Mapping of Genomic Regions for Biochemical and Physiological Parameters Contributing Towards Drought Tolerance in Horsegram (Macrotyloma uniflorum (Lam.) Verdc.)

Horsegram (Macrotyloma uniflorum (Lam.) Verdc.) is a drought hardy legume which can be grown in varied soil and temperature regimes. Though it has numerous, nutritive and medicinal benefits, it still lags behind other legumes in terms of genomic resources and genetic improvement. This crop is mostly cultivated on marginal and drought-prone area; thus, genetics of drought stress tolerance can be understood by studying the various drought parameters. To get insight, quantitative trait loci for drought-tolerant traits were identified using an intraspecific mapping population of 162 F8 recombinant inbred lines derived from a cross between HPKM249 and HPK4. The linkage map already developed was used along with the phenotypic data for biochemical and physiological parameters to identify genomic regions which are linked to drought tolerance. In the study, a total of seven QTLs were identified for ten different drought-related traits. One QTL for malondialdehyde content on linkage group 2, two QTLs for root length on linkage groups 3 and 9, one QTL each for proline and chlorophyll content under drought stress on linkage group 4, and one QTL each for root dry weight and root fresh weight on linkage group 5 were identified using composite interval mapping. The identified QTLs will be utilized in marker-assisted breeding and increase our understanding on the physiology of drought stress tolerance.

Nuclear magnetic resonance-based chemical signature and nutritional discrimination of Macrotyloma uniflorum accessions from the alpine Himalayas

BACKGROUND

Macrotyloma uniflorum (horsegram) is cultivated in the alpine Himalayas for its nutritional benefits. The chemical diversity of M. uniflorum has been explored by several research groups, but none has reported the chemical signature to monitor the identity and quality. To overcome quality control problems and provide more accurate chemotype information, proton nuclear magnetic resonance (¹ H-NMR)-based chemical signature and tentative metabotype discrimination was studied.

RESULTS

Metabolites were identified by characteristic chemical shifts and their correlations in one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) experiments. The identifications were confirmed by reference standards, with in-house databases, and with public databases. From the analysis of seed samples from eight locations, NMR detected 46 diversified metabolites, including 18 amino acids, nine carbohydrates, three vitamins, seven flavonoids, and nine miscellaneous molecules (fatty acids/choline/phenolics/organic acids/sterols). These metabolites generated a single snapshot chemical signature for M. uniflorum. Greater content of identified metabolites was found at high elevations of 1829 m (55.78 g kg^-1 ) followed by 1000-1150 m (19.30-17.23 g kg^-1 ) and 1150-1450 m (7.33-13.41 g kg^-1 ). Principal component analysis of samples revealed that chemotypes grouped into three distinct clusters. 'Cluster-3' was positively correlated with metabolites and found the best nutritionally enriched chemotype.

CONCLUSIONS

A proton nuclear magnetic resonance-based M. uniflorum chemical signature was generated for the first time. The environmental conditions of 1829 m were most suitable for obtaining nutritionally enriched M. uniflorum crops. Overall, this information could help in the conservation, quality control, product development, and agriculture inventions of M. uniflorum. © 2021 Society of Chemical Industry.

Identification of QTLs Linked to Phenological and Morphological Traits in RILs Population of Horsegram (Macrotyloma uniflorum)

Horsegram [Macrotyloma uniflorum (Lam.) Verdc.] is an important legume but understudied in terms of its genetic improvement. Genetic information on various phenological and morphological traits may help in the utilization of new genes for breeding in horsegram and thus affect agronomic practices and crop yield. A total of 162 recombinant inbred lines derived from intraspecific crosses between HPKM249 × HPK4 was used to construct a genetic linkage map and to identify quantitative trait loci (QTLs) associated with phenological and morphological traits. Of the total 2011 molecular markers, which were screened on parental lines for polymorphism survey, 493 markers were found to be polymorphic and used for genotyping of recombinant inbred line population. Out of 493 polymorphic markers, 295 were mapped on ten linkage groups at LOD 3.5 spanning a total distance of 1,541.7 cM with an average distance between markers of 5.20 cM. Phenotypic data of two years at two different locations were used to identify QTLs by composite interval mapping A total of four QTLs (LOD ≥2.5) for phenological traits (days to 50% flowering, reproductive period and days to maturity) and seven QTLs (LOD ≥2.5) for morphological traits (plant height, primary branches and secondary branches) were detected across different environments. The phenotypic variation explained by QTLs ranged from 6.36 to 47.53%. The present study will help to augment scanty genomic information in this orphan crop that would provide genomics tools to breeders for its genetic enhancement through molecular-assisted selection.

