WRKY, RAVI, bZ1P, ERF, SEBF and Pti4 transcription factors indicating their role in regulating PR-10 promoter. In this review, we discuss in detail the structure and mechanism of regulation of PR-10 proteins.

Food proteins from different allergen families sensitize Balb/c mice to family-specific immune responses

The classification of food allergens based on the structure and function of proteins contributes to the study of the relationship between bioinformatics and potential allergenicity of allergens. Food allergens always share sequence similarity with the allergens in the same allergen families. For that reason, food proteins from different allergen families may induce different patterns of immune responses in animal models. Female Balb/c mice (3-4-weeks-old) were sensitized with food proteins once per week for 4 weeks, and then challenged 2 weeks later (on Day 42 of study). Blood was collected (to obtain serum levels of histamine and protein-specific IgG1 and IgE antibodies) and measures of vascular permeability were performed 20 min after the challenge. Five food proteins (11S globulin, OVA [ovalbumin], HAS [human serum albumin] and LRP [lysine-responsive storage protein] of different allergen families, and Cry 1Ab/Ac [crystal protein]) were used to assess patterns of immune responses for each allergen family and then bioinformatics and digestive stability in simulated gastric fluid were employed to assess the overall utility of the Balb/c. The assay results indicated that, in this model, histamine and protein-specific IgE antibody levels and vascular permeability could be used to identify allergenicity of 11S globulin, OVA, and PAP (potato acid phosphatase) only. However, the results of the protein-specific IgG1 measures could only distinguish allergic food proteins with negative control. Based on bioinformatic analyses, the five different food proteins clearly induced distinct patterns of immune responses in the Balb/c model.

Structural and functional aspects of PR-10 proteins

Physical, chemical and biological stress factors, such as microbial infection, upregulate the transcription levels of a number of plant genes, coding for the so-called pathogenesis-related (PR) proteins. For PR proteins of class-10 (PR-10), the biological function remains unclear, despite two decades of scientific research. PR-10 proteins have a wide distribution throughout the plant kingdom and the class members share size and secondary structure organization. Throughout the years, we and other groups have determined the structures of a number of PR-10 proteins, both in the crystalline state by X-ray diffraction and in solution by NMR spectroscopy. Despite the accumulating structural information, our understanding of PR-10 function is still limited. PR-10 proteins are rather small (~ 160 amino acids) with a fold consisting of three α helices and seven antiparallel β strands. These structural elements enclose a large hydrophobic cavity that is most probably the key to their functional relevance. Also, the outer surface of these proteins is of extreme interest, as epitopes from a PR-10 subclass cause allergic reactions in humans.

Changes in expression of BetV1 allergen of silver birch pollen in urbanized area of Ukraine

The aim of the study was to determinate the level of expression of silver birch allergen Betv1 in pollen samples from different Ukraine areas by RT-qPCR SYBR Green assay. Protocol for quantifying the expression of Betv1 allergen was developed when testing of three housekeeping genes-cyclophylin, alpha-tubulin and transcription factor CBF1. Samples from urbanized area was analysed by real-time PCR when a sample from forest growth conditions was used as a calibrator. Real-time PCR based quantifying of Betv1 provides a useful method for rapid and sensitive analyses of this silver birch allergen. Our results show higher expression levels in samples from central parts of urbanized area as housing estates when compared to the samples from borders of the urbanized area.

Putting the pieces together: high-performance LC-MS/MS provides network-, pathway-, and protein-level perspectives in Populus

High-performance mass spectrometry (MS)-based proteomics enabled the construction of a detailed proteome atlas for Populus, a woody perennial plant model organism. Optimization of experimental procedures and implementation of current state-of-the-art instrumentation afforded the most detailed look into the predicted proteome space of Populus, offering varying proteome perspectives: (1) network-wide, (2) pathway-specific, and (3) protein-level viewpoints. Together, enhanced protein retrieval through a detergent-based lysis approach and maximized peptide sampling via the dual-pressure linear ion trap mass spectrometer (LTQ Velos), have resulted in the identification of 63,056 tryptic peptides. The technological advancements, specifically spectral-acquisition and sequencing speed, afforded the deepest look into the Populus proteome, with peptide abundances spanning 6 orders of magnitude and mapping to ∼25% of the predicted proteome space. In total, tryptic peptides mapped to 11,689 protein assignments across four organ-types: mature (fully expanded, leaf plastichronic index (LPI) 10-12) leaf, young (juvenile, LPI 4-6) leaf, root, and stem. To resolve protein ambiguity, identified proteins were grouped by sequence similarity (≥ 90%), thereby reducing the protein assignments into 7538 protein groups. In addition, this large-scale data set features the first systems-wide survey of protein expression across different Populus organs. As a demonstration of the precision and comprehensiveness of the semiquantitative analysis, we were able to contrast two stages of leaf development, mature versus young leaf. Statistical comparison through ANOVA analysis revealed 1432 protein groups that exhibited statistically significant (p ≤ 0.01) differences in protein abundance. Experimental validation of the metabolic circuitry expected in mature leaf (characterized by photosynthesis and carbon fixation) compared with young leaf (characterized by rapid growth and moderate photosynthetic activities) strongly testifies to the credibility of the approach. Instead of quantitatively comparing a few proteins, a systems view of all the changes associated with a given cellular perturbation could be made.

