Bread wheat producing grain in which the pericarp is purple is considered to be a useful source of dietary anthocyanins. The trait is under the control of the Pp-1 homoealleles (mapping to each of the group 7 chromosomes) and Pp3 (on chromosome 2A). Here, TaMyc1 was identified as a likely candidate for Pp3. The gene encodes a MYC-like transcription factor. In genotypes carrying the dominant Pp3 allele, TaMyc1 was strongly transcribed in the pericarp and, although at a lower level, also in the coleoptile, culm and leaf. The gene was located to chromosome 2A. Three further copies were identified, one mapping to the same chromosome arm as TaMyc1 and the other two mapping to the two other group 2 chromosomes; however none of these extra copies were transcribed in the pericarp. Analysis of the effect of the presence of combinations of Pp3 and Pp-1 genotype on the transcription behavior of TaMyc1 showed that the dominant allele Pp-D1 suppressed the transcription of TaMyc1.

Anthocyanins are plants secondary metabolites important for plant adaptation to severe environments and potentially beneficial to human health. Purple colour of barley grain is caused by the pigments synthesized in pericarp. One or two genes determine the trait. One of them is Ant2 mapped on chromosome 2HL and is known to encode transcription factor (TF) with a bHLH domain. In plants, bHLH regulates anthocyanin biosynthesis together with TF harboring an R2R3-MYB domain. In wheat, the R2R3-MYBs responsible for purple colour of grain pericarp are encoded by the homoallelic series of the Pp-1 genes that were mapped on the short arms of chromosomes 7. In barley, in orthologous positions to wheat’s Pp-1, the Ant1 gene determining red colour of leaf sheath has been mapped. In the current study, we tested whether Ant1 has pleiotropic effect not only on leaf sheath colour but also on pericarp pigmentation. А set of near isogenic lines (NILs) carrying different combinations of alleles at the Ant1 and Ant2 loci was created using markers-assisted backcrossing approach. The dominant alleles of both the Ant1 and Ant2 genes are required for anthocyanin accumulation in pericarp. A qRT-PCR analysis of the Ant genes in lemma and pericarp of the NILs revealed that some reciprocal interaction occurs between the genes. Expression of each of the two genes was up-regulated in purple-grained line with dominant alleles at the both loci. The lines carrying dominant allele either in the Ant1 or in the Ant2 locus were characterized by the decreased level of expression of the dominant gene and scant activity of the recessive one. The Ant1 and Ant2 expression was barely detected in uncolored line with recessive alleles at both loci. The anthocyanin biosynthesis structural genes were differently regulated: Chs, Chi, F3h, Dfr were transcribed in all lines independently on allelic state of the Ant1 and Ant2 genes, whereas F3’h and Ans were activated in presence on dominant alleles of the both regulatory genes. The R2R3-MYB-encoding counterpart (Ant1) of the regulatory Ant2 gene was determined for the first time. The dominant alleles of both of them are required for activation of anthocyanin synthesis in barley lemma and pericarp. The R2R3-MYB + bHLH complex activates the synthesis via affecting expression of the F3’h and Ans structural genes. In addition, positive regulatory loop between Ant1 and Ant2 was detected. Earlier the interaction between the anthocyanin biosynthesis regulatory genes has been revealed in dicot plant species only. Our data demonstrated that the regulatory mechanism is considered to be more common for plant kingdom than it has been reported so far.

Among the natural pigments, anthocyanins are assumed to represent one of the most studied groups. Starting with the first studies on the physicochemical properties of anthocyanins carried out in the 17th century by British naturalist Robert Boyle, the science about these unique compounds has progressed substantially. To date, the structure and functions of anthocyanins in plant cells have been well studied, and the pathway of their biosynthesis is one of the most fully characterized pathways of secondary metabolite biosynthesis at both the biochemical and genetic levels. Along with these fundamental achievements, we are beginning to realize the potential of anthocyanins as compounds of industrial importance, as pigments themselves, as well as components of functional food that contribute to the prevention and reduction of risk of chronic diseases. For a long time, the biological activity of anthocyanins has been underestimated, in particular, due to the data on their low bioavailability. However, studies showed that in humans and animals, these compounds are actively metabolized and the bioavailability, estimated taking into account their metabolites, exceeded 12 %. It has been experimentally shown that anthocyanins have antioxidant, anti-inflammatory, hypoglycemic, antimutagenic, antidiabetic, anti-cancer, neuroprotective properties, and they are beneficial for eye health. However, the studies conducted cannot always explain the molecular mechanism of action of anthocyanins in the human body. According to some reports, the observed effects are not due to the action of anthocyanins themselves, but to their metabolites, which can be more biologically active because of their increased bioavailability. Other data ascribe the positive effect on human health not to individual anthocyanins, but to the whole complex of polyphenolic compounds consumed. The review summarizes the results of the studies of anthocyanins as components of functional food. Special attention is paid to genetic control of the pigment synthesis. These data are of particular importance in respect to the initiated breeding programs aimed at increasing the content of anthocyanins in cultural plants.

