Wheat non-specific lipid transfer protein genes display a complex pattern of expression in developing seeds

Diversity of Cationic Antimicrobial Peptides in Black Cumin (Nigella sativa L.) Seeds

Black cumin (Nigella sativa L.) is known to possess a wide variety of antimicrobial peptides belonging to different structural families. Three novel antimicrobial peptides have been isolated from black cumin seeds. Two of them were attributed as members of the non-specific lipid transfer proteins family, and one as a defensin. We have made an attempt of using the proteomic approach for novel antimicrobial peptides search in N. sativa seeds as well. The use of a well-established approach that includes extraction and fractionation stages remains relevant even in the case of novel peptides search because of the lacking N. sativa genome data. Novel peptides demonstrate a spectrum of antimicrobial activity against plant pathogenic organisms that may cause economically important crop diseases. These results obtained allow considering these molecules as candidates to be applied in "next-generation" biopesticides development for agricultural use.

TMT proteomics analysis of a pseudocereal crop, quinoa (Chenopodium quinoa Willd.), during seed maturation

Quinoa (Chenopodium quinoa Willd.), an Andean native crop, is increasingly popular around the world due to its high nutritional content and stress tolerance. The production and the popularity of this strategic global food are greatly restricted by many limiting factors, such as seed pre-harvest sprouting, bitter saponin, etc. To solve these problems, the underlying mechanism of seed maturation in quinoa needs to be investigated. In this study, based on the investigation of morphological characteristics, a quantitative analysis of its global proteome was conducted using the combinational proteomics of tandem mass tag (TMT) labeling and parallel reaction monitoring (PRM). The proteome changes related to quinoa seed maturation conversion were monitored to aid its genetic improvement. Typical changes of morphological characteristics were discovered during seed maturation, including mean grain diameter, mean grain thickness, mean hundred-grain weight, palea, episperm color, etc. With TMT proteomics analysis, 581 differentially accumulated proteins (DAPs) were identified. Functional classification analysis and Gene Ontology enrichment analysis showed that most DAPs involved in photosynthesis were downregulated, indicating low levels of photosynthesis. DAPs that participated in glycolysis, such as glyceraldehyde-3-phosphate dehydrogenase, pyruvate decarboxylase, and alcohol dehydrogenase, were upregulated to fulfill the increasing requirement of energy consumption during maturation conversion. The storage proteins, such as globulins, legumins, vicilins, and oleosin, were also increased significantly during maturation conversion. Protein-protein interaction analysis and function annotation revealed that the upregulation of oleosin, oil body-associated proteins, and acyl-coenzyme A oxidase 2 resulted in the accumulation of oil in quinoa seeds. The downregulation of β-amyrin 28-oxidase was observed, indicating the decreasing saponin content, during maturation, which makes the quinoa "sweet". By the PRM and qRT-PCR analysis, the expression patterns of most selected DAPs were consistent with the result of TMT proteomics. Our study enhanced the understanding of the maturation conversion in quinoa. This might be the first and most important step toward the genetic improvement of quinoa.

Tomato Allergy: The Characterization of the Selected Allergens and Antioxidants of Tomato (Solanum lycopersicum)-A Review

Tomatoes are one of the most broadly produced and consumed crop plants. They are the source of health-promoting nutrients such as antioxidants, including ascorbic acid, polyphenols, or carotenoids. Despite the beneficial role of tomatoes in the daily diet, they have been confirmed as one of the most prevalent allergenic vegetables. Food allergies can cause many clinical symptoms, e.g., in the gastrointestinal tract, skin, and lungs, as well as anaphylactic shock. A huge amount of clinical research has been carried out to improve the understanding of the immunological mechanisms that lead to the lack of tolerance of food antigens, which can result in either immunoglobulin E (IgE)-mediated reactions or non-IgE-mediated reactions. Lifestyle and diet play an important role in triggering food allergies. Allergy to tomatoes is also linked to other allergies, such as grass pollen and latex allergy. Numerous attempts have been made to identify and characterize tomato allergens; however, the data available on the subject are not sufficient.

Characteristics, expression profile, and function of non-specific lipid transfer proteins of Populus trichocarpa

Plant non-specific lipid transfer proteins (nsLTPs) are involved in various physiological processes. However, the characteristics and function of LTPs in Populus trichocarpa are unclear. Here, we report the functional properties of type IV, V, and VI P. trichocarpa nsLTPs (PtLTPs). The IV, V, and VI PtLTPs clustered in the same clade shared similar gene structures and motif and distributions. Also, collinearity analysis revealed 2 and 7 gene pairs have tandem duplication and segmental duplication events, respectively. The expression patterns of type IV, V, and VI PtLTPs differed among poplar tissues. We investigated the effects of various stresses on the Potri.010G100600, Potri.010G196300, and Potri.016G104300 (type V LTPs) mRNA levels, and type V LTPs can respond to multiple stresses. Potri.008G061800 was localized to the cell wall, extracellular space, and plasma membrane. Glutathione-S-transferase-Potri.008G061800 obtained by prokaryotic expression had weakly inhibited the growth of Septotis populiperda in vitro. Taken together, our data show that type IV, V, and VI PtLTPs may be thought as novel regulators of plant stresses. They could be considered an effective genetic resource for molecular breeding in poplar.

Lipid Transfer Proteins (LTPs)-Structure, Diversity and Roles beyond Antimicrobial Activity

Lipid transfer proteins (LTPs) are among the most promising plant-exclusive antimicrobial peptides (AMPs). They figure among the most challenging AMPs from the point of view of their structural diversity, functions and biotechnological applications. This review presents a current picture of the LTP research, addressing not only their structural, evolutionary and further predicted functional aspects. Traditionally, LTPs have been identified by their direct isolation by biochemical techniques, whereas omics data and bioinformatics deserve special attention for their potential to bring new insights. In this context, new possible functions have been identified revealing that LTPs are actually multipurpose, with many additional predicted roles. Despite some challenges due to the toxicity and allergenicity of LTPs, a systematic review and search in patent databases, indicate promising perspectives for the biotechnological use of LTPs in human health and also plant defense.

Genome-wide identification and expression profile under abiotic stress of the barley non-specific lipid transfer protein gene family and its Qingke Orthologues

BACKGROUND

Plant non-specific lipid transfer proteins (nsLTPs), a group of small, basic ubiquitous proteins to participate in lipid transfer, cuticle formation and stress response, are involved in the regulation of plant growth and development. To date, although the nsLTP gene family of barley (Hordeum vulgare L.) has been preliminarily identified, it is still unclear in the recently completed genome database of barley and Qingke, and its transcriptional profiling under abiotic stress has not been elucidated as well.