Identification and validation of reference genes for qRT-PCR based studies in horse gram (Macrotyloma uniflorum)

The quantitative real-time polymerase chain reaction (qRT-PCR) is the most sensitive and commonly used technique for gene expression studies in biological systems. However, the reliability of qRT-PCR results depends on the selection of reference gene(s) for data normalization. Horse gram (Macrotyloma uniflorum) is an important legume crop on which several molecular studies have been reported. However, the stability of reference genes has not been evaluated. In the present study, nine candidate reference genes were identified from horse gram RNA-seq data and evaluated in two horse gram genotypes, HPK4 and HPKM317 under six abiotic stresses viz. cold, drought, salinity, heat, abscisic acid and methyl viologen-induced oxidative stress. The results were evaluated using geNorm, Bestkeeper, Normfinder and delta-delta Ct methods and comprehensive ranking was assigned using RefFinder and RankAggreg software. The overall result showed that TCTP was one of the most stable genes in all samples and in genotype HPK4, while in HPKM317 profilin was most stably expressed. However, PSMA5 was identified as least stable in all the experimental conditions. Expression of target genes dehydrin and early response to dehydration 6 under drought stress was also validated using TCTP and profilin for data normalization, either alone or in combination, which confirmed their suitability for qRT-PCR data normalization. Thus, TCTP and profilin genes may be used for qRT-PCR data normalization for molecular and genomic studies in horse gram.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12298-021-01104-0.

Influence of cooking methods on antinutritional factors, oligosaccharides and protein quality of underutilized legume Macrotyloma uniflorum

Macrotyloma uniflorum is a salubrious but underutilized legume mainly consumed in semi-arid zones of Africa, Australia and India. Various antinutritional factors- phytates, oxalates and oligosaccharides- has limited its consumption. Current work describes the influence of various thermal processing technologies - autoclaving, microwave, micronization and extrusion- on antinutritional profile, phenolic acid profile and protein digestibility of two selected varieties. Significant (p ≤ 0.05) reduction in antinutritional content was observed for horse gram grains processed using various thermal technologies. Among all processing technologies extrusion caused marked degradation in antinutritional components. The reduction in oxalic acid, trypsin inhibitor, phytates and tannins ranged from 33 to 87 %, 77-82%, 33-60% and 51-66% respectively. Further, the decline in content of various oligosaccharides viz. raffinose, stachyose and verbascose varied from 36 to 61 %, 25-49% and 30-74% respectively for both the varieties. Although extrusion caused significant (p ≤ 0.05) decrease in the essential amino acid index and protein efficiency ratio, simultaneous increased was observed in biological value. The processing had significant (p ≤ 0.05) impact on grain antinutritional content and also retained its substantial functional properties. This establishes the utility of grain and promote the introduction of these new grains and enlarge the market of novel healthy foods.

Assessment of calcium oxalate crystal inhibition potential, antioxidant activity and amino acid profiling in horse gram (Macrotyloma uniflorum): high altitude farmer's varieties

Seeds of Macrotyloma uniflorum collected from different Himalayan regions of Himachal Pradesh, India were screened for inhibition potential of calcium oxalate crystals along with their antioxidant and amino acid profiling. Aqueous, ethanol, 50% ethanol extracts were tested using agar-gel overlay, nucleation, and artificial urine methods in comparison to marketed products. The aqueous extract of Sundernagar and Rampur seeds showed highest inhibition potential (9.0 ± 0.81 mm) than alcohol and hydroalcohol. Sundernagar seeds (aqueous extract) also showed maximum inhibition (45 ± 1.2 and 24 ± 0.88%) in nucleation and artificial urine assay, respectively. The Tris-buffer (pH. 8.0) extract of dry seeds showed more inhibition with low protein than high protein germinated seeds. The findings revealed that horse gram protein is not alone responsible for CaOx-crystals inhibition but its secondary metabolites may also contribute. Among all samples, buffer and aqueous extracts showed maximum activity, followed by hydroalcohol and alcohol. Further, TLC and UPLC method were used to monitor the presence of amino acids in aqueous and Cystone extracts. Sundernagar seeds contain 11 amino acids with additional arginine, aspargine, and methionine. Moreover, higher antioxidant potential was observed in seeds of high altitude, which relates the factors of altitudinal variation in secondary metabolism of plants. Therefore, this study will help in the development of economical and more reliable plant based nutraceuticals for kidney stone problems and related health issues.

