Glycine max (L.) Merr. (Soybean) metabolome responses to potassium availability

Potassium (K⁺) has vital physiological and metabolic functions in plants and its availability can impact tolerance to biotic and abiotic stress conditions. Limited studies have investigated the effect of K⁺ fertilization on soybean metabolism. Using integrated omics, ionomics and metabolomics, we investigated the field-grown Glycine max (soybean) response, after four K⁺ soil fertilization rates. Soybean leaf and pod tissue (valves and immature seeds) extracts were analysed by ultra-performance liquid chromatography coupled to high-resolution mass spectrometry (UPLC-HRMS) and inductively coupled plasma optical emission spectroscopy (ICP-OES). Multivariate analyses (PCA-X&Y e O2PLS-DA) showed that 51 compounds of 19 metabolic pathways were regulated in response to K⁺ availability. Under very low potassium availability, soybean plants accumulated of Ca²⁺, Mg²⁺, Fe²⁺, Cu²⁺, and B in young and old leaves. Potassium fertilization upregulated carbohydrate, galactolipid, and flavonol glycoside biosynthesis in leaves and pod valves, while K⁺ deficient pod tissues showed increasing amino acids, oligosaccharides, benzoic acid derivatives, and isoflavones contents. Severely K⁺ deficient soils elicited isoflavones, coumestans, pterocarpans, and soyasaponins in trifoliate leaves, likely associated to oxidative and photodynamic stress status. Additionally, results demonstrate that L-asparagine content is higher in potassium deficient tissues, suggesting this compound as a biomarker of K⁺ deficiency in soybean plants. These results demonstrate that potassium soil fertilization did not linearly contribute to changes in specialised constitutive metabolites of soybean. Altogether, this work provides a reference for improving the understanding of soybean metabolism as dependent on K⁺ availability.

Nutritional quality of different potassium efficiency types of vegetable soybean as affected by potassium nutrition

Pot experiments were conducted in 2017, 2019, and 2020 to examine the effects of potassium nutrition on the nutritional components of vegetable soybeans with different K efficiency at immature and mature stages. Two vegetable soybean varieties with higher K efficiency and two varieties with lower K efficiency were studied in the low available K soil under the condition of no K and normal K fertilization. The results indicated that almost all nutritional components in vegetable soybean were affected by K, genotypes, inter-annual differences, and their interactions. In general, no K fertilization increased protein and amino acid concentrations but decreased oil, soluble sugar, sucrose, K, Mg, and Fe concentrations in immature and mature vegetable soybean. The sensitivity of nutritional components to K nutrition differed among varieties. For instance, K high-efficiency varieties generally exhibited higher protein and amino acid concentrations without K application. K high-efficiency vegetable soybeans are low-K tolerance varieties to isoflavones. The results of this study provide insights for high yield and quality vegetable soybean breeding against soil K deficiency.

Chemical composition and lipoxygenase activity of soybean (Glycine max L. Merrill.) genotypes, specific for human consumption, with different tegument colours

Abstract Recently, in Brazil, coloured-tegument soybean cultivars have been developed, such as those with brown and black teguments. Soybeans with black teguments have been widely used for decades due to their health benefits and their use in oriental folk medicine as a result of the presence of phytochemicals. They have been recognized as health-promoting functional food ingredients due to their antioxidant activity, and are also known to have anti-cancer, hypoglycaemic and anti-inflammatory effects and have been used in the treatment of various circulatory disorders. This study aimed to determine the proximate composition, fatty acid levels and lipoxygenase activity of soybean lineages with different tegument colours intended for human consumption. The lineage MGBR10-16601 which has a yellow tegument, presented the highest protein and lowest fat contents, with values of 37.6 g 100 g-1 and 18.3 g 100 g-1, respectively. The lineage MGBR10-16201, which also has a yellow tegument, was identified as free of lipoxygenase isoenzymes. The unsaturated fatty acid levels ranged from 18.48 to 31.37 mg g-1 and from 47.36 to 58.31 mg g-1 for oleic and linoleic acids, respectively. The lineage BRN07-50543, which has a black tegument, presented high total isoflavone levels (546 mg 100 g-1), with an oleic acid level above and linoleic acid level below the standards established by the Codex Alimentarius for soybean oil, with values of 31.37 mg g-1 and 47.36 mg g-1, respectively. The cultivar BRSMG 790A, which has a yellow tegument, presented the lowest isoflavone level (171.4 mg 100 g-1). All the genetic materials examined presented crude protein, fat, dietary fibre and ash levels within the commercial parameters established for soybeans.

Proteomic analysis of anti-nutritional factors (ANF's) in soybean seeds as affected by environmental and genetic factors

The genotype (G), environment (E), and the relationship between G and E on soybean seed anti-nutritional factors (ANF's) were examined under three different agro-climatic conditions. The field trials were conducted at Maryland, South Carolina and South Dakota using nine region specific genotypes. At each location, the nine genotypes were grown with two planting/sowing dates. Differentially expressed protein spots from the two-dimensional gel electrophoresis were analyzed using mass spectrometry. Seven ANF's corresponding to soybean agglutinin and Kunitz trypsin inhibitor were identified based on the statistical significance levels at p<0.005. The G and E conditions (planting/sowing season) influences the ANF's content. This initial study suggests that early sowing reduces the total ANF's content irrespective of genotypes and their growing locations.

Characterization of Soybean Storage and Allergen Proteins Affected by Environmental and Genetic Factors

There is limited information on the influence of genetic and environmental variability on soybean protein composition. This study aimed to determine the role of genotype (G), environments (E), and the interrelationship of genotype and environment (G×E) on soybean seed protein. Three sets of nine soybean genotypes were grown in replicated trials at Maryland, South Carolina, and South Dakota. At each location, the nine genotypes were grown with two planting/sowing dates. We applied two-dimensional gel electrophoresis and mass spectrometry to study the variability of soybean storage and allergen proteins. Statistical analysis of 47 storage and 8 allergen proteins, in terms of differentially expressed protein spots significant at the p<0.005 level, was performed. We found more spots that showed statistically significant differences in expression among E compared to G and G×E interaction.