RESULTS

We identified 40 barley nsLTP (HvLTP) genes through a strict screening strategy based on the latest barley genome and 35 Qingke nsLTP (HtLTP) orthologues using blastp, and these LTP genes were divided into four types (1, 2, D and G). At the same time, a comprehensive analysis of the physical and chemical characteristics, homology alignment, conserved motifs, gene structure and evolution of HvLTPs and HtLTPs further supported their similar nsLTP characteristics and classification. The genomic location of HvLTPs and HtLTPs showed that these genes were unevenly distributed, and obvious HvLTP and HtLTP gene clusters were found on the 7 chromosomes including six pairs of tandem repeats and one pair of segment repeats in the barley genome, indicating that these genes may be co-evolutionary and co-regulated. A spatial expression analysis showed that most HvLTPs and HtLTPs had different tissue-specific expression patterns. Moreover, the upstream cis-element analysis of HvLTPs and HtLTPs showed that there were many different stress-related transcriptional regulatory elements, and the expression pattern of HvLTPs and HtLTPs under abiotic stress also indicated that numerous HvLTP and HtLTP genes were related to the abiotic stress response. Taken together, these results may be due to the differences in promoters rather than by genes themselves resulting in different expression patterns under abiotic stress.

CONCLUSION

Due to a stringent screening and comprehensive analysis of the nsLTP gene family in barley and Qingke and its expression profile under abiotic stress, this study can be considered a useful source for the future studies of nsLTP genes in either barley or Qingke or for comparisons of different plant species.

A Lipid Transfer Protein has Antifungal and Antioxidant Activity and Suppresses Fusarium Head Blight Disease and DON Accumulation in Transgenic Wheat

Trichothecene mycotoxins such as deoxynivalenol (DON) are virulence factors of Fusarium graminearum, which causes Fusarium head blight, one of the most important diseases of small grain cereals. We previously identified a nonspecific lipid transfer protein (nsLTP) gene, AtLTP4.4, which was overexpressed in an activation-tagged Arabidopsis line resistant to trichothecin, a type B trichothecene in the same class as DON. Here we show that overexpression of AtLTP4.4 in transgenic wheat significantly reduced F. graminearum growth in 'Bobwhite' and 'RB07' lines in the greenhouse and reduced fungal lesion size in detached leaf assays. Hydrogen peroxide accumulation was attenuated on exposure of transgenic wheat plants to DON, indicating that AtLTP4.4 may confer resistance by inhibiting oxidative stress. Field testing indicated that disease severity was significantly reduced in two transgenic 'Bobwhite' lines expressing AtLTP4.4. DON accumulation was significantly reduced in four different transgenic 'Bobwhite' lines expressing AtLTP4.4 or a wheat nsLTP, TaLTP3, which was previously shown to have antioxidant activity. Recombinant AtLTP4.4 purified from Pichia pastoris exhibited potent antifungal activity against F. graminearum. These results demonstrate that overexpression of AtLTP4.4 in transgenic wheat suppresses DON accumulation in the field. Suppression of DON-induced reactive oxygen species by AtLTP4.4 might be the mechanism by which fungal spread and mycotoxin accumulation are inhibited in transgenic wheat plants.

A triticale tapetal non-specific lipid transfer protein (nsLTP) is translocated to the pollen cell wall

A Triticeae type III non-specific lipid transfer protein (nsLTP) was shown for the first time to be translocated from the anther tapetum to the pollen cell wall. Two anther-expressed non-specific lipid transfer proteins (nsLTPs) were identified in triticale (× Triticosecale Wittmack). LTPc3a and LTPc3b contain a putative signal peptide sequence and eight cysteine residues in a C-Xn-C-Xn-CC-Xn-CXC-Xn-C-Xn-C pattern. These proteins belong to the type III class of nsLTPs which are expressed exclusively in the inflorescence of angiosperms. The level of LTPc3 transcript in the anther was highest at the tetrad and uninucleate microspore stages, and absent in mature pollen. In situ hybridization showed that LTPc3 was expressed in the tapetal layer of the developing triticale anther. The expression of the LTPc3 protein peaked at the uninucleate microspore stage, but was also found to be associated with the mature pollen. Accordingly, an LTPc3a::GFP translational fusion expressed in transgenic Brachypodium distachyon first showed activity in the tapetum, then in the anther locule, and later on the mature pollen grain. Altogether, these results represent the first detailed characterization of a Triticeae anther-expressed type III nsLTP with possible roles in pollen cell wall formation.

The progress of leaf rust research in wheat

Leaf rust (also called brown rust) in wheat, caused by fungal pathogen Puccinia triticina Erikss. (Pt) is one of the major constraints in wheat production worldwide. Pt is widespread with diverse population structure and undergoes rapid evolution to produce new virulent races against resistant cultivars that are regularly developed to provide resistance against the prevailing races of the pathogen. Occasionally, the disease may also take the shape of an epidemic in some wheat-growing areas causing major economic losses. In the recent past, substantial progress has been made in characterizing the sources of leaf rust resistance including non-host resistance (NHR). Progress has also been made in elucidating the population biology of Pt and the mechanisms of wheat-Pt interaction. So far, ∼80 leaf rust resistance genes (Lr genes) have been identified and characterized; some of them have also been used for the development of resistant wheat cultivars. It has also been shown that a gene-for-gene relationship exists between individual wheat Lr genes and the corresponding Pt Avr genes so that no Lr gene can provide resistance unless the prevailing race of the pathogen carries the corresponding Avr gene. Several Lr genes have also been cloned and their products characterized, although no Avr gene corresponding a specific Lr gene has so far been identified. However, several candidate effectors for Pt have been identified and functionally characterized using genome-wide analyses, transcriptomics, RNA sequencing, bimolecular fluorescence complementation (BiFC), virus-induced gene silencing (VIGS), transient expression and other approaches. This review summarizes available information on different aspects of the pathogen Pt, genetics/genomics of leaf rust resistance in wheat including cloning and characterization of Lr genes and epigenetic regulation of disease resistance.

Non-Specific Lipid Transfer Proteins in Triticum kiharae Dorof. et Migush.: Identification, Characterization and Expression Profiling in Response to Pathogens and Resistance Inducers

Non-specific lipid-transfer proteins (nsLTPs) represent a family of plant antimicrobial peptides (AMPs) implicated in diverse physiological processes. However, their role in induced resistance (IR) triggered by non-pathogenic fungal strains and their metabolites is poorly understood. In this work, using RNA-seq data and our AMP search pipeline, we analyzed the repertoire of nsLTP genes in the wheat Triticum kiharae and studied their expression in response to Fusarium oxysporum infection and treatment with the intracellular metabolites of Fusarium sambucinum FS-94. A total of 243 putative nsLTPs were identified, which were classified into five structural types and characterized. Expression analysis showed that 121 TkLTPs including sets of paralogs with identical mature peptides displayed specific expression patters in response to different treatments pointing to their diverse roles in resistance development. We speculate that upregulated nsLTP genes are involved in protection due to their antimicrobial activity or signaling functions. Furthermore, we discovered that in IR-displaying plants, a vast majority of nsLTP genes were downregulated, suggesting their role as negative regulators of immune mechanisms activated by the FS-94 elicitors. The results obtained add to our knowledge of the role of nsLTPs in IR and provide candidate molecules for genetic engineering of crops to enhance disease resistance.