Effect of Macrotyloma uniflorum in ethylene glycol induced urolithiasis in rats

Macrotyloma uniflorum Linn. (Fabaceae) seeds are widely used for their diuretic and urolithiatic effects in India. The present study investigated the effect of aqueous extract of Macrotyloma uniflorum seeds (AEMU) on ethylene glycol induced urolithiasis in rats. To induce urolithiasis, 0.75% v/v ethylene glycol was administered orally for 14 days. The curative doses of 400 and 800 mg/kg were administered from 15^th to 28^th day. On the 28th day, 24 h urine, serum was collected and various biochemical parameters were estimated in urine, serum and kidney homogenate along with histology of kidney. Co-administration of AEMU with ethylene glycol has significantly (p < 0.001) increased the urine volume and the level of calculus inhibitors like magnesium, citrate and decreased the level of calculus promoters like calcium, oxalate, uric acid and urea also decreased in crystalluria in urine. AEMU supplement also prevented the pathological changes in the kidney and increased the glomerulus activity of the kidney. These results indicate that AEMU showed significant activity in urolithiasis which might be due to its diuretic, calcium oxalate crystal formation inhibitory effects and its ability to increase the levels of inhibitors and decrease the level of promoters of urolithiasis.

Nutrient mixture from germinated legumes: Enhanced medicinal value with herbs-attenuated liver cirrhosis

Among various food processing strategies, germination and dehulling enhance the nutritional content of the food, and the addition of herbs to this could improve the medicinal value. The milled powders of germinated Macrotyloma uniflorum (horse gram) and Vigna radiata (green gram) were used to make the nutrient mixture. Further, Curcuma longa (turmeric) and Trigonella foenum graecum (fenugreek) were used to improve its medicinal value. The prepared nutrient mixture has high nutritional value, antioxidant potential, and reduced antinutrient factors. Supplementation of nutrient mixture reduced oxidative stress-mediated hepatocyte injury on the CCl₄ -induced liver cirrhosis model. Further, histological examination (H&E and Sirius red), matrix metalloproteinase gelatin zymography, and Western blot revealed the management of hepatic stellate cells in an inactive stage thereby reduced cirrhosis. These findings conclude that the supplementation of nutrient mixture formulation protected and effectively prevented liver cirrhosis. PRACTICAL APPLICATIONS: This study has a good impact on nutritional therapy for liver diseases. Many of the chronic liver diseases are associated with severe malnutrition and hypoalbuminemia, which further worsens the condition. This study would emphasize the nutritional therapy to treat such imbalance and enriching the medicinal value of nutrition mixture with herbs could target different pathophysiological changes and provide better defense in liver disease patients. Since this nutrient mixture is from common edible natural resources, it could reach the pharmaceutical industry's attention to the highest production and marketing.

Diversity in protein secondary structure, molecular weight, mineral and amino acid composition of lentil and horse gram germplasm

Lentil and horse gram germplasm was assessed for variety in seed and flour properties. Horsegram grains showed higher a* and b* and lower L* values as compared to lentil grains indicating lentil grains were lighter in color as compared to horse gram. Both the pulses showed significant differential accumulation of minerals. Flours from horse gram lines showed higher Mn, K, Mg, Na, Zn and Ca content and lower Cu and Fe content as compared to lentil lines. Polypeptide of 42 kDa was present in IC94636 and IC139555 only and 35 kDa PP subunit was absent in all the horse gram lines except IC94636. Major polymorphism among lentil lines was observed in 10, 35-37 and 55-49 kDa PP subunits. Amount of β-sheets and β-turns was the highest whereas that of antiparallel β-sheets was the lowest. NIC17550, NIC17551 and NIC17552 showed higher content of antiparallel β-sheets and random coils among lentil lines. PL1 showed the highest portion of α-helixes and β-turns whereas PL57 showed the highest proportion of β-sheets among lentil lines. Lentil flours showed higher proportion of aspartic acid, glutamic acid, asparagine, serine, citrulline and serine and lower proportion of histidine, threonine, GABA, tyrosine and cystine as compared to horse gram.

