Identification of genes associated to β -N oxalyl- L-α, β-diaminopropionic acid and their role in mitigating salt stress in a low-neurotoxin cultivar of Lathyrus sativus

Grass pea has the potential to become a miracle crop if the stigma attached to it as a toxic plant is ignored. In light of the following, we conducted transcriptome analyses on the high and low ODAP-containing cultivars i.e., Nirmal and Bidhan respectively in both normal and salt stress conditions. In this study, genes that work upstream and downstream to β-ODAP have been found. Among these genes, AAO3 and ACL5 were related to ABA and polyamine biosynthesis, showing the relevance of ABA and polyamines in boosting the β-ODAP content in Nirmal. Elevated β-ODAP levels in salt stress-treated Bidhan may have evolved tolerance by positively regulating the expression of genes involved in phenylpropanoid and jasmonic acid biosynthesis. Although the concentration of β-ODAP in Bidhan increased under salt stress, it was lower than in stress-treated Nirmal. Despite this, the expression of stress-related genes that work downstream to β-ODAP was found higher in stress-treated Bidhan. This could be because stress-treated Nirmal has lower GSH, proline, and higher H2O2, resulting in the development of severe oxidative stress. Overall, our research not only identified new genes linked with β-ODAP, but also revealed the molecular mechanism by which a low β-ODAP-containing cultivar developed tolerance against salinity stress.

The Comparative Effect of Lactic Acid Fermentation and Germination on the Levels of Neurotoxin, Anti-Nutrients, and Nutritional Attributes of Sweet Blue Pea (Lathyrus sativus L.)

Grass pea (Lathyrus sativus L.), an indigenous legume of the subcontinental region, is a promising source of protein and other nutrients of health significance. Contrarily, a high amount of β-N-oxalyl-l-α,β-diaminopropionic acid (β-ODAP) and other anti-nutrients limits its wider acceptability as healthier substitute to protein of animal and plant origin. This study was aimed at investigating the effect of different processing techniques, viz. soaking, boiling, germination, and fermentation, to improve the nutrient-delivering potential of grass pea lentil and to mitigate its anti-nutrient and toxicant burden. The results presented the significant (p < 0.05) effect of germination on increasing the protein and fiber content of L. sativus from 22.6 to 30.7% and 15.1 to 19.4%, respectively. Likewise, germination reduced the total carbohydrate content of the grass pea from 59.1 to 46%. The highest rate of reduction in phytic acid (91%) and β-ODAP (37%) were observed in germinated grass pea powder, whereas fermentation anticipated an 89% reduction in tannin content. The lactic acid fermentation of grass pea increased the concentration of calcium, iron, and zinc from 4020 to 5100 mg/100 g, 3.97 to 4.35 mg/100 g, and 3.52 to 4.97 mg/100 g, respectively. The results suggest that fermentation and germination significantly (p < 0.05) improve the concentration of essential amino acids including threonine, leucine, histidine, tryptophan, and lysine in L. sativus powder. This study proposes lactic acid fermentation and germination as safer techniques to improve the nutrient-delivering potential of L. sativus and suggests processed powders of the legume as a cost-effective alternative to existing plant proteins.

Diamine Oxidase as a Therapeutic Enzyme: Study of Germination from Vegetal Sources and Investigation of the Presence of β-N-Oxalyl-L-α,β-diaminopropionic Acid (β-ODAP) Using LC-MS/MS

Vegetal diamine oxidase (vDAO), an enzyme proposed to relieve symptoms of histaminosis, shows better reactivity with histamine and aliphatic diamines, as well as higher enzymatic activity than DAO of animal origin. The objective of this study was to evaluate the enzyme activity of vDAO from germinating grains from Lathyrus sativus (grass pea) and Pisum sativum (pea), and to verify the presence of a neurotoxin, β-N-Oxalyl-L-α,β-diaminopropionic acid (β-ODAP), in the crude extract obtained from their seedlings. A targeted liquid chromatography-multiple-reaction monitoring mass spectrometry method was developed and used to quantify β-ODAP in the analysed extracts. An optimized sample preparation procedure, involving protein precipitation with acetonitrile followed by mixed-anion exchange solid-phase extraction, allowed for high sensitivity and good peak shape for β-ODAP detection. The Lathyrus sativus extract exhibited the highest vDAO enzyme activity of the extracts, followed by the extract from pea cultivar Amarillo from the Crop Development Centre (CDC). The results have also shown that even though β-ODAP was present in the crude extract from L. sativus, its content was far below the toxicity threshold (300 mg of β-ODAP/kg body/day). CDC Amarillo showed 5000-fold less β-ODAP than the undialysed L. sativus extract. It was concluded that both species can be considered as convenient sources of vDAO for potential therapeutic use.