Early Root Transcriptomic Changes in Wheat Seedlings Colonized by Trichoderma harzianum Under Different Inorganic Nitrogen Supplies

Wheat is one of the most important crops worldwide. The use of plant growth promoting microorganisms, such as those of the genus Trichoderma, constitutes an alternative to chemical fertilizers, since they are cheaper and are not detrimental to the environment. However, the interaction between Trichoderma and wheat plants has been scarcely studied, at least at a molecular level. In the present work, a microarray approach was used to study the early transcriptomic changes induced in wheat roots by Trichoderma harzianum, applied alone or in combination with different concentrations of calcium nitrate [Ca(NO₃)₂], which was last used as nitrogen (N) source. Our results show that T. harzianum causes larger transcriptomic changes than Ca(NO₃)₂ in wheat roots, and such changes are different when plants are challenged with Trichoderma alone or treated with a combination of T. harzianum and Ca(NO₃)₂. Overall, T. harzianum activates the expression of defense-related genes at early stages of the interaction with the roots, while this fungus reduces the expression of genes related to plant growth and development. Moreover, the current study in wheat roots, subjected to the different T. harzianum and Ca(NO₃)₂ combinations, reveals that the number of transcriptomic changes was higher when compared against those caused by the different Ca(NO₃)₂ concentrations than when it was compared against those caused by T. harzianum. N metabolism gene expression changes were in agreement with the levels of nitrate reductase activity measured in plants from Trichoderma plus Ca(NO₃)₂ conditions. Results were also concordant with plant phenotypes, which showed reduced growth at early interaction stages when inoculated with T. harzianum or with its combination with Ca(NO₃)₂ at the lowest dosage. These results were in a good agreement with the recognized role of Trichoderma as an inducer of plant defense.

Comprehensive classification of the plant non-specific lipid transfer protein superfamily towards its sequence-structure-function analysis

Background

Non-specific Lipid Transfer Proteins (nsLTPs) are widely distributed in the plant kingdom and constitute a superfamily of related proteins. Several hundreds of different nsLTP sequences—and counting—have been characterized so far, but their biological functions remain unclear. It has been clear for years that they present a certain interest for agronomic and nutritional issues. Deciphering their functions means collecting and analyzing a variety of data from gene sequence to protein structure, from cellular localization to the physiological role. As a huge and growing number of new protein sequences are available nowadays, extracting meaningful knowledge from sequence–structure–function relationships calls for the development of new tools and approaches. As nsLTPs show high evolutionary divergence, but a conserved common right handed superhelix structural fold, and as they are involved in a large number of key roles in plant development and defense, they are a stimulating case study for validating such an approach.

Methods

In this study, we comprehensively investigated 797 nsLTP protein sequences, including a phylogenetic analysis on canonical protein sequences, three-dimensional structure modeling and functional annotation using several well-established bioinformatics programs. Additionally, two integrative methodologies using original tools were developed. The first was a new method for the detection of (i) conserved amino acid residues involved in structure stabilization and (ii) residues potentially involved in ligand interaction. The second was a structure–function classification based on the evolutionary trace display method using a new tree visualization interface. We also present a new tool for visualizing phylogenetic trees.

Results

Following this new protocol, an updated classification of the nsLTP superfamily was established and a new functional hypothesis for key residues is suggested. Lastly, this work allows a better representation of the diversity of plant nsLTPs in terms of sequence, structure and function.

Purification and Characterization of a Nonspecific Lipid Transfer Protein 1 (nsLTP1) from Ajwain (Trachyspermum ammi) Seeds

Ajwain (Trachyspermum ammi) belongs to the family Umbelliferae, is commonly used in traditional, and folk medicine due to its carminative, stimulant, antiseptic, diuretic, antihypertensive, and hepatoprotective activities. Non-specific lipid transfer proteins (nsLTPs) reported from various plants are known to be involved in transferring lipids between membranes and in plants defense response. Here, we describe the complete primary structure of a monomeric non-specific lipid transfer protein 1 (nsLTP1), with molecular weight of 9.66 kDa, from ajwain seeds. The nsLTP1 has been purified by combination of chromatographic techniques, and further characterized by mass spectrometry, and Edman degradation. The ajwain nsLTP1 is comprised of 91 amino acids, with eight conserved cysteine residues. The amino acid sequence based predicted three dimensional (3D) structure is composed of four α-helices stabilized by four disulfide bonds, and a long C-terminal tail. The predicted model was verified by using different computational tools; i.e. ERRAT, verify 3D web server, and PROCHECK. The docking of ajwain nsLTP1 with ligands; myristic acid (MYR), and oleic acid (OLE) was performed, and molecular dynamics (MD) simulation was used to validate the docking results. The findings suggested that amino acids; Leu11, Leu12, Ala55, Ala56, Val15, Tyr59, and Leu62 are pivotal for the binding of lipid molecules with ajwain nsLTP1.

Identification and molecular characterization of allergenic non-specific lipid-transfer protein from durum wheat (Triticum turgidum)

BACKGROUND

Common wheat (Triticum aestivum) and durum wheat (T. turgidum) are both involved in Baker's asthma (BA) and food allergy (FA) including wheat-dependent exercise-induced asthma (WDEIA). However, allergens in durum wheat have not been described, and the over-expression of T. turgidum non-specific lipid-transfer protein (nsLTPs) is considered to increase resistance to phytopathogens.

OBJECTIVE

To identify and assess the allergenicity of nsLTP from T. turgidum.

METHODS

Recombinant T. turgidum nsLTP Tri tu 14 was generated and tested for structural integrity (circular dichroism-spectroscopy) and purity (SDS-PAGE). Thirty-two wheat allergic patients were enrolled: 20 Spanish patients (BA) with positive bronchial challenge to wheat flour, and 12 Italian patients (wheat FA/WDEIA) with positive double-blind placebo-controlled food challenge/open food challenge (OFC) to pasta. IgE values to wheat, Tri tu 14, Tri a 14 (T. aestivum) and Pru p 3 (P. persica) were determined by ImmunoCAP testing. Allergenic potency (in vitro mediator release) and IgE cross-reactivity were investigated.

RESULTS

Tri tu 14 was found to share 49% and 52% amino acid identity with Tri a 14 and Pru p 3, respectively. Among 25 Tri a 14 CAP positive sera, 23 (92%) were reactive to wheat extract, 22 (88%) to Tri tu 14 and 20 (80%) to Pru p 3. The correlation between Tri a 14 and Tri tu 14 specific IgE levels was r = 0.97 (BA) and r = 0.93 (FA/WDEIA), respectively. FA/WDEIA patients showed higher specific IgE values to Tri tu 14 and Pru p 3 than BA patients. Tri tu 14 displayed allergenic activity by mediator release from effector cells and IgE cross-reactivity with Pru p 3. The degree of IgE cross-reactivity between the two wheat nsLTPs varied between individual patients.

CONCLUSIONS AND CLINICAL RELEVANCE

Sensitization to Tri tu 14 likely appears to be more important in wheat FA/WDEIA than in BA. Over-expression of Tri tu 14 in wheat would represent a risk for patients with nsLTP-mediated FA.

