Nitrogen regulates the synthesis of hydrophobic amino acids to improve protein structural and gel properties in common buckwheat.

Nitrogen (N) fertilizer impacts the grain quality of common buckwheat, but the effects and regulatory mechanisms of N on various protein parameters of buckwheat are not fully understood. The purpose of this study was to investigate the particle morphology, structural and gel properties, and regulation mechanism of buckwheat protein under four N levels. The bulk density, surface hydrophobicity, particle size, and thermal properties of the buckwheat protein were maximized through the optimal N application (180 kg N/ha), further enhancing the thermal stability of the protein. N application increased the ß-sheet content and reduced the random coil content. Appropriate N fertilizer input enhanced the tertiary structure stability and gel elasticity of buckwheat protein by promoting hydrophobic interactions, disulfide bonds, ionic bonds, storage modulus and loss modulus. The differentially expressed proteins induced by N are primarily enriched in small ribosomal subunit and ribosome, improving protein quality mainly by promoting the synthesis of hydrophobic amino acids. Future agriculture should pay attention to the hydrophobic amino acid content of buckwheat to effectively improve protein quality. This study further advances the application of buckwheat protein in the field of food processing and provides a theoretical basis for the extensive development and utilization of buckwheat protein.

Proteomics characterization of the synthesis and accumulation of starch and amino acid driven by high-nitrogen fertilizer in common buckwheat.

The accumulation of starches and amino acid content of common buckwheat is promoted by Nitrogen (N), but the molecular mechanism is not clear. N applications with 0 (control group) and 180 kg/ha were designed. High-N significantly improved grain fullness and increased the starch, amylopectin and amylose content. The number of upregulated differentially expressed proteins (DEPs) induced by N gradually increased with the filling progress. N resulted in 139, 341 and 472DEPs significant upregulation at 10d, 20d and 30d and they were mainly related to the 'Starch and sucrose metabolism', 'Protein processing in endoplasmic reticulum' and 'Ribosome' by kyoto encyclopedia of genes and genomes analysis. High-N induced one sucrose synthase, two alpha-amylases and six alpha-glucan phosphorylases significant upregulation at 30d and one alpha-amylases upregulation at 10d, and the expression levels of these proteins showed a significant linear relationship with starch and amylose contents. N promoted the arginine and lysine biosynthesis at the late filling stage. These results elucidated that the mechanism of N promoted common buckwheat starches and amino acid accumulation. The identified crucial proteins may improve buckwheat quality.

Genome-wide identification and expression analysis of the plant-specific PLATZ gene family in Tartary buckwheat (Fagopyrum tataricum).

BACKGROUND: Plant AT-rich sequence and zinc-binding (PLATZ) proteins belong to a novel class of plant-specific zinc-finger-dependent DNA-binding proteins that play essential roles in plant growth and development. Although the PLATZ gene family has been identified in several species, systematic identification and characterization of this gene family has not yet been carried out for Tartary buckwheat, which is an important medicinal and edible crop with high nutritional value. The recent completion of Tartary buckwheat genome sequencing has laid the foundation for this study. RESULTS: A total of 14 FtPLATZ proteins were identified in Tartary buckwheat and were classified into four phylogenetic groups. The gene structure and motif composition were similar within the same group, and evident distinctions among different groups were detected. Gene duplication, particularly segmental duplication, was the main driving force in the evolution of FtPLATZs. Synteny analysis revealed that Tartary buckwheat shares more orthologous PLATZ genes with dicotyledons, particularly soybean. In addition, the expression of FtPLATZs in different tissues and developmental stages of grains showed evident specificity and preference. FtPLATZ3 may be involved in the regulation of grain size, and FtPLATZ4 and FtPLATZ11 may participate in root development. Abundant and variable hormone-responsive cis-acting elements were distributed in the promoter regions of FtPLATZs, and almost all FtPLATZs were significantly regulated after exogenous hormone treatments, particularly methyl jasmonate treatment. Moreover, FtPLATZ6 was significantly upregulated under all exogenous hormone treatments, which may indicate that this gene plays a critical role in the hormone response of Tartary buckwheat. CONCLUSIONS: This study lays a foundation for further exploration of the function of FtPLATZ proteins and their roles in the growth and development of Tartary buckwheat and contributes to the genetic improvement of Tartary buckwheat.

Identifying the primary meteorological factors affecting the growth and development of Tartary buckwheat and a comprehensive landrace evaluation using a multi-environment phenotypic investigation.