Effects of phytase-supplemented fermentation and household processing on the nutritional quality of Lathyrus sativus L. seeds

Grass pea (Lathyrus sativus L.) is commonly consumed in cooked, fermented, and roasted forms in Ethiopia. However, the impacts of household processing practices on its nutrients, antinutrients, and toxic compounds have not been adequately studied. Therefore, the effects of household processing and fermentation in the presence and absence of a phytase on the contents of β-N-oxalyl-L-α,β-diaminopropionic acid (β-ODAP), myo-inositol phosphates, crude protein, minerals and the in vitro bioaccessibility were investigated. Fermentation exhibited a significant decline in β-ODAP (13.0-62.0%) and phytate (7.3-90.5%) irrespective of the presence of phytase. Pressure and pan cooking after discarding the soaking water resulted in a 27.0 and 16.2% reduction in β-ODAP. A 30% reduction in phytate was observed during germination followed by roasting. In addition, germination resulted in a significant (p < 0.05) increase in crude protein. Germination and germination followed by roasting resulted in the highest Fe bioaccessibilities (more than 25 fold higher compared to untreated samples) followed by pressure cooking and soaking. Processing also improved Zn bioaccessibilities by 50.0% (soaked seed without soaking water), 22.5% (soaked seed with soaking water), and 4.3% (germination). Thus, the processing technologies applied were capable of reducing the content of phytate (InsP6) and β-ODAP with a concomitant increase in mineral bioaccessibilities. Processing of grass peas could therefore contribute to their more widespread utilization.

Neurolathyrism in goat (Capra hircus) kid: Model development

The present study was undertaken to develop an animal model to study neurolathyrism. For this purpose 24 goat (Capra hircus) kids (new born, 15 days old) were divided into four groups. Group I Control, Group II Low toxin (0.17 g% β-ODAP containing grass pea), Group III high toxin (0.96 g% β-ODAP containing grass pea) and Group IV high toxin (0.96 g% β-ODAP containing grass pea flour (powder) fortified with 5 mg% pure β-ODAP). The experiment was continued for 3 months. Clinical examination was carried out weekly. Muscle conduction velocity (MCV), nerve conduction velocity (NCV), blood and urinary β-ODAP, nitrite in blood and cerebrospinal fluid (CSF) examination were performed by standard methods. Clinical examination showed neurolathyrism symptoms in three kids. The abnormal MCV and NCV were observed in all the experimental animals. Blood nitrite, blood and urine β-ODAP levels were significantly increased in experimental groups. Three kids were affected with neurolathyrism due to consumption of grass pea irrespective of its β-ODAP content and kid may serve as a neurolathyrism model.

Proteomic Comparison of Three Extraction Methods Reveals the Abundance of Protease Inhibitors in the Seeds of Grass Pea, a Unique Orphan Legume

Grass pea is an orphan legume that is grown in many places in the world. It is a high-protein, drought-tolerant legume that is capable of surviving extreme environmental challenges and can be a sole food source during famine. However, grass pea produces the neurotoxin β-N-oxalyl-L-α,β-diaminopropionic acid (β-ODAP), which can cause a neurological disease. This crop is promising as a food source for both animals and humans if β-ODAP levels and other antinutritional factors such as protease inhibitors are lowered or removed. To understand more about these proteins, a proteomic analysis of grass pea was conducted using three different extraction methods to determine which was more efficient at isolating antinutritional factors. Seed proteins extracted with Tris-buffered saline (TBS), 30% ethanol, and 50% isopropanol were identified by mass spectrometry, resulting in the documentation of the most abundant proteins for each extraction method. Mass spectrometry spectral data and BLAST2GO analysis led to the identification of 1376 proteins from all extraction methods. The molecular function of the extracted proteins revealed distinctly different protein functional profiles. The majority of the TBS-extracted proteins were annotated with nutrient reservoir activity, while the isopropanol extraction yielded the highest percentage of endopeptidase proteinase inhibitors. Our results demonstrate that the 50% isopropanol extraction method was the most efficient at isolating antinutritional factors including protease inhibitors.