Expression and characterization of a barley phosphatidylinositol transfer protein structurally homologous to the yeast Sec14p protein

Phosphatidylinositol transfer proteins (PITPs) include a large group of proteins implicated in the non-vesicular traffic of phosphatidylinositol (PI) between membranes. In yeast, the structure and function of the PITP Sec14-p protein have been well characterized. In contrast, the knowledge on plant PITP proteins is very scarce. In this work, we characterized a novel type of PITP protein in barley named HvSec14p and related to the yeast Sec14-p protein. Our data reveal that HvSec14p consists of only the Sec14p-domain structurally homologous to the yeast phosphoinositide binding domain. We show that HvSec14p expression is up-regulated at both transcript and protein levels at specific stages of development during seed formation and germination, and in leaves of a drought-tolerant barley genotype under osmotic constraints. Modeling analyses of the protein three-dimensional structure revealed its capacity to dock the phosphoinositides, PtdIns(3)P, PtdIns(4)P, PtdIns(5)P and PtdIns(3,5)P2. Consistently, the recombinant HvSec14p protein is able to bind in vitro most PIP types, the highest affinity being observed with PtdIns(3,5)P2. Based on the high gene expression at specific developmental stages and in drought-tolerant barley genotypes, we propose that HvSec14p plays essential roles in the biogenesis of membranes in expanding cells and in their preservation under osmotic stress conditions.

Alternative Oxidase Gene Family in Hypericum perforatum L.: Characterization and Expression at the Post-germinative Phase

Alternative oxidase (AOX) protein is located in the inner mitochondrial membrane and is encoded in the nuclear genome being involved in plant response upon a diversity of environmental stresses and also in normal plant growth and development. Here we report the characterization of the AOX gene family of Hypericum perforatum L. Two AOX genes were identified, both with a structure of four exons (HpAOX1, acc. KU674355 and HpAOX2, acc. KU674356). High variability was found at the N-terminal region of the protein coincident with the high variability identified at the mitochondrial transit peptide. In silico analysis of regulatory elements located at intronic regions identified putative sequences coding for miRNA precursors and trace elements of a transposon. Simple sequence repeats were also identified. Additionally, the mRNA levels for the HpAOX1 and HpAOX2, along with the ones for the HpGAPA (glyceraldehyde-3-phosphate dehydrogenase A subunit) and the HpCAT1 (catalase 1), were evaluated during the post-germinative development. Gene expression analysis was performed by RT-qPCR with accurate data normalization, pointing out HpHYP1 (chamba phenolic oxidative coupling protein 1) and HpH2A (histone 2A) as the most suitable reference genes (RGs) according to GeNorm algorithm. The HpAOX2 transcript demonstrated larger stability during the process with a slight down-regulation in its expression. Contrarily, HpAOX1 and HpGAPA (the corresponding protein is homolog to the chloroplast isoform involved in the photosynthetic carbon assimilation in other plant species) transcripts showed a marked increase, with a similar expression pattern between them, during the post-germinative development. On the other hand, the HpCAT1 (the corresponding protein is homolog to the major H2O2-scavenging enzyme in other plant species) transcripts showed an opposite behavior with a down-regulation during the process. In summary, our findings, although preliminary, highlight the importance to investigate in more detail the participation of AOX genes during the post-germinative development in H. perforatum, in order to explore their functional role in optimizing photosynthesis and in the control of reactive oxygen species (ROS) levels during the process.

Non-specific lipid transfer proteins in plants: presenting new advances and an integrated functional analysis

Plant non-specific lipid-transfer proteins (nsLTPs) are small, basic proteins present in abundance in higher plants. They are involved in key processes of plant cytology, such as the stablization of membranes, cell wall organization, and signal transduction. nsLTPs are also known to play important roles in resistance to biotic and abiotic stress, and in plant growth and development, such as sexual reproduction, seed development and germination. The structures of plant nsLTPs contain an eight-cysteine residue conserved motif, linked by four disulfide bonds, and an internal hydrophobic cavity, which comprises the lipid-binding site. This structure endows stability and increases the ability to bind and/or carry hydrophobic molecules. There is growing interest in nsLTPs, due to their critical roles, resulting in the need for a comprehensive review of their form and function. Relevant topics include: nsLTP structure and biochemical features, their classification, identification, and characterization across species, sub-cellular localization, lipid binding and transfer ability, expression profiling, functionality, and evolution. We present advances, as well as limitations and trends, relating to the different topics of the nsLTP gene family. This review collates a large body of research pertaining to the role of nsLTPs across the plant kingdom, which has been integrated as an in depth functional analysis of this group of proteins as a whole, and their activities across multiple biochemical pathways, based on a large number of reports. This review will enhance our understanding of nsLTP activity in planta, prompting further work and insights into the roles of this multifaceted protein family in plants.

On the role of a Lipid-Transfer Protein. Arabidopsis ltp3 mutant is compromised in germination and seedling growth

Plant Lipid-Transfer Proteins (LTPs) exhibit the ability to reversibly bind/transport lipids in vitro. LTPs have been involved in diverse physiological processes but conclusive evidence on their role has only been presented for a few members, none of them related to seed physiology. Arabidopsis seeds rely on storage oil breakdown to supply carbon skeletons and energy for seedling growth. Here, Arabidopsis ltp3 mutant was analyzed for its ability to germinate and for seedling establishment. Ltp3 showed delayed germination and reduced germination frequency. Seedling growth appeared reduced in the mutant but this growth restriction was rescued by the addition of an exogenous carbon supply, suggesting a defective oil mobilization. Lipid breakdown analysis during seedling growth revealed a differential profile in the mutant compared to the wild type. The involvement of LTP3 in germination and seedling growth and its relationship with the lipid transfer ability of this protein is discussed.

Changes in gene expression profiles as they relate to the adult plant leaf rust resistance in the wheat cv. Toropi

Leaf rust, caused by the foliar pathogen Puccinia triticina is a major disease of wheat in the southern region of Brazil and invariably impacts on production, being responsible for high yield losses. The Brazilian wheat cultivar Toropi has proven, durable adult plant resistance (APR) to leaf rust, which uniquely shows a pre-haustorial resistance phenotype. In this study we aimed to understand the interaction between P. triticina and the pre-haustorial APR in Toropi by quantitatively evaluating the temporal transcription profiles of selected genes known to be related to infection and defense in wheat. The expression profiles of 15 selected genes varied over time, grouping into six expression profile groups. The expression profiles indicated the induction of classical defence pathways in response to pathogen development, but also the potential modification of Toropi's cellular status for the benefit of the pathogen. Classical defence genes, including peroxidases, β-1,3-glucanases and an endochitinase were expressed both early (pre-haustorial) and late (post-haustorial) over the 72 h infection time course, while induction of transcription of other infection-related genes with a potential role in defence, although variable was maintained through-out. These genes directly or indirectly had a role in plant lignification, oxidative stress, the regulation of energy supply, water and lipid transport, and cell cycle regulation. The early induction of transcription of defence-related genes supports the pre-haustorial resistance phenotype in Toropi, providing a valuable source of genes controlling leaf rust resistance for wheat breeding.