Characterisation of the Vitis vinifera PR10 multigene family

BACKGROUND

Genes belonging to the pathogenesis related 10 (PR10) group have been studied in several plant species, where they form multigene families. Until now, such an analysis has not been performed in Vitis vinifera, although three different PR10 genes were found to be expressed under pathogen attack or abiotic stress, and during somatic embryogenesis induction. We used the complete genome sequence for characterising the whole V. vinifera PR10 gene family. The expression of candidate genes was studied in various non-treated tissues and following somatic embryogenesis induction by the auxin 2,4-D.

RESULTS

In addition to the three V. vinifera PR10 genes already described, namely VvPR10.1, VvPR10.2 and VvPR10.3, fourteen different PR10 related sequences were identified. Showing high similarity, they form a single cluster on the chromosome 5 comprising three pseudogenes. The expression of nine different genes was detected in various tissues. Although differentially expressed in non-treated plant organs, several genes were up-regulated in tissues treated with 2,4-D, as expected for PR genes.

CONCLUSIONS

PR10 genes form a multigene family in V. vinifera, as found in birch, apple or peach. Seventeen closely related PR10 sequences are arranged in a tandem array on the chromosome 5, probably reflecting small-scale duplications during evolution. Various expression patterns were found for nine studied genes, highlighting functional diversification. A phylogenetic comparison of deduced proteins with PR10 proteins of other plants showed a characteristic low intraspecific variability. Particularly, a group of seven close tandem duplicates including VvPR10.1, VvPR10.2 and VvPR10.3 showed a very high similarity, suggesting concerted evolution or/and recent duplications.

The strawberry fruit Fra a allergen functions in flavonoid biosynthesis

The strawberry Fra a 1 allergen is a homolog of the major birch pollen allergen Bet v 1. It is synthesized by red ripe fruits of Fragaria x ananassa while white fruits of a mutant genotype, which is known to be tolerated by individuals affected by allergy, are devoid of it. Proteomic analyses have shown that Fra a 1 is down-regulated in the tolerated white-fruited genotype along with enzymes of the anthocyanin pigment pathway. In this study, we report the spatial and temporal expression of three Fra a genes that encode different isoforms, and the transient RNAi-mediated silencing of the Fra a genes in strawberry fruits of the red-fruited cultivar Elsanta with an ihpRNA construct. As a consequence of reduced levels of Fra a mRNAs, fruits were obtained that produced significantly decreased levels of anthocyanins and upstream metabolites. This effect is consistent with the parallel down-regulation of the phenylalanine ammonia lyase (FaPAL) and to a lesser extent of the chalcone synthase (FaCHS) transcript levels also found in these fruits. In naturally occurring white-fruited genotypes of F. chiloensis and F. vesca, Fra a transcript levels are higher than those of the red-fruited varieties, likely to compensate for the low expression levels of FaPAL and FaCHS in these mutant genotypes. The results demonstrate that Fra a expression is directly linked to flavonoid biosynthesis and show that the Fra a allergen has an essential biological function in pigment formation in strawberry fruit.

Bioinformatics and structural characterization of a hypothetical protein from Streptococcus mutans: implication of antibiotic resistance

As an oral bacterial pathogen, Streptococcus mutans has been known as the aetiologic agent of human dental caries. Among a total of 1960 identified proteins within the genome of this organism, there are about 500 without any known functions. One of these proteins, SMU.440, has very few homologs in the current protein databases and it does not fall into any protein functional families. Phylogenetic studies showed that SMU.440 is related to a particular ecological niche and conserved specifically in some oral pathogens, due to lateral gene transfer. The co-occurrence of a MarR protein within the same operon among these oral pathogens suggests that SMU.440 may be associated with antibiotic resistance. The structure determination of SMU.440 revealed that it shares the same fold and a similar pocket as polyketide cyclases, which indicated that it is very likely to bind some polyketide-like molecules. From the interlinking structural and bioinformatics studies, we have concluded that SMU.440 could be involved in polyketide-like antibiotic resistance, providing a better understanding of this hypothetical protein. Besides, the combination of multiple methods in this study can be used as a general approach for functional studies of a protein with unknown function.

Differential regulation of SERK, LEC1-like and pathogenesis-related genes during indirect secondary somatic embryogenesis in grapevine

A culture model was developed in Vitis vinifera L., cultivar 'Chardonnay' for studying SE (Somatic Embryogenesis). The auxin 2,4-D (2,4-Dichlorophenoxyacetic acid) was used to induce indirect secondary embryogenesis at a high rate, starting from embryos derived from embryogenic cultures previously obtained. Cotyledonary embryos were shown to be more responsive to SE induction than embryos at the torpedo-stage and were used for molecular analyses. The expression of SERK (Somatic Embryogenesis Receptor Kinase), L1L (Leafy Cotyledon1 Like) and a set of PR (Pathogenesis-Related) genes was monitored during the whole SE process. VvSERK1, VvSERK2 and VvL1L were down-regulated by the 2,4-D treatment but expressed in embryonic tissues. On the contrary, VvPR1, VvPR8, VvPR10.1 and VvPR10.3 were strongly up-regulated by the 2,4-D treatment, and their transcripts were not or only weakly detected in clusters of secondary embryos. VvSERK3, VvPR3 and VvPR10.2 were more stably expressed in all tissues examined. The discussion deals with the putative role of the different genes in grapevine SE.