Purification and characterization of acid phosphatase from Macrotyloma uiflorum seeds

Acid phosphatases play a crucial role in food processing industries to reduce phosphate content of food. Here in acid phosphatase from the seeds of Macrotyloma uniflorum has been purified to homogeneity using UNOsphere-S cation exchange chromatography followed by gel filtration with 81.85 fold purification. Molecular weight of purified enzyme was 55,000 (± 1040) Daltons under physiological conditions. It was a heterodimer of subunits having molecular weights 27,093 and 28,241 Daltons as determined by MALDI-TOF analysis. The optimum pH and temperature for the purified enzyme was 5.0 and 50 °C respectively. The enzyme was stable in the pH range 3.5-5.5 and showed temperature stability up to 60 °C. Substrate specificity of enzyme was checked with different substrates namely, p-nitrophenyl phosphate (p-NPP), ATP, ADP, glucose 6-phosphate, glucose-1-phosphate, fructose 6-phosphate, phenyl phosphate, α-naphthyl-phosphate, pyridoxyl phosphate and β-glycerophosphate. Enzyme showed high substrate specificity towards p-NPP, phenyl phosphate, ATP and α-naphthyl phosphate. K_m and V_max of enzyme were found to be 0.934 mM and 1.333 mM/min respectively with respect to p-NPP as a substrate. Chemical modification studies showed that tryptophan was present at the active site of the enzyme.

Chemical composition of ethanol extract of Macrotyloma uniflorum (Lam.) Verdc. using GC-MS spectroscopy

BACKGROUND

Macrotyloma uniflorum Linn (Fabaceae) is a herbaceous plant with annual branches. It is used in kidney stones, inflamed joints, fever, musculoskeletal disorders, sinus wounds and localized abdominal tumors. It is reported as an antioxidant and nutraceutical (forage and food). GC-MS analysis of ethanol extract has led to identification of twenty-eight compounds from M. uniflorum by comparison of their retention indices and mass spectra fragmentation patterns with those stored on the GC-MS computer library.

RESULTS

The main constituents identified were mome inositol, ethyl alpha-d-glucopyranoside, n- hexadecanoic acid, linoleic acid (9, 12-octadecadienoic acid), its esters and ethyl derivatives, Vitamin E, stigmasterol and 3-beta-stigmast-5-en-3-ol.

CONCLUSIONS

The extracts are rich in linoleic acid and its esters, mome inositol and ethyl alpha-d-glucopyranoside; therefore, this plant can be medicinally beneficial as an antioxidant, in diabetes and its related disorders.

The effect of Macrotyloma uniflorum seed on bile lithogenicity against diet induced cholelithiasis on mice

Background:

The seeds of Macrotyloma uniflorum Lam. (Family Fabaceae) contain extractable total and tannins with reported hepatoprotective, hypocholesterolemic and antioxidant activity. In this study, dietary M. uniflorum seed, methanolic and acetone extracts (ME and AE) were examined for their bile-antilithogenic potential.

Materials and Methods:

Mice fed with 1% cholesterol and 0.5% cholic acid lithogenic (LG) diet for 8 weeks resulted in cholesterol super saturation in gallbladder bile, which promotes the formation of cholesterol gallstones (CGSs).

Results:

AE reduced the CGS incidence by 60.21%, and serum total cholesterol, triglyceride (TG), very low density lipoprotein (LDL) and LDL compared to control animals. Seed extracts at 300 mg/kg dose markedly reduced biliary cholesterol (BC) and decreased bile salt content. The ratio of BC to phospholipid which was 2.64 in the LG diet group was reduced to 1.57–1.35 in the M. uniflorum seed extracts treated groups. Liver cholesterol and TG were decreased significantly by feeding of ME and AE at 300 mg/kg dose. AE significantly reversed the changes in apolipoproteins A-I and C-II level disturbed by LG diet.

Conclusions:

M. uniflorum seed exerted antilithogenic influence by decreasing the cholesterol hyper-secretion into bile and increasing the bile acid output, thus decreasing the formation of LG bile in mice. The effect was maximum in the AE as it also reduced papillary proliferation of gallbladder and fatty degeneration of the liver. The potential antilithogenic effect of the AE of M. uniflorum may be due to antioxidant property of its rich total polyphenol and tannins content.