A wheat lipid transfer protein 3 could enhance the basal thermotolerance and oxidative stress resistance of Arabidopsis

Wheat (Triticum aestivum L.) is one of the major grain crops, and heat stress adversely affects wheat production in many regions of the world. Previously, we found a heat-responsive gene named Lipid Transfer Protein 3 (TaLTP3) in wheat. TaLTP3 was deduced to be regulated by cold, ABA, MeJA, Auxin and oxidative stress according to cis-acting motifs in its promoter sequences. In this study, we show that TaLTP3 is responsive to prolonged water deficit, salt or ABA treatment in wheat seedlings. Also, TaLTP3 accumulation was observed after the plant suffered from heat stress both at the seedling and the grain-filling stages. TaLTP3 protein was localized in the cell membrane and cytoplasm of tobacco epidermal cells. Overexpression of TaLTP3 in yeast imparted tolerance to heat stress compared to cells expressing the vector alone. Most importantly, transgenic Arabidopsis plants engineered to overexpress TaLTP3 showed higher thermotolerance than control plants at the seedling stage. Further investigation indicated that transgenic lines decreased H₂O₂ accumulation and membrane injury under heat stress. Taken together, our results demonstrate that TaLTP3 confers heat stress tolerance possibly through reactive oxygen species (ROS) scavenging.

BraLTP1, a lipid transfer protein gene involved in epicuticular wax deposition, cell proliferation and flower development in Brassica napus

Plant non-specific lipid transfer proteins (nsLTPs) constitute large multigene families that possess complex physiological functions, many of which remain unclear. This study isolated and characterized the function of a lipid transfer protein gene, BraLTP1 from Brassica rapa, in the important oilseed crops Brassica napus. BraLTP1 encodes a predicted secretory protein, in the little known VI Class of nsLTP families. Overexpression of BnaLTP1 in B. napus caused abnormal green coloration and reduced wax deposition on leaves and detailed wax analysis revealed 17-80% reduction in various major wax components, which resulted in significant water-loss relative to wild type. BnaLTP1 overexpressing leaves exhibited morphological disfiguration and abaxially curled leaf edges, and leaf cross-sections revealed cell overproliferation that was correlated to increased cytokinin levels (tZ, tZR, iP, and iPR) in leaves and high expression of the cytokinin biosynthsis gene IPT3. BnaLTP1-overexpressing plants also displayed morphological disfiguration of flowers, with early-onset and elongated carpel development and outwardly curled stamen. This was consistent with altered expression of a a number of ABC model genes related to flower development. Together, these results suggest that BraLTP1 is a new nsLTP gene involved in wax production or deposition, with additional direct or indirect effects on cell division and flower development.

Lipid transfer proteins in coffee: isolation of Coffea orthologs, Coffea arabica homeologs, expression during coffee fruit development and promoter analysis in transgenic tobacco plants

The aim of the present study was to perform a genomic analysis of non-specific lipid-transfer proteins (nsLTPs) in coffee. Several nsLTPs-encoding cDNA and gene sequences were cloned from Coffea arabica and Coffea canephora species. In this work, their analyses revealed that coffee nsLTPs belong to Type II LTP characterized under their mature forms by a molecular weight of around 7.3 kDa, a basic isoelectric points of 8.5 and the presence of typical CXC pattern, with X being an hydrophobic residue facing towards the hydrophobic cavity. Even if several single nucleotide polymorphisms were identified in these nsLTP-coding sequences, 3D predictions showed that they do not have a significant impact on protein functions. Northern blot and RT-qPCR experiments revealed specific expression of Type II nsLTPs-encoding genes in coffee fruits, mainly during the early development of endosperm of both C. arabica and C. canephora. As part of our search for tissue-specific promoters in coffee, an nsLTP promoter region of around 1.2 kb was isolated. It contained several DNA repeats including boxes identified as essential for grain specific expression in other plants. The whole fragment, and a series of 5' deletions, were fused to the reporter gene β-glucuronidase (uidA) and analyzed in transgenic Nicotiana tabacum plants. Histochemical and fluorimetric GUS assays showed that the shorter (345 bp) and medium (827 bp) fragments of nsLTP promoter function as grain-specific promoters in transgenic tobacco plants.

Molecular dynamics simulations of barley and maize lipid transfer proteins show different ligand binding preferences in agreement with experimental data

Experimental studies of barley and maize lipid transfer proteins (LTPs) show that the two proteins bind the ligand palmitate in opposite orientations in their internal cavities. Moreover, maize LTP is reported to bind the ligand caprate in the internal cavity in a mixture of two orientations with approximately equal occupancy. Six 30 ns molecular dynamics (MD) simulations of maize and barley LTP with ligands bound in two orientations (modes M and B) have been used to understand the different ligand binding preferences. The simulations show that both maize and barley LTP could bind palmitate in the orientation observed experimentally for maize LTP (mode M), with the predominant interaction being a salt bridge between the ligand carboxylate headgroup and a conserved arginine side chain. However, the simulation of barley LTP with palmitate in the mode B orientation shows the most favorable protein-ligand interaction energy. In contrast, the simulations of maize LTP with palmitate and with caprate in the mode B orientation show no persistent ligand binding, the ligands leaving the cavity during the simulations. Sequence differences between maize and barley LTP in the AB loop region, in residues at the base of the hydrophobic cavity, and in the helix A region are identified as contributing to the different behavior. The simulations reproduce well the experimentally observed binding preferences for palmitate and suggest that the experimental data for maize LTP with caprate reflect ligand mobility in binding mode M rather than the population of binding modes M and B.

Purification and characterization of a novel antifungal protein with antiproliferation and anti-HIV-1 reverse transcriptase activities from Peganum harmala seeds

A novel antifungal protein, designated as PHP, was isolated from the seeds of Peganum harmala, by cationic exchange chromatography on Resource S column and gel filtration on Sephadex 75 10/300 GL column. PHP was found to form a homodimer of about 16 kDa. Isoelectric focusing polyacrylamide gel electrophoresis analysis showed that the isoelectric point of PHP was ∼8.4. The N-terminal 20-amino acid sequence of PHP, ITCPQVTQSLAPCVPYLISG, resembles the non-specific lipid transfer proteins in certain plants. PHP exhibited lipid-binding activity. Furthermore, PHP exerted antifungal activity against Alternaria alternate, Penicillium degitatum, Rhizopus stuolonifer, and Magnaporthe grisea, and its antifungal activity was stable in the temperature range 4-60°C, and in the pH range 4-10. It inhibited the mycelial growth in A. alternate, P. degitatum, R. stuolonifer, and M. grisea with 50% inhibitory concentration (IC(50)) of 1.5, 37.5, 8.44, and 12.19 μM, respectively. PHP was also able to inhibit the proliferation of esophagus carcinoma (Eca-109), cervical carcinoma (HeLa), gastric carcinoma (MGC-7), and melanoma (B16) cells with IC(50) of 0.7, 2.74, 3.13, and 1.47 μM, respectively. Moreover, PHP significantly inhibited HIV-1 reverse transcriptase (RT) with an IC(50) of 1.26 μM. It did not have hemagglutinating and antibacterial activities. In conclusion, a novel antifungal protein with antiproliferation and anti-HIV-1 RT activities was obtained from P. harmala seeds.