Characterization of PR-10 genes from eight Betula species and detection of Bet v 1 isoforms in birch pollen

BACKGROUND

Bet v 1 is an important cause of hay fever in northern Europe. Bet v 1 isoforms from the European white birch (Betula pendula) have been investigated extensively, but the allergenic potency of other birch species is unknown. The presence of Bet v 1 and closely related PR-10 genes in the genome was established by amplification and sequencing of alleles from eight birch species that represent the four subgenera within the genus Betula. Q-TOF LC-MSE was applied to identify which PR-10/Bet v 1 genes are actually expressed in pollen and to determine the relative abundances of individual isoforms in the pollen proteome.

RESULTS

All examined birch species contained several PR-10 genes. In total, 134 unique sequences were recovered. Sequences were attributed to different genes or pseudogenes that were, in turn, ordered into seven subfamilies. Five subfamilies were common to all birch species. Genes of two subfamilies were expressed in pollen, while each birch species expressed a mixture of isoforms with at least four different isoforms. Isoforms that were similar to isoforms with a high IgE-reactivity (Bet v 1a = PR-10.01A01) were abundant in all species except B. lenta, while the hypoallergenic isoform Bet v 1d (= PR-10.01B01) was only found in B. pendula and its closest relatives.

CONCLUSION

Q-TOF LC-MSE allows efficient screening of Bet v 1 isoforms by determining the presence and relative abundance of these isoforms in pollen. B. pendula contains a Bet v 1-mixture in which isoforms with a high and low IgE-reactivity are both abundant. With the possible exception of B. lenta, isoforms identical or very similar to those with a high IgE-reactivity were found in the pollen proteome of all examined birch species. Consequently, these species are also predicted to be allergenic with regard to Bet v 1 related allergies.

The Bet v 1 fold: an ancient, versatile scaffold for binding of large, hydrophobic ligands

Background

The major birch pollen allergen, Bet v 1, is a member of the ubiquitous PR-10 family of plant pathogenesis-related proteins. In recent years, a number of diverse plant proteins with low sequence similarity to Bet v 1 was identified. In addition, determination of the Bet v 1 structure revealed the existence of a large superfamily of structurally related proteins. In this study, we aimed to identify and classify all Bet v 1-related structures from the Protein Data Bank and all Bet v 1-related sequences from the Uniprot database.

Results

Structural comparisons of representative members of already known protein families structurally related to Bet v 1 with all entries of the Protein Data Bank yielded 47 structures with non-identical sequences. They were classified into eleven families, five of which were newly identified and not included in the Structural Classification of Proteins database release 1.71. The taxonomic distribution of these families extracted from the Pfam protein family database showed that members of the polyketide cyclase family and the activator of Hsp90 ATPase homologue 1 family were distributed among all three superkingdoms, while members of some bacterial families were confined to a small number of species. Comparison of ligand binding activities of Bet v 1-like superfamily members revealed that their functions were related to binding and metabolism of large, hydrophobic compounds such as lipids, hormones, and antibiotics. Phylogenetic relationships within the Bet v 1 family, defined as the group of proteins with significant sequence similarity to Bet v 1, were determined by aligning 264 Bet v 1-related sequences. A distance-based phylogenetic tree yielded a classification into 11 subfamilies, nine exclusively containing plant sequences and two subfamilies of bacterial proteins. Plant sequences included the pathogenesis-related proteins 10, the major latex proteins/ripening-related proteins subfamily, and polyketide cyclase-like sequences.

Conclusion

The ubiquitous distribution of Bet v 1-related proteins among all superkingdoms suggests that a Bet v 1-like protein was already present in the last universal common ancestor. During evolution, this protein diversified into numerous families with low sequence similarity but with a common fold that succeeded as a versatile scaffold for binding of bulky ligands.

Evolutionary biology of plant food allergens

The majority of plant food allergens can be grouped into just 4 protein families. This review summarizes the evolutionary relationships of allergenic and nonallergenic members of these families. Proteins from the prolamin superfamily have been described in vascular plants. This superfamily contains several allergenic (2S albumins, nonspecific lipid transfer proteins, and cereal amylase and protease inhibitors) and nonallergenic (hybrid proline-rich proteins, cereal indolines, and alpha-globulins) member families. The cupin superfamily comprises numerous functionally highly diverse protein families from all groups of organisms. However, allergenicity within the cupins is confined to the vicilin and legumin seed storage proteins. Profilins are ubiquitous eukaryotic proteins that are nonallergenic, with the exception of profilins from flowering plants. Finally, the Bet v 1 superfamily contains the pathogenesis-related proteins 10 family, the family of major latex proteins and ripening-related proteins, the norcoclaurine synthases, and the cytokinin-binding proteins, with pathogenesis-related proteins 10 family members from certain taxa being the only allergenic members. The study of the distribution of allergenic and nonallergenic members of protein families will provide new insights into the evolution of allergenicity and the factors that make proteins allergenic.