BACKGROUND: Tartary buckwheat (Fagopyrum tataricum) is a traditional edible and medicinal crop and has been praised as one of the green foods for humans in the 21st century. However, its production and promotion are restricted by the low yields of current varieties. The interaction of genotype and environment could lead to inconsistent phenotypic performance of genotypes across different environments. Climate change has intensified these effects and poses a substantial threat to crop production. RESULTS: In the present study, the effects of meteorological factors on the phenotypic traits of 200 Tartary buckwheat landraces across four macro-environments were investigated. Overall, the phenotypic performance of these Tartary buckwheat landraces was markedly varied across the different environments. Also, the average daily temperature and precipitation had relatively higher impacts on phenotypic performance. The results also revealed the negative impacts of relative humidity on the yield-related traits. Twenty-five Tartary buckwheat landraces were ultimately identified as having good overall phenotypic performance and high yield stability. CONCLUSION: Understanding the impacts of meteorological factors on the phenotypic performance of crops can guide appropriate measures and facilitate germplasm selection for yield enhancement in the context of climate change. The landraces selected comprehensively in this study could be used as parents or intermediate materials for breeding high-quality Tartary buckwheat varieties in the future. The methods used could also be extended to other crops for breeding and germplasm innovation. © 2021 Society of Chemical Industry.

Exogenous Melatonin Modulates the Physiological and Biochemical Mechanisms of Drought Tolerance in Tartary Buckwheat (Fagopyrum tataricum (L.) Gaertn).

Tartary buckwheat is one of the nutritious minor cereals and is grown in high-cold mountainous areas of arid and semi-arid zones where drought is a common phenomenon, potentially reducing the growth and yield. Melatonin, which is an amphiphilic low molecular weight compound, has been proven to exert significant effects in plants, under abiotic stresses, but its role in the Tartary buckwheat under drought stress remains unexplored. We evaluated the influence of melatonin supplementation on plant morphology and different physiological activities, to enhance tolerance to posed drought stress by scavenging reactive oxygen species (ROS) and alleviating lipid peroxidation. Drought stress decreased the plant growth and biomass production compared to the control. Drought also decreased Chl a, b, and the Fv/Fm ratio by 54%, 70%, and 8%, respectively, which was associated with the disorganized stomatal properties. Under drought stress, H2O2, O2•-, and malondialdehyde (MDA) contents increased by 2.30, 2.43, and 2.22-folds, respectively, which caused oxidative stress. In contrast, proline and soluble sugar content were increased by 84% and 39%, respectively. However, exogenous melatonin (100 µM) could improve plant growth by preventing ROS-induced oxidative damage by increasing photosynthesis, enzymatic antioxidants (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase), secondary metabolites like phenylalanine ammonialyase, phenolics, and flavonoids, total antioxidant scavenging (free radical DPPH scavenging), and maintaining relative water content and osmoregulation substances under water stress. Therefore, our study suggested that exogenous melatonin could accelerate drought resistance by enhancing photosynthesis and antioxidant defense in Tartary buckwheat plants.

Isolation and characterization of starch from light yellow, orange, and purple sweet potatoes.

Sweet potato is attracting increased research attention because of its high nutritional value (e.g., carotene, anthocyanin, and minerals) and the wide application of its starch in foods and nonfoods. Herein, eight Chinese sweet potato varieties were investigated in terms of the physicochemical properties of starches. The lightness values of the eight sweet potato starches were higher than 90, which was satisfactory for starch purity. The average molecular weight (MW) and amylopectin average chain length (ACL) of sweet potato starches ranged from 6.93 × 107 g/mol to 16.57 × 107 g/mol and from 21.85% to 23.00%, respectively. Su16 starch with low amylose content and a large amount of short chains exhibited low crystallinity and thermal properties. These results suggested that the molecular structure of amylose and amylopectin was the main influencing factor in determining sweet potato starch physicochemical properties. The swelling power and water solubility of the starches ranged within 20.14-30.51 g/g and 5.28%-11.71% at 95 °C, respectively. Regarding pasting properties, all the starch samples presented high peak viscosity (>5500 cP) and peak temperature (>78 °C), indicating that sweet potato starch can be used as a thickener. All eight sweet potatoes varieties showed great application potential in the food industry.

Functional and physicochemical properties of flours and starches from different tuber crops.

Flours and isolated starches from different potato and sweet potato varieties were evaluated for their physical, functional, pasting, and thermal properties. The flours had higher protein and amylose contents than starches. The L values of the starches ranged from 91.92 (S-2) to 96.42 (S-1); thus, the whiteness of the starch samples was satisfactory. X-ray diffraction mode showed that potato starch could be a special material for crystalline nanomaterials with potential industrial applications. The starches had higher viscosity than flours. Therefore, starches can be used as thickeners in different food products. The flours exhibited high gelatinization temperatures but low enthalpy, which can be attributed to the effects of non-starch components in the flours, such as proteins and lipids. Potato flours and starches exhibited higher amylose contents and pasting characteristics and wider applications in the food industry than sweet potato flours and starches. The purple-fleshed varieties had high antioxidant activity. Therefore, the colorful flours of potatoes and sweet potatoes can be combined with other cereals for the development of functional flours with nutritional applications.