An extracellular lipid transfer protein is relocalized intracellularly during seed germination

Plant lipid transfer proteins (LTPs) constitute a family of small proteins recognized as being extracellular. In agreement with this notion, several lines of evidence have shown the apoplastic localization of HaAP10, a LTP from Helianthus annuus dry seeds. However, HaAP10 was recently detected intracellularly in imbibing seeds. To clarify its distribution, immunolocalization experiments were performed during the course of germination and confirmed its intracellular localization upon early seed imbibition. Further assays using a hydrophobic dye, FM4-64, inhibitors of vesicular traffic, and immunolocalization of the pectin rhamnogalacturonan-II, allowed the conclusion that endocytosis is activated as soon as seed imbibition starts. Furthermore, this study demonstrated that HaAP10 is endocytosed throughout imbibition. Biochemical and cellular approaches indicate that the intracellular fraction of this LTP appears associated with oil bodies and some evidence also suggest its presence in glyoxysomes. So, HaAP10 is apoplastic in dry seeds and upon imbibition is rapidly internalized and relocalized to organelles involved in lipid metabolism. The results suggest that HaAP10 may be acting as a fatty acid shuttle between the oil body and the glyoxysome during seed germination. This concept is consistent with the initial proposition that LTPs participate in the intracellular transfer of lipids which was further denied based on their apparent extracellular localization. This report reveals for the first time the relocalization of a lipid transfer protein and opens new perspectives on its role.

Computational study of ligand binding in lipid transfer proteins: Structures, interfaces, and free energies of protein-lipid complexes

Plant nonspecific lipid transfer proteins (nsLTPs) bind a wide variety of lipids, which allows them to perform disparate functions. Recent reports on their multifunctionality in plant growth processes have posed new questions on the versatile binding abilities of these proteins. The lack of binding specificity has been customarily explained in qualitative terms on the basis of a supposed structural flexibility and nonspecificity of hydrophobic protein-ligand interactions. We present here a computational study of protein-ligand complexes formed between five nsLTPs and seven lipids bound in two different ways in every receptor protein. After optimizing geometries in molecular dynamics calculations, we computed Poisson-Boltzmann electrostatic potentials, solvation energies, properties of the protein-ligand interfaces, and estimates of binding free energies of the resulting complexes. Our results provide the first quantitative information on the ligand abilities of nsLTPs, shed new light into protein-lipid interactions, and reveal new features which supplement commonly held assumptions on their lack of binding specificity.

Discovery, identification and comparative analysis of non-specific lipid transfer protein (nsLtp) family in Solanaceae

Plant non-specific lipid transfer proteins (nsLtps) have been reported to be involved in plant defense activity against bacterial and fungal pathogens. In this study, we identified 135 (122 putative and 13 previously identified) Solanaceae nsLtps, which are clustered into 8 different groups. By comparing with Boutrot’s nsLtp classification, we classified these eight groups into five types (I, II, IV, IX and X). We compared Solanaceae nsLtps with Arabidopsis and Gramineae nsLtps and found that (1) Types I, II and IV are shared by Solanaceae, Gramineae and Arabidopsis; (2) Types III, V, VI and VIII are shared by Gramineae and Arabidopsis but not detected in Solanaceae so far; (3) Type VII is only found in Gramineae whereas type IX is present only in Arabidopsis and Solanaceae; (4) Type X is a new type that accounts for 52.59% Solanaceae nsLtps in our data, and has not been reported in any other plant so far. We further built and compared the three-dimensional structures of the eight groups, and found that the major functional diversification within the nsLtp family could be predated to the monocot/dicot divergence, and many gene duplications and sequence variations had happened in the nsLtp family after the monocot/dicot divergence, especially in Solanaceae.

Expressional diversity of wheat nsLTP genes: evidence of subfunctionalization via cis-regulatory divergence

Previously, the wheat non-specific lipid transfer proteins (TaLTP), members of a small multigene family, were reported to evidence a complex pattern of expression regulation. In order to assess further the expression diversity of the TaLTP genes, we have attempted to evaluate their expression profiles in responses to abiotic stresses, using semi-quantitative RT-PCR. The expression profiles generated herein revealed that the TaLTP genes in group A evidenced highly similar responses against abiotic stresses, whereas differential expression patterns among genes in each group were also observed. A total of seven promoters were fused to a GUS reporter gene and the recombinants were introduced into Arabidopsis, while three promoters evidenced non-detectible GUS activity. The promoters of TaLTP1, TaLTP7, and TaLTP10 included in group A drove strong expressions during plant development with overlapping patterns, in large part, but also exhibited distinct expression pattern, thereby suggesting subfunctionalization processing over evolutionary time. However, only trace expression in cotyledons, young emerged leaves, and epidermal cell layers of flower ovaries was driven by the promoter of TaLTP3 of group B. These results indicate that their distinct physiological functions appear to be accomplished by a subfunctionalization process involving degenerative mutations in regulatory regions.

Transcript profiles of two wheat lipid transfer protein-encoding genes are altered during attack by Hessian fly larvae

A sequence encoding a putative type-1 lipid transfer protein from wheat (Triticum aestivum L. em Thell) was identified through 'GeneCalling', an mRNA profiling technology. The mRNA for the Hfr-LTP (Hessian fly-responsive lipid transfer protein) gene decreased in abundance (196-fold) in susceptible wheat plants over the first eight days of attack by virulent Hessian fly larvae (Mayetiola destructor Say). Hfr-LTP encodes a putative protein containing eight cysteine residues that are conserved among plant LTPs and are responsible for correct protein folding through formation of disulfide bridges. Twelve hydrophobic amino acids in addition to arginine, glycine, proline, serine, threonine and tyrosine, plus an LTP signature sequence were present in conserved positions. A highly conserved signal peptide sequence was also present. Although attack by one virulent larva was sufficient to cause a decrease in Hfr-LTP mRNA abundance, higher infestation levels led to near silencing of the gene. Hfr-LTP transcript levels were not affected by other biotic factors (feeding by bird cherry-oat aphid, Rhopalosiphum padi L., and fall armyworm larvae, Spodoptera frugiperda Smith) or abiotic factors tested (mechanical wounding or treatment with abscisic acid, methyl jasmonate, or salicylic acid). Comparison to a previously described Hessian fly-responsive wheat LTP gene, TaLTP3, confirmed an initial increase in TaLTP3 mRNA in resistant plants. However, when quantified through eight days after egg hatch, responsiveness to infestation level and a marked decrease in susceptible plant TaLTP3 mRNA abundance were detected, as was seen for Hfr-LTP. Possible functions of LTP gene products in wheat-Hessian fly interactions are discussed.

Recombinant lipid transfer protein Tri a 14: a novel heat and proteolytic resistant tool for the diagnosis of baker's asthma

BACKGROUND

Baker's asthma is an important occupational allergic disease. Wheat lipid transfer protein (LTP) Tri a 14 is a major allergen associated with wheat allergy. No panel of wheat recombinant allergens for component-resolved diagnosis of baker's asthma is currently available.