Silencing of PR-10-like proteins in Medicago truncatula results in an antagonistic induction of other PR proteins and in an increased tolerance upon infection with the oomycete Aphanomyces euteiches

Recent studies on the root proteome of Medicago truncatula (Gaertn.) showed an induction of pathogenesis-related (PR) proteins of the class 10 after infection with the oomycete pathogen Aphanomyces euteiches (Drechs.). To get insights into the function of these proteins during the parasitic root-microbe association, a gene knockdown approach using RNAi was carried out. Agrobacterium rhizogenes-mediated transformation of M. truncatula roots led to a knockdown of the Medicago PR10-1 gene in transgenic in vitro root cultures. Proteomic analyses of the MtPr10-1i root cultures showed that MtPr10-1 was efficiently knocked down in two MtPr10-1i lines. Moreover, five additional PR-10-type proteins annotated as abscisic acid responsive proteins (ABR17s) revealed also an almost complete silencing in these two lines. Inoculation of the root cultures with the oomycete root pathogen A. euteiches resulted in a clearly reduced colonization and thus in a suppressed infection development in MtPr10-1i roots as compared to that in roots of the transformation controls. In addition, MtPr10-1 silencing led to the induction of a new set of PR proteins after infection with A. euteiches including the de novo induction of two isoforms of thaumatin-like proteins (PR-5b), which were not detectable in A. euteiches-infected control roots. Thus, antagonistic induction of other PR proteins, which are normally repressed due to PR-10 expression, is supposed to cause an increased resistance of M. truncatula upon an A. euteiches in vitro infection. The results were also further confirmed by detecting increased PR-5b induction levels in 2-D gels of a previously analyzed M. truncatula line (F83.005-9) exhibiting increased A. euteiches tolerance associated with reduced PR-10 induction levels.

Seven different genes encode a diverse mixture of isoforms of Bet v 1, the major birch pollen allergen

Background

Pollen of the European white birch (Betula pendula, syn. B. verrucosa) is an important cause of hay fever. The main allergen is Bet v 1, member of the pathogenesis-related class 10 (PR-10) multigene family. To establish the number of PR-10/Bet v 1 genes and the isoform diversity within a single tree, PCR amplification, cloning and sequencing of PR-10 genes was performed on two diploid B. pendula cultivars and one interspecific tetraploid Betula hybrid. Sequences were attributed to putative genes based on sequence identity and intron length. Information on transcription was derived by comparison with homologous cDNA sequences available in GenBank/EMBL/DDJB. PCR-cloning of multigene families is accompanied by a high risk for the occurrence of PCR recombination artifacts. We screened for and excluded these artifacts, and also detected putative artifact sequences among database sequences.

Results

Forty-four different PR-10 sequences were recovered from B. pendula and assigned to thirteen putative genes. Sequence homology suggests that three genes were transcribed in somatic tissue and seven genes in pollen. The transcription of three other genes remains unknown. In total, fourteen different Bet v 1-type isoforms were identified in the three cultivars, of which nine isoforms were entirely new. Isoforms with high and low IgE-reactivity are encoded by different genes and one birch pollen grain has the genetic background to produce a mixture of isoforms with varying IgE-reactivity. Allergen diversity is even higher in the interspecific tetraploid hybrid, consistent with the presence of two genomes.

Conclusion

Isoforms of the major birch allergen Bet v 1 are encoded by multiple genes, and we propose to name them accordingly. The present characterization of the Bet v 1 genes provides a framework for the screening of specific Bet v 1 genes among other B. pendula cultivars or Betula species, and for future breeding for trees with a reduced allergenicity. Investigations towards sensitization and immunotherapy should anticipate that patients are exposed to a mixture of Bet v 1 isoforms of different IgE-reactivity, even if pollen originates from a single birch tree.

Proteomic analysis of grapevine (Vitis vinifera L.) tissues subjected to herbicide stress

Two-dimensional gel electrophoresis coupled to mass spectrometry analysis was used to examine for the first time the effect of a herbicide (flumioxazin) on a crop species (Vitis vinifera L.) at the proteome level. Examination of 2-D maps derived from chemically stressed tissues revealed the presence of 33 spots displaying a differential expression pattern. The presence of stress responsive proteins in the different plant organs analysed suggests that flumioxazin could act systemically. Among the responsive proteins, some photosynthesis-related proteins, including several fragments of the enzyme Rubisco, were identified. This effect suggests that photosynthesis could be impaired by the herbicide. The induction of several enzymatic antioxidant systems was also observed, probably as a result of an oxidative stress. Moreover, the photorespiration pathway was stimulated, as suggested by the induction of some key enzymes involved in this process. Changes in carbon metabolism-associated proteins presumably reflect altered patterns of carbon flux in response to impaired photosynthesis and an increased need for osmotic adjustment in affected tissues. Finally, plant defences were stimulated as revealed by the induction of a set of proteins belonging to the pathogenesis-related 10 class, suggesting that they could play an essential role in cell defence mechanisms against flumioxazin.

Molecular investigations of pathogenesis-related Bet v 1 homologues in Passiflora (Passifloraceae)

The major birch pollen allergen, Bet v 1, responsible for allergic reactions in many areas of the world, is homologous to a large number of pathogenesis-related proteins (PRs), identified as PR10. As part of a long-range investigation of these types of proteins and of evolution in Passiflora, DNA sequences from eight Bet v 1 homologue isoforms were obtained from five species of this genus in Brazil, and their sequences compared among themselves and with 30 others from 8 different species, classified in different taxonomic units. The objective was a first characterization of these PRs in wild passionflowers, and their use for evolutionary and applied investigations. High interspecific, but low intraspecific variability was observed, as expected from multigenic families subjected to concerted evolution. The relationships obtained both within Passiflora and between it and seven other genera probably best reflect functional similarities than evolutionary history.