Effects of phosphate fertiliser on the physicochemical properties of Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) starch.

Phosphate fertilisation affects the growth, development and quality of Tartary buckwheat. In this study, the effect of different phosphorus levels, including 0, 15, 75, and 135 kg/ha (non-, low-, medium-, and high-phosphorus levels, respectively), on the characteristics of starch from Tartary buckwheat were investigated in 2015 and 2017. With increased phosphorus level, the median diameter of starch granules and the apparent amylose content initially decreased and then increased. All starch samples showed the features of A-type X-ray diffraction patterns. Starches under medium-phosphorus treatment showed higher relative crystallinity than those under non-phosphorus treatment, as well as the highest solubility, gelatinisation enthalpy and transmittance among all starches. Starches under low-phosphorus treatment exhibited higher pasting properties than those under non-phosphorus treatment. This research revealed that phosphorus treatments and year significantly affected the physicochemical properties of Tartary buckwheat starch, and can provide information for the applications of starch in the food and non-food industries.

Analysis of Flavonoid Metabolites in Buckwheat Leaves Using UPLC-ESI-MS/MS.

Flavonoids from plants are particularly important in our diet. Buckwheat is a special crop that is rich in flavonoids. In this study, four important buckwheat varieties, including one tartary buckwheat and three common buckwheat varieties, were selected as experimental materials. The total flavonoid content of leaves from red-flowered common buckwheat was the highest, followed by tartary buckwheat leaves. A total of 182 flavonoid metabolites (including 53 flavone, 37 flavonol, 32 flavone C-glycosides, 24 flavanone, 18 anthocyanins, 7 isoflavone, 6 flavonolignan, and 5 proanthocyanidins) were identified based on Ultra Performance Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry (UPLC-ESI-MS/MS) system. Through clustering analysis, principal component analysis (PCA), and orthogonal signal correction and partial least squares-discriminant analysis (OPLS-DA), different samples were clearly separated. Considerable differences were observed in the flavonoid metabolites between tartary buckwheat leaves and common buckwheat leaves, and both displayed unique metabolites with important biological functions. This study provides new insights into the differences of flavonoid metabolites between tartary buckwheat and common buckwheat leaves and provides theoretical basis for the sufficient utilization of buckwheat.

Effects of nitrogen level on the physicochemical properties of Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) starch.

Nitrogen is an essential nutrient for Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) because this substance affects the yield and quality of Tartary buckwheat. The physicochemical characteristics of starch represent the important parameters of Tartary buckwheat quality. The effects of different levels of nitrogen application at different levels (0, 45, 135 and 225kg/ha in 2015 and 0, 90, 180 and 270kg/ha in 2017) on the physicochemical characteristics of Tartary buckwheat starch were studied. The amylose content, particle size and retrogradation of Tartary buckwheat starch with nitrogen were lower than those of without nitrogen. The structure complexity, pasting temperature, gelatinization enthalpy, relative crystallinity, light transmittance and solubility of the former were higher than those of the latter. Nitrogen application did not change the 'A'-type crystalline pattern of Tartary buckwheat starch. This study indicated that nitrogen level and years and the interactions among nitrogen fertilizer levels and years significantly affected the physicochemical properties of Tartary buckwheat starch. These integrated results also provided information about the management of fertilization conditions to obtain starches with special properties for applications in food or nonfood industries.

Tartary buckwheat (Fagopyrum tataricum Gaertn.) starch, a side product in functional food production, as a potential source of retrograded starch.

A starch rich fraction is a side product in Tartary buckwheat processing. This study investigated the fractions that are of technological and nutritional interest. Tartary buckwheat starch granules had a diameter of 3-14 µm, and presented a typical type "A" X-ray diffraction pattern. They contained nearly 39.0% amylose. The solubility of Tartary buckwheat starch was much lower at 70-90 °C (ranging within 9.9-10.4% at 90 °C) than that in maize (up to 49.3%) and potato (up to 85.0%) starch. The starch of one variety of Tartary buckwheat had significantly lower solubility at 70 °C and 80 °C than that of common buckwheat. The starch peak viscosity and breakdown were higher and pasting time was shorter in Tartary buckwheat than in that of the starch of common buckwheat. Tartary buckwheat starch had unique pasting and physicochemical properties, and is thereby capable of being exploited as a suitable raw material of retrograded starch in food processing.