OBJECTIVE

To evaluate the potential role of recombinant Tri a 14 as a novel tool for the diagnosis of baker's asthma, and to test the heat and proteolytic resistance of the wheat LTP allergen.

METHODS

A cDNA encoding Tri a 14 was isolated and sequenced, the recombinant allergen produced in Pichia pastoris and purified by chromatographic methods. Physicochemical and immunological comparison of the natural and recombinant forms of Tri a 14 was carried out by N-terminal amino acid sequencing, matrix-assisted laser desorption/ionization mass spectrometry, circular dichroism (CD) analysis, IgE immunodetection, and specific IgE determination and ELISA-inhibition assays using a pool or individual sera from 26 patients with baker's asthma. Thermal denaturation and simulated gastrointestinal digestion of both Tri a 14 forms were checked by spectroscopic and electrophoretic methods, respectively, and biological activity by basophil activation test (BAT).

RESULTS

Natural and recombinant Tri a 14 were similarly folded, as indicated by their nearly identical CD spectra and heat denaturation profiles. A high interclass correlation coefficient (0.882) was found between specific IgE levels to both Tri a 14 proteins in individual sera from baker's asthma patients, but a slightly lower IgE-binding potency of rTri a 14 was detected by ELISA-inhibition assays. Natural and recombinant Tri a 14 elicited positive BAT in two and one out of three patients, respectively. Heat denaturation profiles and simulated gastrointestinal digestion assays indicated that Tri a 14 displayed a high heat and digestive proteolytic resistance, comparable to those of peach Pru p 3, the model food allergen of the LTP family.

CONCLUSIONS

Recombinant Tri a 14 is a potential tool for baker's asthma diagnosis, based on its physicochemical and immunological similarity with its natural counterpart. Wheat Tri a 14 shows a high thermal stability and resistance to gastrointestinal digestion.

Characterization and antifungal properties of wheat nonspecific lipid transfer proteins

This study simultaneously considered the phylogeny, fatty acid binding ability, and fungal toxicity of a large number of monocot nonspecific lipid transfer proteins (ns-LTP). Nine novel full-length wheat ns-LTP1 clones, all possessing coding sequences of 348 bp, isolated from abiotic- and biotic-stressed cDNA libraries from aerial tissues, exhibited highly conserved coding regions with 78 to 99 and 71 to 100% identity at the nucleotide and amino acid levels, respectively. Phylogenetic analyses revealed two major ns-LTP families in wheat. Eight wheat ns-LTP genes from different clades were cloned into the expression vector pPICZalpha and transformed into Pichia pastoris. Sodium dodecyl sulfate polyacrylamide gel electrophoresis, Western blotting, and in vitro lipid binding activity assay confirmed that the eight ns-LTP were all successfully expressed and capable of in vitro binding fatty acid molecules. A comparative in vitro study on the toxicity of eight wheat ns-LTP to mycelium growth or spore germination of eight wheat pathogens and three nonwheat pathogens revealed differential toxicities among different ns-LTP. Values indicating 50% inhibition of fungal growth or spore germination of three selected ns-LTP against six fungi ranged from 1 to 7 microM. In vitro lipid-binding activity of ns-LTP was not correlated with their antifungal activity. Using the fluorescent probe SYTOX Green as an indicator of fungal membrane integrity, the in vitro toxicity of wheat ns-LTP was associated with alteration in permeability of fungal membranes.

Genome-wide analysis of the rice and Arabidopsis non-specific lipid transfer protein (nsLtp) gene families and identification of wheat nsLtp genes by EST data mining

Background

Plant non-specific lipid transfer proteins (nsLTPs) are encoded by multigene families and possess physiological functions that remain unclear. Our objective was to characterize the complete nsLtp gene family in rice and arabidopsis and to perform wheat EST database mining for nsLtp gene discovery.

Results

In this study, we carried out a genome-wide analysis of nsLtp gene families in Oryza sativa and Arabidopsis thaliana and identified 52 rice nsLtp genes and 49 arabidopsis nsLtp genes. Here we present a complete overview of the genes and deduced protein features. Tandem duplication repeats, which represent 26 out of the 52 rice nsLtp genes and 18 out of the 49 arabidopsis nsLtp genes identified, support the complexity of the nsLtp gene families in these species. Phylogenetic analysis revealed that rice and arabidopsis nsLTPs are clustered in nine different clades. In addition, we performed comparative analysis of rice nsLtp genes and wheat (Triticum aestivum) EST sequences indexed in the UniGene database. We identified 156 putative wheat nsLtp genes, among which 91 were found in the 'Chinese Spring' cultivar. The 122 wheat non-redundant nsLTPs were organized in eight types and 33 subfamilies. Based on the observation that seven of these clades were present in arabidopsis, rice and wheat, we conclude that the major functional diversification within the nsLTP family predated the monocot/dicot divergence. In contrast, there is no type VII nsLTPs in arabidopsis and type IX nsLTPs were only identified in arabidopsis. The reason for the larger number of nsLtp genes in wheat may simply be due to the hexaploid state of wheat but may also reflect extensive duplication of gene clusters as observed on rice chromosomes 11 and 12 and arabidopsis chromosome 5.

Conclusion

Our current study provides fundamental information on the organization of the rice, arabidopsis and wheat nsLtp gene families. The multiplicity of nsLTP types provide new insights on arabidopsis, rice and wheat nsLtp gene families and will strongly support further transcript profiling or functional analyses of nsLtp genes. Until such time as specific physiological functions are defined, it seems relevant to categorize plant nsLTPs on the basis of sequence similarity and/or phylogenetic clustering.

Molecular genetics of puroindolines and related genes: regulation of expression, membrane binding properties and applications

Kernel texture of wheat is a primary determinant of its technological properties. Soft kernel texture phenotype results when the Puroindoline a and Puroindoline b genes are present and encode the wild-type puroindolines PINA and PINB, respectively, and various mutations in either or both gene(s) result in hard phenotypes. A wealth of information is now available that furthers our understanding regarding the spatial and temporal regulation of expression of Puroindoline genes. Through the use of model membranes and synthetic peptides we also have a clearer understanding of the significance of the cysteine backbone, the tryptophan-rich domain (TRD) and the helicoid tertiary structures of PIN proteins in relation to their membrane-active properties. Many studies suggest individual yet co-operative modes of action of the PIN proteins in determining kernel texture, and significant evidence is accumulating that the proteins have in vivo and in vitro antimicrobial activities, shedding light on the biological roles of this unique ensemble of proteins. The puroindolines are now being explored for grain kernel texture modifications as well as antimicrobial activities.

Wheat lipid transfer protein is a major allergen associated with baker's asthma

BACKGROUND

Baker's asthma is a frequent occupational allergic disorder mainly caused by inhalation of cereal flours. Lipid transfer proteins (LTPs) constitute a family of plant food panallergens, but their role as inhalant and wheat allergens is still unclear.

OBJECTIVE

We sought to explore the involvement of wheat LTPs in baker's asthma caused by wheat flour sensitization.