Genomic cloning and linkage mapping of the Mal d 1 (PR-10) gene family in apple (Malus domestica)

Fresh apples can cause birch pollen-related food allergy in northern and central European populations, primarily because of the presence of Mal d 1, the major apple allergen that is cross-reactive to the homologous and sensitizing allergen Bet v 1 from birch. Apple cultivars differ significantly in their allergenicity. Knowledge of the genetic basis of these differences would direct breeding for hypoallergenic cultivars. The PCR genomic cloning and sequencing were performed on two cultivars, Prima and Fiesta, which resulted in 37 different Mal d 1 gDNA sequences. Based on the mapping of sequence-specific molecular markers, these sequences appeared to represent 18 Mal d 1 genes. Sixteen genes were located in two clusters, one cluster with seven genes on linkage group (LG) 13, and the other cluster with nine genes on the homoeologous LG 16. One gene was mapped on LG 6, and one remained unmapped. According to sequence identity, these 18 genes could be subdivided into four subfamilies. Subfamilies I-III had an intron of different size that was subfamily and gene-specific. Subfamily IV consisted of 11 intronless genes. The deduced amino acid sequence identity varied from 65% to 81% among subfamilies, from 82% to 100% among genes within a subfamily, and from 97.5% to 100% among alleles of one gene. This study provides a better understanding of the genetics of Mal d 1 and the basis for further research on the occurrence of allelic diversity among cultivars in relation to allergenicity and their biological functions.

Evolution of a RNA Polymerase Gene Family in Silene (Caryophyllaceae)—Incomplete Concerted Evolution and Topological Congruence Among Paralogues

Four low-copy nuclear DNA intron regions from the second largest subunits of the RNA polymerase gene family (RPA2, RPB2, RPD2a, and RPD2b), the internal transcribed spacers (ITSs) from the nuclear ribosomal regions, and the rps16 intron from the chloroplast were sequenced and used in a phylogenetic analysis of 29 species from the tribe Sileneae (Caryophyllaceae). We used a low stringency nested polymerase chain reaction (PCR) approach to overcome the difficulties of constructing specific primers for amplification of the low copy nuclear DNA regions. Maximum parsimony analyses resulted in largely congruent phylogenetic trees for all regions. We tested overall model congruence in a likelihood context using the software PLATO and found that ITSs, RPA2, and RPB2 deviated from the maximum likelihood model for the combined data. The topology parameter was then isolated and topological congruence assessed by nonparametric bootstrapping. No strong topological incongruence was found. The analysis of the combined data sets resolves previously poorly known major relationships within Sileneae. Two paralogues of RPD2 were found, and several independent losses and incomplete concerted evolution were inferred. The among-site rate variation was significantly lower in the RNA polymerase introns than in the rps16 intron and ITSs, a property that is attractive in phylogenetic analyses.

Molecular cloning and characterization of norcoclaurine synthase, an enzyme catalyzing the first committed step in benzylisoquinoline alkaloid biosynthesis

(S)-Norcoclaurine synthase (NCS) (EC 4.2.1.78) catalyzes the condensation of 3,4-dihydroxyphenylethylamine (dopamine) and 4-hydroxyphenylacetaldehyde (4-HPAA) as the first committed step in the biosynthesis of benzylisoquinoline alkaloids such as morphine, sanguinarine, and berberine, in plants. A molecular clone encoding NCS was isolated from a meadow rue (Thalictrum flavum ssp. glaucum) cell suspension culture cDNA library. Heterologous expression of the NCS cDNA, truncated to remove a putative signal peptide, produced a recombinant protein with NCS activity. Recombinant NCS showed sigmoidal saturation kinetics for dopamine (Hill coefficient=1.98), hyperbolic saturation kinetics for 4-HPAA (Km of 700 microm), and pH and temperature optima of 7.0 and 40 degrees C, respectively, all similar to the purified, plant-derived enzyme. NCS exhibits 28-38% identity, and putative structural homology, with the Bet v 1 allergen and pathogenesis-related (PR)10 protein families. NCS also displays 35% identity with the enzyme (HYP1) responsible for hypericin biosynthesis in St John's wort (Hypericum perforatum). The novel catalytic functions of NCS and HYP1 define a new class of plant secondary metabolic enzymes within the Bet v 1 and PR10 protein families. Weaker homology was also detected between NCS and proteins identified in the latex of Papaver somniferum (opium poppy), and in Arabidopsis thaliana. A family of three to five NCS genes is abundantly expressed in the rhizome, followed by petioles and roots of T. flavum. NCS transcripts were localized to the immature endodermis and pericycle in roots, and the protoderm of leaf primordia in rhizomes; thus, the sites of NCS gene expression and berberine accumulation are temporally and spatially separated in roots and rhizomes respectively.

Phylogeny of Panax using chloroplast trnC-trnD intergenic region and the utility of trnC-trnD in interspecific studies of plants

Sequences of the chloroplast trnC-trnD region and the internal transcribed spacer (ITS) regions of nuclear ribosomal DNA were obtained for all species of Panax L. (the ginseng plant genus, Araliaceae) to reconstruct phylogenetic relationships. The trnC-trnD phylogeny is congruent with the ITS phylogeny for the diploid taxa of Panax. This study is the first use of the trnC-trnD sequence data for phylogenetic analysis at the interspecific level. We evaluated this DNA region for its phylogenetic utility at the lower taxonomic level for flowering plants. The trnC-trnD region includes the trnC-petN intergenic spacer, the petN gene, the petN-psbM intergenic spacer, the psbM gene, and the psbM-trnD intergenic spacer. The petN and psbM genes are small, 90 and 104-114 bp across angiosperms, respectively, and have conserved sequences. We have designed universal amplification and sequencing primers within these two genes. Using these primers, we have successfully amplified the entire trnC-trnD region for a diversity of flowering plant groups, including Aralia L. (Araliaceae), Calycanthus L. (Calycanthaceae), Corylus L. (Betulaceae), Hamamelis L. (Hamamelidaceae), Hydrocotyle L. (Apiaceae), Illigera Blume (Hernandiaceae), Nelumbo Adans. (Nelumbonaceae), Nolana L. ex L.f. (Solanaceae), Prunus L. (Rosaceae), and Staphylea L. (Staphyleaceae). In Panax, the trnC-trnD region provides a similar number of informative phylogenetic characters as the ITS regions and a slightly higher number of informative characters than the chloroplast ndhF gene. We thus demonstrate the utility of the trnC-trnD region for lower-level phylogenetic studies in flowering plants.

