Relationships between puroindoline A-prolamin interactions and wheat grain hardness

Wheat grain proteins: Past, present, and future

Background and Objectives

Research on wheat grain proteins is reviewed, including achievements over the past century and priorities for future research. The focus is on three groups of proteins that have major impacts on wheat quality and utilization: the gluten proteins which determine dough viscoelasticity but also trigger celiac disease in susceptible individuals, the puroindolines which are major determinants of grain texture and the amylase/trypsin inhibitors which are food and respiratory allergens and are implicated in triggering celiac disease and nonceliac wheat sensitivity.

Findings

Although earlier work focused on protein structure and properties, the development of genomics and high-sensitivity proteomics has resulted in the availability of a vast amount of information on the amino acid sequences of individual wheat proteins, including allelic variants of gluten proteins which are associated with good processing quality and of puroindolines, which are associated with a hard or soft grain texture, and on protein expression and polymorphism.

Conclusions

However, our ability to exploit this knowledge is limited by a lack of detailed understanding of the structure:function relationships of wheat proteins. In particular, we need to understand how the three-dimensional structures of the individual proteins determine their interactions with other grain components (to determine functional properties) and with the immune systems of susceptible consumers (to trigger adverse responses), how these interactions are affected by allelic variation, and how they can be manipulated.

Significance and Novelty

The article, therefore, identifies priorities for future research which should enable the adoption of a more rational approach to improving the quality of wheat grain proteins.

Features and Possible Applications of Plant Lipid-Binding and Transfer Proteins

In plants, lipid trafficking within and inside the cell is carried out by lipid-binding and transfer proteins. Ligands for these proteins are building and signaling lipid molecules, secondary metabolites with different biological activities due to which they perform diverse functions in plants. Many different classes of such lipid-binding and transfer proteins have been found, but the most common and represented in plants are lipid transfer proteins (LTPs), pathogenesis-related class 10 (PR-10) proteins, acyl-CoA-binding proteins (ACBPs), and puroindolines (PINs). A low degree of amino acid sequence homology but similar spatial structures containing an internal hydrophobic cavity are common features of these classes of proteins. In this review, we summarize the latest known data on the features of these protein classes with particular focus on their ability to bind and transfer lipid ligands. We analyzed the structural features of these proteins, the diversity of their possible ligands, the key amino acids participating in ligand binding, the currently known mechanisms of ligand binding and transferring, as well as prospects for possible application.

The Influence of Farming Systems, Genotype and Their Interaction on Bioactive Compound, Protein and Starch Content of Bread and Spelt Wheat

An increase in the production and consumption of spelt products can be associated with positive effects on human health, which are attributed to bioactive compounds present in the grain. The basic success of spelt wheat in organic farming might be explained by the fact that spelt wheat belongs to the group of hulled wheat where the presence of a husk protects the seed from abiotic and biotic stress factors, thus demanding less chemical protection. The goal of this study was to investigate the variations in the bioactive compound (alkylresorcinol, arabinoxylan, β-glucan), protein, starch and fructan content of bread and spelt wheat under different farming systems (conventional and organic). The results showed higher protein and alkylresorcinol but lower fructan content in spelt wheat. Organic spelt had significantly higher starch, fiber and alkylresorcinol content but lower β-glucan and protein content than conventionally grown spelt. The spelt variety 'Oberkulmer-Rotkorn' was characterized by the highest values for the majority of analyzed traits under both farming systems. Overall, the environmental conditions (Hungary and Serbia), farming systems (conventional and organic) and wheat species (bread and spelt) contributed to the variations of the compositional traits in different manners.

The potential of plant proteins as antifungal agents for agricultural applications

Fungal pathogens induce a variety of diseases in both plants and post-harvest food crops, resulting in significant crop losses for the agricultural industry. Although the usage of chemical-based fungicides is the most common way to control these diseases, they damage the environment, have the potential to harm human and animal life, and may lead to resistant fungal strains. Accordingly, there is an urgent need for diverse and effective agricultural fungicides that are environmentally- and eco-friendly. Plants have evolved various mechanisms in their innate immune system to defend against fungal pathogens, including soluble proteins secreted from plants with antifungal activities. These proteins can inhibit fungal growth and infection through a variety of mechanisms while exhibiting diverse functionality in addition to antifungal activity. In this mini review, we summarize and discuss the potential of using plant antifungal proteins for future agricultural applications from the perspective of bioengineering and biotechnology.

Interrelating Grain Hardness Index of Wheat with Physicochemical and Structural Properties of Starch Extracted Therefrom

To investigate the physicochemical, structural, and rheological characteristics of starch from wheat cultivars varying in grain hardness index employed in making jiuqu and to interrelate grain hardness index with physicochemical and structural properties of starch. Starch extracted therefrom was investigated for structural and physicochemical properties. Starch granules showed relatively wide granule size distribution; large size granules showed lenticular shapes while medium and small size granules exhibited spherical or irregular shapes. Starch from wheat with a lower grain hardness index exhibited a relatively higher degree of crystallinity. Chain-length profiles of amylopectin showed distinct differences; among the fractions of fa, fb₁, fb_2, and fb₃ representing the weight-based chain-length proportions in amylopectin, the fa fractions ranged from 19.7% to 21.6%, the fb₁ fractions ranged from 44.4% to 45.6%, the fb₂ fractions ranged from 16.2% to 17.0%, and the fb₃ fractions ranged from 16.1% to 18.8%, respectively. T_o, T_p, T_c, and ∆H of starch ranged from 57.8 to 59.7 °C, 61.9 to 64.2 °C, 67.4 to 69.8 °C, and 11.9 to 12.7 J/g, respectively. Peak viscosity, hot pasting viscosity, cool pasting viscosity, breakdown, and setback of starch ranged from 127 to 221 RVU, 77 to 106 RVU, 217 to 324 RVU, 44 to 116 RVU, and 137 to 218 RVU, respectively. Both G’ and G” increased in the frequency range of 0.628 to 125.6 rad/s; the wheat starch gels were more solid-like during the whole range of frequency sweep.

Differences in Processing Quality Traits, Protein Content and Composition between Spelt and Bread Wheat Genotypes Grown under Conventional and Organic Production

The unique rheological properties of bread wheat dough and the breadmaking quality of its flour are the main factors responsible for the global distribution and utilization of wheat. Recently, interest in the production and expansion of spelt wheat has been boosted due to its significance in the production of healthy food, mostly originated from organic production. The aim of this study was to examine and compare quality parameters (gluten content, Zeleny sedimentation volume, farinograph dough properties), protein content and composition (by the Dumas method, Size Exclusion (SE) and Reversed Phase (RP) High Performance Liquid Chromatography (HPLC) analyses) of five bread and five spelt wheat varieties grown under conventional and organic production in Hungary and under conventional production in Serbia. Most of the analyzed traits showed significant differences between varieties, wheat species and growing sites. Total protein content was significantly higher in spelt than in bread wheat and under conventional than under organic production. In comparison to spelt, bread wheat showed better breadmaking quality, characterized by a higher amount of glutenins (in particular high molecular weight glutenin subunits) and unextractable polymeric proteins. The proportion of the gliadins was also found to be different under conventional and organic systems. Spelt Ostro and Oberkulmer-Rotkorn and bread wheat varieties Balkan, Estevan and Pobeda proved suitable for low input and organic systems.