Plant food allergens can be classified into families and superfamilies on the basis of their structural and functional properties. The most widespread groups of plant proteins that contain allergens are the cupin and prolamin superfamilies and the protein families of the plant defense system. The cupin superfamily includes allergenic seed storage proteins of the vicilin and legumin type present in soybeans, peanuts, and tree nuts. The prolamin superfamily includes several important types of allergens of legumes, tree nuts, cereals, fruits, and vegetables, such as the 2S albumin seed storage proteins, the nonspecific lipid transfer proteins, and the cereal α-amylase and protease inhibitors. Plant food allergens are also found among the various groups of defense proteins that enable plants to resist biotic and abiotic stress, such as the pathogenesis-related proteins, certain proteases, and protease inhibitors. This review focuses on a classification system of plant food allergens that is emerging from the synopsis of allergology and protein evolution.

https://www.jacionline.org/article/S0091-6749(04)00996-0/pdf

A classification of plant food allergens.

International consensus has been reached on the principles regarding evaluation of the food safety of genetically modified plants The concept of substantial equivalence has been developed as part of a safety evaluation framework, based on the idea that existing foods can serve as a basis for comparing the properties of genetically modified foods with the appropriate counterpart Application of the concept is not a safety assessment per se, but helps to identify similarities and differences between the existing food and the new product, which are then subject to further toxicological investigation Substantial equivalence is a starting point in the safety evaluation, rather than an endpoint of the assessment Consensus on practical application of the principle should be further elaborated Experiences with the safety testing of newly inserted proteins and of whole genetically modified foods are reviewed, and limitations of current test methodologies are discussed The development and validation of new profiling methods such as DNA microarray technology, proteomics, and metabolomics for the identification and characterization of unintended effects, which may occur as a result of the genetic modification, is recommended The assessment of the allergenicity of newly inserted proteins and of marker genes is discussed An issue that will gain importance in the near future is that of post-marketing surveillance of the foods derived from genetically modified crops It is concluded, among others that, that application of the principle of substantial equivalence has proven adequate, and that no alternative adequate safety assessment strategies are available

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1365-313X.2001.01119.x

Assessment of the food safety issues related to genetically modified foods

The basic leucine (Leu) zipper (bZIP) proteins compose a family of transcriptional regulators present exclusively in eukaryotes. The bZIP proteins characteristically harbor a bZIP domain composed of two structural features: a DNA-binding basic region and the Leu zipper dimerization region. They have been shown to regulate diverse plant-specific phenomena, including seed maturation and germination, floral induction and development, and photomorphogenesis, and are also involved in stress and hormone signaling. We have identified 89 bZIP transcription factor-encoding genes in the rice (Oryza sativa) genome. Their chromosomal distribution and sequence analyses suggest that the bZIP transcription factor family has evolved via gene duplication. The phylogenetic relationship among rice bZIP domains as well as with bZIP domains from other plant bZIP factors suggests that homologous bZIP domains exist in plants. Similar intron/exon structural patterns were observed in the basic and hinge regions of their bZIP domains. Detailed sequence analysis has been done to identify additional conserved motifs outside the bZIP domain and to predict their DNA-binding site specificity as well as dimerization properties, which has helped classify them into different groups and subfamilies, respectively. Expression of bZIP transcription factor-encoding genes has been analyzed by full-length cDNA and expressed sequence tag-based expression profiling. This expression profiling was complemented by microarray analysis. The results indicate specific or coexpression patterns of rice bZIP transcription factors starting from floral transition to various stages of panicle and seed development. bZIP transcription factor-encoding genes in rice also displayed differential expression patterns in rice seedlings in response to abiotic stress and light irradiation. An effort has been made to link the structure and expression pattern of bZIP transcription factor-encoding genes in rice to their function, based on the information obtained from our analyses and earlier known results. This information will be important for functional characterization of bZIP transcription factors in rice.

Genomic survey and gene expression analysis of the basic leucine zipper transcription factor family in rice.

This article provides a science-based, decision tree approach to assess the allergenic concerns associated with the introduction of gene products into new plant varieties. The assessment focuses on the source from which the transferred gene was derived. Sources fall into three general categories: common allergenic food proteins; less common allergenic foods or other known allergen sources; and sources with no history of allergenicity. Information concerning the amino acid sequence identity to known allergenic proteins, in vitro and/or in vivo immunologic assays, and assessment of key physiochemical properties are included in reaching a recommendation on whether food derived from the genetically modified plant variety should be labeled as to the source of the transferred gene. In the end, a balanced judgement of all the available data generated during allergenicity assessment will assure the safety of foods derived from genetically engineered crops. Using the approaches described here, new plant varieties generated by genetic modification should be introduced into the marketplace with the same confidence that new plant varieties developed by traditional breeding have been introduced for decades.

Assessment of the allergenic potential of foods derived from genetically engineered crop plants

Genomic Survey and Gene Expression Analysis of the Basic Leucine Zipper Transcription Factor Family

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2896%2900773-9

Reduction of 14–16 kDa allergenic proteins in transgenic rice plants by antisense gene

A 33-kDa allergen from rice (Oryza sativa L. Japonica). cDNA cloning, expression, and identification as a novel glyoxalase I.

Five proteins of 14−16 kDa (I−V), with cross-reactivity with antibodies specific for a previously isolated 16-kDa allergen, were purified from rice endosperm. The N-terminal amino acid sequences of...

Rice (Oryza sativa L.) α-Amylase Inhibitors of 14−16 kDa Are Potential Allergens and Products of a Multigene Family

Cloning of the rice seed α-globulin-encoding gene: sequence similarity of the 5'-flanking region to those of the genes encoding wheat high-molecular-weight glutenin and barley D hordein

Many plant basic leucine-zipper (bZIP) proteins have been isolated several of which have been shown to play a role in seed-specific gene expression. We isolated a novel bZIP protein (REB) gene encoding 425 amino acid residues from rice endosperm, which is similar to Opaque-2 heterodimerizing protein (OHP) of maize. The gene product, termed REB, contains Pro- and Gly-rich regions at its N terminus, followed by the typical basic and leucine-repeat regions. Recombinant REB binds to the region from -754 to -562 in the α-globulin gene promoter, but not to promoters of other major storage genes such as glutelin, prolamin and albumin. The 5′ region of the α-globulin gene possesses three binding sites for REB, which were determined as GCCACGT(A/C)AG, by using synthetic oligonucleotides. A Super-shift assay using anti-REB antibody suggested that REB is a major DNA-binding protein for the α-globulin gene promoter in rice endosperm.

Masayuki Nakase

Papers

Reduction of 14–16 kDa allergenic proteins in transgenic rice plants by antisense gene

A 33-kDa allergen from rice (Oryza sativa L. Japonica). cDNA cloning, expression, and identification as a novel glyoxalase I.

Rice (Oryza sativa L.) α-Amylase Inhibitors of 14−16 kDa Are Potential Allergens and Products of a Multigene Family

Cloning of the rice seed α-globulin-encoding gene: sequence similarity of the 5'-flanking region to those of the genes encoding wheat high-molecular-weight glutenin and barley D hordein

Characterization of a novel rice bZIP protein which binds to the alpha-globulin promoter.