METHODS

Forty patients with occupational asthma caused by wheat flour inhalation were studied. Wheat LTP, Tri a 14, was purified by using a 2-step chromatographic protocol and characterized by N-terminal amino acid sequencing and 3-dimensional modeling. Its reactivity was confirmed by means of IgE immunodetection, ELISA and ELISA-inhibition assays, and skin prick tests.

RESULTS

Specific IgE to Tri a 14 was found in 60% of 40 individual sera from patients with baker's asthma, and the purified allergen elicited positive skin prick test reactions in 62% of 24 of these patients. Tri a 14 and peach LTP, Pru p 3, showed a sequence identity of 45%, but the low cross-reactivity between both allergens detected in several individual sera reflected great differences in their 3-dimensional IgE-binding regions.

CONCLUSIONS

Wheat LTP is a major inhalant allergen associated with baker's asthma caused by wheat flour sensitization. Poor cross-reactivity with its peach homolog was found in some patients.

CLINICAL IMPLICATIONS

LTPs can be considered relevant inhalant allergens linked to respiratory disorders. LTP from wheat (Tri a 14) can be used as a helpful tool for the diagnosis of baker's asthma.

Wheat IgE-mediated food allergy in European patients: alpha-amylase inhibitors, lipid transfer proteins and low-molecular-weight glutenins. Allergenic molecules recognized by double-blind, placebo-controlled food challenge

BACKGROUND

Three main problems hamper the identification of wheat food allergens: (1) lack of a standardized procedure for extracting all of the wheat protein fractions; (2) absence of double-blind, placebo-controlled food challenge studies that compare the allergenic profile of Osborne's three protein fractions in subjects with real wheat allergy, and (3) lack of data on the differences in IgE-binding capacity between raw and cooked wheat.

METHODS

Sera of 16 wheat-challenge-positive patients and 6 patients with wheat anaphylaxis, recruited from Italy, Denmark and Switzerland, were used for sodium dodecyl sulfate-polyacrylamide gel electrophoresis/immunoblotting of the three Osborne's protein fractions (albumin/globulin, gliadins and glutenins) of raw and cooked wheat. Thermal sensitivity of wheat lipid transfer protein (LTP) was investigated by spectroscopic approaches. IgE cross-reactivity between wheat and grass pollen was studied by blot inhibition.

RESULTS

The most important wheat allergens were the alpha-amylase/trypsin inhibitor subunits, which were present in all three protein fractions of raw and cooked wheat. Other important allergens were a 9-kDa LTP in the albumin/globulin fraction and several low-molecular-weight (LMW) glutenin subunits in the gluten fraction. All these allergens showed heat resistance and lack of cross-reactivity to grass pollen allergens. LTP was a major allergen only in Italian patients.

CONCLUSIONS

The alpha-amylase inhibitor was confirmed to be the most important wheat allergen in food allergy and to play a role in wheat-dependent exercise-induced anaphylaxis, too. Other important allergens were LTP and the LMW glutenin subunits.

The Triticum aestivum non-specific lipid transfer protein (TaLtp) gene family: comparative promoter activity of six TaLtp genes in transgenic rice

Plant non-specific lipid transfer proteins (nsLTPs) are encoded by a multigene family and support physiological functions, which remain unclear. We adapted an efficient ligation-mediated polymerase chain reaction (LM-PCR) procedure that enabled isolation of 22 novel Triticum aestivum nsLtp (TaLtp) genes encoding types 1 and 2 nsLTPs. A phylogenetic tree clustered the wheat nsLTPs into ten subfamilies comprising 1-7 members. We also studied the activity of four type 1 and two type 2 TaLtp gene promoters in transgenic rice using the 1-Glucuronidase reporter gene. The activities of the six promoters displayed both overlapping and distinct features in rice. In vegetative organs, these promoters were active in leaves and root vascular tissues while no beta-Glucuronidase (GUS) activity was detected in stems. In flowers, the GUS activity driven by the TaLtp7.2a, TaLtp9.1a, TaLtp9.2d, and TaLtp9.3e gene promoters was associated with vascular tissues in glumes and in the extremities of anther filaments whereas only the TaLtp9.4a gene promoter was active in anther epidermal cells. In developing grains, GUS activity and GUS immunolocalization data evidenced complex patterns of activity of the TaLtp7.1a, TaLtp9.2d, and TaLtp9.4a gene promoters in embryo scutellum and in the grain epicarp cell layer. In contrast, GUS activity driven by TaLtp7.2a, TaLtp9.1a, and TaLtp9.3e promoters was restricted to the vascular bundle of the embryo scutellum. This diversity of TaLtp gene promoter activity supports the hypothesis that the encoded TaLTPs possess distinct functions in planta.

Plant non-specific lipid transfer proteins: an interface between plant defence and human allergy

Plant non-specific LTPs (lipid transfer proteins) form a protein family of basic polypeptides of 9 kDa ubiquitously distributed throughout the plant kingdom. The members of this family are located extracellularly, usually associated with plant cell walls, and possess a broad lipid-binding specificity closely related to their three-dimensional structure. The nsLTP fold is characterized by a compact domain composed of 4 alpha-helices, firmly held by a network of 4 conserved disulphide bridges. This fold presents a large internal tunnel-like cavity, which can accommodate different types of lipids. nsLTPs are involved in plant defence mechanisms against phytopathogenic bacteria and fungi, and, possibly, in the assembly of hydrophobic protective layers of surface polymers, such as cutin. In addition, several members of the nsLTP family have been identified as relevant allergens in plant foods and pollens. Their high resistance to both heat treatment and digestive proteolytic attack has been related with the induction by these allergens of severe symptoms in many patients. Therefore, they are probably primary sensitizers by the oral route. nsLTP sensitization shows an unexpected pattern throughout Europe, with a high prevalence in the Mediterranean area, but a low incidence in Northern and Central European countries.

SAGE of the developing wheat caryopsis

Understanding the development of the cereal caryopsis holds the future for metabolic engineering in the interests of enhancing global food production. We have developed a Serial Analysis of Gene Expression (SAGE) data platform to investigate the developing wheat (Triticum aestivum) caryopsis. LongSAGE libraries have been constructed at five time-points post-anthesis to coincide with key processes in caryopsis development. More than 90,000 LongSAGE tags have been sequenced generating 29,261 unique tag sequences across all five libraries. Tag abundance, generated from cumulative tag counts, provides insight into the redundancy and diversity of each library. Annotation of the 500 most abundant tags spanning development highlights the array of functional groups being expressed. The relative frequency of these more abundant transcripts allows quantitative analysis of patterns of expression during grain development. We have identified activities of cellular proliferation/differentiation, the accumulation of storage proteins and starch biosynthesis. The abundance of calcium-dependent protein kinases indicate their importance in signalling across development. Acquisition of a broad array of defence coincides with storage accumulation and is dominated by inhibitors of amylase activity. Differential expression profiles of abundant tags from each library reveal the coordinated expression of genes responsible for the cellular events constituting caryopsis development. This SAGE platform has also provided a resource of novel sequence and expression information including the identification of potentially useful promoter activities. Further investigations into both the abundant and low expressing transcripts will provide greater insight into wheat caryopsis development and assist in wheat improvement programmes.