In wheat, anthocyanin pigments can be accumulated in pericarp tissues (under control of the Pp genes) resulting in purple-colored grain. In the current study, a strategy, based on the use of molecular and morphological markers, was applied to create purple-grained bread wheat cultivars adapted to the West Siberian region. The breeding scheme started from crossing of recipients (elite cultivars and lines) with donor lines carrying dominant alleles of the complementary genes Pp3 and Pp-D1. The F₂ hybrids passed three-step marker-assisted selection, and those having dominant Pp-D1Pp-D1Pp3Pp3 genotypes were backcrossed with the recurrent parents. The desired BC₁F_2-3 progenies were selected using morphological marker, while BC₁F₃ also passed through field evaluation. At this stage, 120 lines were selected and planted in individual 1 m² “breeding nursery (BN) plots” for assessment of heading dates, duration of vegetation period, resistance to powdery mildew, stem and leaf rusts, protein and gluten content, as well as productivity. After these investigations, a total of 17 promising anthocyanin-rich purple-grained lines characterized by multiple resistance and having best yield/quality characteristics were finally candidates for selection of commercial cultivars adapted to the West Siberian climate and suitable for functional food production.

The colored grain of wheat (Triticum aestivum L.) contains a large number of polyphenolic compounds that are biologically active ingredients. The purpose of this work was a comparative metabolomic study of extracts from anthocyaninless (control), blue, and deep purple (referred to here as black) grains of seven genetically related wheat lines developed for the grain anthocyanin pigmentation trait. To identify target analytes in ethanol extracts, high-performance liquid chromatography was used in combination with Bruker Daltonics ion trap mass spectrometry. The results showed the presence of 125 biologically active compounds of a phenolic (85) and nonphenolic (40) nature in the grains of T. aestivum (seven lines). Among them, a number of phenolic compounds affiliated with anthocyanins, coumarins, dihydrochalcones, flavan-3-ols, flavanone, flavones, flavonols, hydroxybenzoic acids, hydroxycinnamic acids, isoflavone, lignans, other phenolic acids, stilbenes, and nonphenolic compounds affiliated with alkaloids, carboxylic acids, carotenoids, diterpenoids, essential amino acids, triterpenoids, sterols, nonessential amino acids, phytohormones, purines, and thromboxane receptor antagonists were found in T. aestivum grains for the first time. A comparative analysis of the diversity of the compounds revealed that the lines do not differ from each other in the proportion of phenolic (53.3% to 70.3% of the total number of identified compounds) and nonphenolic compounds (46.7% to 29.7%), but diversity of the compounds was significantly lower in grains of the control line. Even though the lines are genetically closely related and possess similar chemical profiles, some line-specific individual compounds were identified that constitute unique chemical fingerprints and allow to distinguish each line from the six others. Finally, the influence of the genotype on the chemical profiles of the wheat grains is discussed.

Breeding programs for purple wheat are underway in many countries but there is a lack of information on the effects of Pp (purple pericarp) genes on agronomic and quality traits in variable environments and along the product chain (grain-flour-bread). This study was based on unique material: two pairs of isogenic lines in a spring wheat cv. Saratovskaya-29 (S29) background differing only in Pp genes and grain color. In 2017, seven experiments were conducted in Kazakhstan, Russia, and Turkey with a focus on genotype and environment interaction and, in 2018, one experiment in Turkey with a focus on grain, flour, and bread quality. The effect of environment was greater compared to genotype for the productivity and quality traits studied. Nevertheless, several important traits, such as grain color and anthocyanin content, are closely controlled by genotype, offering the opportunity for selection. Phenolic content in purple-grained lines was not significantly higher in whole wheat flour than in red-colored lines. However, this trait was significantly higher in bread. For antioxidant activities, no differences between the genotypes were detected in both experiments. Comparison of two sources of Pp genes demonstrated that the lines originating from cv. Purple Feed had substantially improved productivity and quality traits compared to those from cv. Purple.