An Improved HILIC HPLC-MS/MS Method for the Determination of β-ODAP and Its α Isomer in Lathyrus sativus

β-N-Oxalyl-l-α,β-diaminopropionic acid (β-ODAP) is a non-protein amino acid present in Lathyrus sativus (grass pea) and other Lathyrus species, in parallel with its nontoxic isomer, α-ODAP. When consuming grass pea for several months as staple food, β-ODAP may cause neurolathyrism, a motor neuron degeneration syndrome. Therefore, the independent quantification of both ODAP isomers instead of only the total amount in grass pea allows the identification of less toxic varieties and the development of tools to support breeding for improving grass pea quality. In this work, a simple and fast HPLC-MS/MS method was developed without sample derivatization, using a hydrophilic interaction chromatography (HILIC) column and an isocratic gradient of eluents for 18 min, which allowed the determination of both α- and β-ODAP. The proposed method was fully validated and applied to the determination of α- and β-ODAP contents in a diverse collection of 107 grass pea accessions representative of the main grass pea-growing geographical regions in the world, with the prompt identification of contrasting accessions. β-ODAP content in the analyzed grass pea samples ranged from 0.45 ± 0.02 to 6.04 ± 0.45 mg g⁻¹. The moderate correlation found between α- and β-ODAP contents (0.65) in this collection reinforces the importance of the independent quantification of both ODAP isomers.

Reduction of β-ODAP and IP6 contents in Lathyrus sativus L. seed by high hydrostatic pressure

Grass pea (Lathyrus sativus L.) seeds contain an endogenous neurotoxic non-proteinogenic amino acid, β-N-oxalyl-l-α,β-diaminopropionic acid (β-ODAP), a major limiting factor-for their human consumption. Furthermore, phytate (IP₆), a well-known antinutrient is present in concentration capable of hindering bioavailability of iron (Fe), zinc (Zn), calcium (Ca), phosphorus (P) and other micronutrients from the seeds. Due to the reported capability of high hydrostatic pressure (HHP) to reduce the content of certain antinutritional/toxic agents in seeds and grains, the impact of HHP on the reduction of β-ODAP and IP₆ were investigated. The contents of β-ODAP of accessions from different regions in Ethiopia were found to be in the range of 51.94 to 806.52 mg/100 g. Accession (GF₁- Alemu, AK) exhibiting the highest β-ODAP content was selected for HHP treatment in soaked and batter forms using Central Composite Face Centered Design of experiments. The best HHP conditions in respect to β-ODAP reduction were also applied to the accession (GP-240038) with the lowest β-ODAP-content, a genetically improved variety (Wassie) and a variety from Germany (GR). The HHP treatment at 600 MPa for 25 min of seeds soaked for 6 h and 12 h exhibited the maximum reduction of β-ODAP (232.11 mg/100 g) and IP₆ (21.11 mg/100 g) respectively. The combined incremental effect of pressure and soaking time resulted in a more significant (p ≤ .001) reduction in both compounds than the interaction of pressure with holding time (p ≤ .05). A reduction of β-ODAP from 36.00 to 71.22% by soaked-HHP treatment was observed. β-ODAP reductions were always higher for soaked compared to batter grass pea seeds. IP₆ contents after HHP treatment ranged from 33.65 mg/100 g to nill. It can be concluded that pressure, soaking and holding time as well as the grass pea seed accession/variety had great impact on molecular structure changes, enhancement of enzyme activity and reduction in β-ODAP and IP₆ content.

Tissue specific expression and in-silico characterization of a putative cysteine synthase gene from Lathyrus sativus L

Grass pea (Lathyrus sativus L.) is a worldwide popular pulse crop especially for its protein rich seeds with least production cost. However, the use of the crop became controversial due to the presence of non-protein amino acid, β-N-oxalyl-L-α, β-diaminopropionic acid (β-ODAP) in its seed and leaf, which is known as the principle neurotoxin to cause neurolathyrism (a motor neurodegenerative disease of humans and animals) during prolonged consumption as regular diet. Till date, the knowledge on β-ODAP biosynthesis in Lathyrus sp. is limited only to a small part of the complex bio-chemical steps involved including a few known sulfur-containing enzymes (viz. cysteine synthase, ODAP synthase etc.). In Lathyrus sativus, biosynthesis of β-ODAP varies differentially in a tissue-specific manner as well as in response to several environmental stresses viz. zinc deficiency, iron over-exposure, moisture stress etc. In the present study, a novel cysteine synthase gene (LsCSase) from Lathyrus sativus L was identified and characterized through bioinformatics approaches. The bioinformatic analysis revealed that LsCSase showed maximum similarity with the O-acetyl serine (thiol) lyase of Medicago truncatula with respect to several significant sequence-specific conserved motifs (cysK, CBS like, ADH_zinc_N, PALP), sub-cellular localization (chloroplast or cytoplasm) etc., similar to other members of cysteine synthase protein family. Moreover, the tissue-specific regulation of the LsCSase as well as its transcriptional activation under certain previously reported stressed conditions (low Zn⁺²-high Fe⁺², PEG induced osmotic stress) were also documented through quantitative real-time PCR analyses, suggesting a possible link between the LsCSase gene activation and β-ODAP biosynthesis to manage external stresses in grass pea. This preliminary study offers a probable way towards the development of less toxic consumer-safe grass pea by down-regulation or deactivation of such gene/s (cysteine synthase) through genetic manipulations.