Lab scale and medium scale production of recombinant allergens in Escherichia coli

Recombinant products have become invaluable tools for diagnostic as well as therapeutic purposes in modern medicine. Especially in cases where raw naturally derived products are difficult to standardize, well-defined recombinant single components represent the matter of choice. In the recent past, much effort has been undertaken to define individual proteins derived from various sources like pollen, spores of moulds, pet dander, and food causing Type 1 allergic reactions in humans. Therefore, methods for cloning, sequencing, and expressing cDNAs coding for allergens in Escherichia coli became of great interest to allergologists. For the recombinant production of allergens, suitable expression systems, growing conditions, and purification steps have to be established for each individual product. Finally, the purified recombinant allergen has to be carefully investigated for the biochemical, biophysical, and immunological properties. In the following paper, several prokaryotic expression systems, purification strategies, and analytical methods will be presented and pitfalls discussed.

Evolutionary implications of infra- and interspecific molecular variability of pathogenesis-related proteins

We have examined phylogenetic relationships in seven pathogenesis-related (PR) protein families. Within-family comparisons involved 79 species, 166 amino acid sequences, and 1,791 sites. For 37 species, 124 different PR isoforms were identified (an average of 3.3 per species). Thirty-one of the 37 species investigated tended to cluster together (84%). Of the 17 clusters distinguished in the seven phylogenetic trees, 10 (59%) were in agreement with their taxonomic status, ascertained at the family level. The strong similarities among the intraspecific forms, as compared to interspecific differences, argue for some kind of gene conversion, but the rare occurrence of widely different isoforms also suggests diversifying selection. PRs 1, 6, and 4 seem to be less differentiated than PRs 3, 2, 10, and 5.

[Cross-reactivity between fruit and vegetables]

Vegetable foods are the most frequent cause of food allergy after the age of 5 years. The most commonly implicated foods are fruit and dried fruits, followed in Spain by legumes and fresh garden produce. In patients allergic to fruit and garden produce, multiple sensitizations to other vegetable products, whether from the same family or taxonomically unrelated, are frequent, although they do not always share the same clinical expression. Furthermore, more than 75 % of these patients are allergic to pollen, the type of pollen varying in relation to the aerobiology of the area. The basis of these associations among vegetable foods and with pollens lies in the existence of IgE antibodies against "panallergens", which determines cross-reactivity. Panallergens are proteins that are spread throughout the vegetable kingdom and are implicated in important biological functions (generally defense) and consequently their sequences and structures are highly conserved. The three best-known groups are allergens homologous to Bet v 1, profilins, and lipid transfer proteins (LTP). Allergens homologous to Bet v 1 (major birch pollen allergen) constitute a group of defense proteins (PR-10), with a molecular weight of 17 kDa, which behave as major allergens in patients from northern and central Europe with allergy to vegetables associated with birch pollen allergy. In these patients, the primary sensitization seems to be produced through the inhalation route on exposure to birch pollen. The symptomatology characteristically associated with sensitization to this family of allergens is oral allergy syndrome (OAS). Profilins are highly conserved proteins in all eukaryotic organisms and are present in pollen and a wide variety of vegetable foods. They have a molecular weight of 14 kDa and present a high degree of structural homology as well as marked cross-reactivity among one another. The presence of anti-profilin IgE broadens the spectrum of sensitizations to vegetable foods detected through skin tests and/or in vitro tests but whether it correlates with the clinical expression of food allergy is unclear.LTPs are the most commonly implicated allergens in allergy to Rosaceae fruits in patients from the Mediterranean area without birch pollen sensitization. LTPs are a family of 9kDA polypeptides, widely found in the vegetable kingdom and implicated in cuticle formation and defense against pathogens (PR-14). They are thermostable and resistant to pepsin digestion, which makes them potent food allergens and explains the frequent development of systemic symptoms (urticaria, anaphylaxis) in patients allergic to Rosaceae fruits in Spain. LTPs have also been identified in other vegetable foods and in pollens and a marked degree of cross-reactivity among them has been demonstrated, which may explain (together with profilin) the frequency of individuals sensitized to vegetable foods in the Mediterranean area.

Crystal structure of a hypoallergenic isoform of the major birch pollen allergen Bet v 1 and its likely biological function as a plant steroid carrier

Bet v 1l is a naturally occurring hypoallergenic isoform of the major birch pollen allergen Bet v 1. The Bet v 1 protein belongs to the ubiquitous family of pathogenesis-related plant proteins (PR-10), which are produced in defense-response to various pathogens. Although the allergenic properties of PR-10 proteins have been extensively studied, their biological function in plants is not known. The crystal structure of Bet v 1l in complex with deoxycholate has been determined to a resolution of 1.9A using the method of molecular replacement. The structure reveals a large hydrophobic Y-shaped cavity that spans the protein and is partly occupied by two deoxycholate molecules which are bound in tandem and only partially exposed to solvent. This finding indicates that the hydrophobic cavity may have a role in facilitating the transfer of apolar ligands. The structural similarity of deoxycholate and brassinosteroids (BRs) ubiquitous plant steroid hormones, prompted the mass spectrometry (MS) study in order to examine whether BRs can bind to Bet v 1l. The MS analysis of a mixture of Bet v 1l and BRs revealed a specific non-covalent interaction of Bet v 1l with brassinolide and 24-epicastasterone. Together, our findings are consistent with a general plant-steroid carrier function for Bet v 1 and related PR-10 proteins. The role of BRs transport in PR-10 proteins may be of crucial importance in the plant defense response to pathological situations as well as in growth and development.

Birch PR-10c is induced by factors causing oxidative stress but appears not to confer tolerance to these agents

•  Expression of all known and newly found pathogenesis-related PR-10 proteins (PR-10a, b, c, d, e) was analysed from Cu-sensitive and -tolerant birch clones to find out whether they follow the same expression pattern. The relationship of PR-10 proteins, particularly PR-10c, to oxidative stress caused by metals or ozone was studied in tolerant and sensitive birch clones to find out possible linkages to tolerance. •  Antibody developed to PR-10c was used in Western blot analysis. Other PR-10 proteins were studied with two-dimensional electrophoresis and mass spectrometry. Metal-sensitive yeasts were transformed with PR-10c. •  Two new members of PR-10 family, PR-10d and PR-10e, were found. Various PR-10 proteins showed different expression patterns. The amount of PR-10c increased with increasing soil metal concentrations but was, in general, more prominent in Cu-sensitive than in Cu-tolerant clones. PR-10c did not alter metal tolerance in metal-sensitive yeasts. •  The PR-10c protein appears not to confer metal- or ozone-tolerance in birch. However, this does not exclude the possibility that it is involved in the tolerance or sensitivity mechanism in an indirect manner.

IgE-mediated food allergy--extensive review of the literature

Adverse reactions to food, i.e. food allergy and intolerance have gained considerable attention. This overview focuses on the diagnosis and management of IgE-mediated food allergy that is believed to be responsible for most immediate-type food-induced hypersensitivity reactions. Clinically, these reactions are characterised by a variety of signs and symptoms that occur within minutes or hours after consumption of the offending food. Reactions may be limited or more generalised with involvement of the skin, nose, eyes, and/or lungs. In more severe cases, cardiovascular symptoms including hypotension, shock, cardiac dysrhythmias and death can occur. In food-allergic individuals, IgE is produced against naturally occurring food components, primarily glycoproteins that usually retain their allergenicity after heating and/or proteolysis. While adults tend to be allergic to fish, crustaceans, peanuts and tree nuts, children tend to be allergic to cow's milk, egg white, wheat and soy more frequently. "Emerging" food allergens include tropical fruits, sesame seeds, psyllium, spices and condiments. These allergies frequently represent a cross-allergy to an allergen derived from another source, e.g. pollens or natural rubber latex. The evaluation of IgE-mediated food allergy relies on a careful history, physical examination, appropriate skin testing or in vitro testing with food extracts, and/or double blind, placebo-controlled food challenges. Avoidance remains the mainstay of therapy. However, allergens may be "hidden" and labelling can be non-precise or misleading, thereby severely hampering prevention. Patients with severe allergies should keep at hand an emergency kit with adrenaline, an antihistamine and an injectable rapid onset-of-action corticosteroid. At present there is no evidence to support the use of immunotherapy, except for research purposes. Production of "hypoallergenic" food is hampered by incomplete methods for assessing the allergenic potential of such novel foods.

Anaphylaxis to camomile: clinical features and allergen cross-reactivity

BACKGROUND

Medicinal remedies of plant origin became very popular in recent years, and allergic reactions to these are on the rise, accordingly. Camomile has been reported as a potential trigger of severe anaphylaxis. The allergens responsible for camomile allergy have not been characterized as yet.

OBJECTIVE

The present study aims at reviewing the clinical symptomatology of immediate-type reactions in a series of patients sensitized to camomile and at characterizing the responsible allergens.

METHODS

Fourteen patients with a history of allergy either to camomile or to spices or weeds, and a positive skin prick test/RAST to camomile were investigated for related allergic reactions to food, pollen and others. IgE-binding patterns were determined by immunoblotting, inhibition tests and deglycosylation experiments.

RESULTS

Ten of 14 patients had a clinical history of immediate-type reactions to camomile, in some cases life threatening. Eleven subjects were also sensitized to mugwort in prick or RAST, eight to birch tree pollen. Using a polyclonal rabbit anti-Bet v 1 antibody, a homologue of the major birch pollen allergen Bet v 1 was detected in two camomile blots. In four cases a group of higher molecular weight allergens (23-50 kDa) showed IgE-binding to camomile. All allergens proved heat stable. Binding was inhibited in variable degrees by extracts from celery roots, anize seeds and pollen from mugwort, birch and timothy grass. Deglycosylation experiments proved the presence of carbohydrate determinants in camomile which were not responsible for IgE-binding, though. Profilins (Bet v 2) were not detected in our camomile extracts.

CONCLUSION

Incidence and risk of type I allergy to camomile may be underestimated. Concurrent sensitization to mugwort and birch pollen is not infrequent. Bet v 1 and noncarbohydrate higher molecular weight proteins were found to be eliciting allergens and are responsible for cross-reactivity with other foods and pollen.