Metabolomics Approach To Understand Mechanisms of β-N-Oxalyl-l-α,β-diaminopropionic Acid (β-ODAP) Biosynthesis in Grass Pea (Lathyrus sativus L.)

A study was performed to identify metabolic processes associated with β-ODAP synthesis in grass pea using a metabolomics approach. GC-MS metabolomics was performed on seedlings at 2, 6, and 25 days after sowing. A total of 141 metabolites were detected among the three time points representing much of grass pea primary metabolism, including amino acids, carbohydrates, purines, and others. Principal component analysis revealed unique metabolite profiles of grass pea tissues among the three time points. Fold change, hierarchical clustering, and orthogonal projections to latent structures-discriminant analyses, and biochemical pathway ontologies were used to characterize covariance of metabolites with β-ODAP content. The data indicates that alanine and nitrogen metabolism, cysteine and sulfur metabolism, and purine, pyrimidine, and pyridine metabolism were associated with β-ODAP metabolism. Our results reveal the metabolite profiles in grass pea development and provide insights into mechanisms of β-ODAP accumulation and degradation.

β-N-Oxalyl-l-α,β-diaminopropionic Acid (β-ODAP) Content in Lathyrus sativus: The Integration of Nitrogen and Sulfur Metabolism through β-Cyanoalanine Synthase

Grass pea (Lathyrus sativus L.) is an important legume crop grown mainly in South Asia and Sub-Saharan Africa. This underutilized legume can withstand harsh environmental conditions including drought and flooding. During drought-induced famines, this protein-rich legume serves as a food source for poor farmers when other crops fail under harsh environmental conditions; however, its use is limited because of the presence of an endogenous neurotoxic nonprotein amino acid β-N-oxalyl-l-α,β-diaminopropionic acid (β-ODAP). Long-term consumption of Lathyrus and β-ODAP is linked to lathyrism, which is a degenerative motor neuron syndrome. Pharmacological studies indicate that nutritional deficiencies in methionine and cysteine may aggravate the neurotoxicity of β-ODAP. The biosynthetic pathway leading to the production of β-ODAP is poorly understood, but is linked to sulfur metabolism. To date, only a limited number of studies have been conducted in grass pea on the sulfur assimilatory enzymes and how these enzymes regulate the biosynthesis of β-ODAP. Here, we review the current knowledge on the role of sulfur metabolism in grass pea and its contribution to β-ODAP biosynthesis. Unraveling the fundamental steps and regulation of β-ODAP biosynthesis in grass pea will be vital for the development of improved varieties of this underutilized legume.

Determination of β-N-oxalyl-L-α,β-diaminopropionic acid and homoarginine in Lathyrus sativus and Lathyrus cicera by capillary zone electrophoresis

BACKGROUND

Lathyrus species as legumes represent an alternative protein source for human and animal nutrition. Heavy consumption of these species can lead to lathyrism, caused by the non-protein amino acid β-N-oxalyl-l-α,β-diaminopropionic acid (β-ODAP). Currently, there is no well-defined level below which β-ODAP is considered non-toxic. In this work, the β-ODAP content was determined in L. sativus and L. cicera samples to assess their potential toxicity. Homoarginine is another non-protein amino acid found in Lathyrus spp. with interesting implications for human and animal nutrition.

RESULTS

The level of β-ODAP found in these two species ranged from 0.79 to 5.05 mg g(-1). The homoarginine content of the samples ranged from 7.49 to 12.44 mg g(-1).

CONCLUSION

This paper describes an accurate, fast and sensitive method of simultaneous detection and quantification of β-ODAP and homoarginine by capillary zone electrophoresis in L. cicera and L. sativus seeds. Moreover, several methods of extraction were compared to determine the highest performance.