Molecular and biochemical classification of plant-derived food allergens

Molecular biology and biochemical techniques have significantly advanced the knowledge of allergens derived from plant foods. Surprisingly, many of the known plant food allergens are homologous to pathogenesis-related proteins (PRs), proteins that are induced by pathogens, wounding, or certain environmental stresses. PRs have been classified into 14 families. Examples of allergens homologous to PRs include chitinases (PR-3 family) from avocado, banana, and chestnut; antifungal proteins such as the thaumatin-like proteins (PR-5) from cherry and apple; proteins homologous to the major birch pollen allergen Bet v 1 (PR-10) from vegetables and fruits; and lipid transfer proteins (PR-14) from fruits and cereals. Allergens other than PR homologs can be allotted to other well-known protein families such as inhibitors of alpha-amylases and trypsin from cereal seeds, profilins from fruits and vegetables, seed storage proteins from nuts and mustard seeds, and proteases from fruits. As more clinical data and structural information on allergenic molecules becomes available, we may finally be able to answer what characteristics of a molecule are responsible for its allergenicity.

Allergen mimotopes in food enhance type I allergic reactions in mice

BIP1is a murine IgG antibody capable of enhancing the IgE binding to Bet v 1, the major birch pollen allergen. We have previously generated a mimotope of BIP1, designated Bet mim 1, from a constrained phage display peptide library. We demonstrated that oral immunization of BALB/c mice with the Bet mim 1 mimotope resulted in the induction of Bet v 1-specific IgG. The aim of this study was to test the influence of such an oral immunization with Bet mim 1 on a subsequent type I allergic response to Bet v 1. Phages displaying Bet mim 1 or control mimotopes, or PBS alone, were delivered to BALB/c mice by intragastric gavages prior to systemic sensitization with recombinant Bet v 1 and Al(OH)(3), an adjuvant inducing preferentially IgE antibody responses. Only mice fed with Bet mim 1-phages displayed substantially enhanced type I allergic skin reactivity to Bet v 1, as compared to mice pretreated with control mimotopes or PBS. A gastric digestion assay indicated that Bet v 1 and its homologue from apple, Mal d 1, were degraded within seconds under physiological conditions. In contrast, phage-displayed mimotopes were resistant to digestion. Our data indicate that allergen mimics in the diet that resist digestion, can induce allergen specific IgG able to enhance an allergic response. We therefore conclude that sensitization via the oral route may represent a mechanism for aggravating type I allergic reactions, probably leading to an earlier onset of symptoms even at lower allergen dosage.

Molecular characterization of Dau c 1, the Bet v 1 homologous protein from carrot and its cross-reactivity with Bet v 1 and Api g 1

BACKGROUND

Up to 70% of patients with birch pollen allergy exhibit the so-called oral allergy syndrome, an IgE-mediated food allergy. The most frequent and therefore best characterized pollen-fruit syndrome is apple allergy in patients suffering from tree pollen-induced pollinosis. The occurrence of adverse reactions to proteins present in vegetables such as celery and carrots in patients suffering from pollen allergy has also been reported. cDNAs for Bet v 1 homologous proteins have been cloned from celery, apple and cherry. Objective The aim of the study was to identify Bet v 1 homologues from carrot (Daucus carota), to isolate the respective cDNA, to compare the IgE-binding capacity of the natural protein to the recombinant allergen and determine the cross-reactivity to Api g 1 and Bet v 1.

METHODS

Molecular characterization of the carrot allergen was performed using IgE-immunoblotting, cross-inhibition assays, N-terminal sequencing, PCR-based cDNA cloning and expression of the recombinant protein in Escherichia coli.

RESULTS

A 16-kDa protein from carrot was identified as a major IgE-binding component and designated Dau c 1. Sequencing corresponding cDNAs revealed three extremely similar sequences (Dau c 1.1, 1.2 and 1.3) with an open reading frame of 462 bp coding for 154 amino acid residues.

CONCLUSIONS

Purified recombinant Dau c 1.2 was tested in immunoblots displaying IgE-binding capacity comparable to its natural counterpart. Cross-inhibition assays verified the existence of common B-cell epitopes present on Dau c 1, Api g 1 as well as on Bet v 1.

Genomic characterization of members of the Bet v 1 family: genes coding for allergens and pathogenesis-related proteins share intron positions

Bet v 1, the major birch pollen allergen, is a member of a multigene family; a number of isoforms and homologous proteins from closely related species (alder, hazel and hornbeam) has been isolated and their cDNAs cloned and characterized. Genomic clones coding for Bet v 1 and homologues from apple and hazel were isolated and sequenced. Some of these clones contained intervening sequences. The exon-intron formation is highly conserved throughout this family of pathogenesis-related proteins in dicot plants and is also found in Aopr1 (Asparagus officinalis), a monocol species. Phylogenetic analysis suggested a possible common origin of the intron position in these homologous proteins at codon 62 in various families of flowering plants, including Fagaceae, Rosaceae and Apiaceae. This conserved 'proto-splice site' may point to a structure/function relationship. A conserved sequence motif (P-loop) was also found in all members of this protein family. Moreover, there is a certain degree of sequence similarity among the proteins derived from various species throughout the dicots and the only monocot examined. This fact is reflected by cross-reactivity from monoclonal and polyclonal antibodies raised against Bet v 1.