Vitamin C in fleshy fruits: biosynthesis, recycling, genes, and enzymes

L-ascorbic acid (vitamin C) is a plant secondary metabolite that has a variety of functions both in plant tissues and in the human body. Plants are the main source of vitamin C in human nutrition, especially citrus, rose hip, tomato, strawberry, pepper, papaya, kiwi, and currant fruits. However, in spite of the biological significance of L-ascorbic acid, the pathways of its biosynthesis in plants were fully understood only in 2007 by the example of a model plant Arabidopsis thaliana. In the present review, the main biosynthetic pathways of vitamin C are described: the L-galactose pathway, L-gulose pathway, galacturonic and myo-inositol pathway. To date, the best studied is the L-galactose pathway (Smyrnoff–Wheeler pathway). Only for this pathway all the enzymes and the entire cascade of reactions have been described. For other pathways, only hypothetical metabolites are proposed and not all the catalyzing enzymes have been identified. The key genes participating in ascorbic acid biosynthesis and accumulation in fleshy fruits are highlighted. Among them are L-galactose pathway proteins (GDP-mannose phosphorylase (GMP, VTC1), GDP-D-mannose epimerase (GME), GDP-L-galactose phosphorylase (GGP, VTC2/VTC5), L-galactose-1-phosphate phosphatase (GPP/VTC4), L-galactose-1-dehydrogenase (GalDH), and L-galactono1,4-lactone dehydrogenase (GalLDH)); D-galacturonic pathway enzymes (NADPH-dependent D-galacturonate reductase (GalUR)); and proteins, controlling the recycling of ascorbic acid (dehydroascorbate reductase (DHAR1) and monodehydroascorbate reductase (MDHAR)). Until now, there is no clear and unequivocal evidence for the existence of one predominant pathway of vitamin C biosynthesis in fleshy fruits. For example, the L-galactose pathway is predominant in peach and kiwi fruits, whereas the D-galacturonic pathway seems to be the most essential in grape and strawberry fruits. However, in some plants, such as citrus and tomato fruits, there is a switch between different pathways during ripening. It is noted that the final ascorbic acid content in fruits depends not only on biosynthesis but also on the rate of its oxidation and recirculation

5′-UTR allelic variants and expression of the lycopene-ɛ-cyclase <i>LCYE</i> gene in maize (<i>Zea mays</i> L.) inbred lines of Russian selection

In breeding, biofortification is aimed at enriching the edible parts of the plant with micronutrients. Within the framework of this strategy, molecular screening of collections of various crops makes it possible to determine allelic variants of genes, new alleles, and the linkage of allelic variants with morphophysiological traits. The maize (Zea mays L.) is an important cereal and silage crop, as well as a source of the main precursor of vitamin A – β-carotene, a derivative of the β,β-branch of the carotenoid biosynthesis pathway. The parallel β,ε-branch is triggered by lycopene-ε-cyclase LCYE, a low expression of which leads to an increase in provitamin A content and is associated with the variability    of the 5’-UTR gene regulatory sequence. In this study, we screened a collection of 165 maize inbred lines of Russian selection for 5’-UTR LCYE allelic variants, as well as searched for the dependence of LCYE expression levels on the 5’-UTR allelic variant in the leaves of 14 collection lines. 165 lines analyzed were divided into three groups carrying alleles A2 (64 lines), A5 (31) and A6 (70), respectively. Compared to A2, allele A5 contained two deletions (at positions -267–260 and -296–290 from the ATG codon) and a G251→T substitution, while allele A6 contained one deletion (-290–296) and two SNPs (G251→T, G265→T). Analysis of LCYE expression in the leaf tissue of seedlings from accessions of 14 lines differing in allelic variants showed no associations of the 5’-UTR LCYE allele type with the level of gene expression. Four lines carrying alleles A2 (6178-1, 6709-2, 2289-3) and A5 (5677) had a significantly higher level of LCYE gene expression (~0.018–0.037) than the other 10 analyzed lines (~0.0001–0.004), among which all three allelic variants were present

Balneohomeopathic Drugs Based on the Silt Sulphide Mud of Big Tambukan Lake

Purpose: To develop a method of complex application of antiulcer drug and mud-balneohomeopathic drugs in gastroduodenal pathology in combination with generalized periodontitis. Materials and methods: Surveillance of 100 patients with often relapsing ulcers and erosions of ezophagogastroduodenal area in combination with generalized periodontitis is conducted. Results: The positive dynamics of main indicators that characterize the disease process is 15-20% higher in patients treated with additional pelotherapy. The overall effectiveness of treatment is 62.3% in the first group of patients while in the second - 86.5% (p1-2 &lt;0.05). Summary: The use of mud-balneohomeo drugs in diseases of the gastroduodenal zone in combination with generalized periodontitis contributes to the overall effectiveness of treatment due to their pronounced immunomodulatory, antioxidant, and anti-inflammatory effects

Nomenclatural standards and genetic passports of potato cultivars bred in the A.G. Lorkh All-Russian Research Institute of Potato Farming

In order to preserve the genetic diversity of cultivars, it is recommended to develop documentation approaches through the registration of cultivar nomenclatural standards in accordance with the International Code of Nomenclature for Cultivated Plants. The N.I Vavilov Institute of Plant Genetic Resources keeps developing this approach along with the DNA marker technologies: SSR genotyping and molecular screening with DNA markers of genes controlling valuable traits. In 2018, VIR, together with the leading national centre for potato breeding – the A.G. Lorkh All-Russian Scientific-Research Institute of Potato Farming (now the A.G. Lorkh Russian Potato Research Center), initiated the preparation of nomenclatural standards for potato cultivars bred both at the A.G. Lorkh institute and in co-authorship with other breeding institutions. This paper presents 30 nomenclatural standards which are maintained in the Nomenclature standard fund of the Herbarium of cultivated plants and their wild relatives and weeds (VIR Herbarium, WIR). Also, the paper presents genetic passports of the mentioned 30 cultivars, developed using DNA samples extracted from the plant material of nomenclatural standards. Genetic passports include information about the polymorphism of the 8 chromosome-specific microsatellites and data on the results of molecular screening with 15 markers of 11 genes conferring resistance to the most dangerous pathogens and pests: potato viruses Y and X, late blight and potato cyst nematodes. A comparison of SSR-profiles of nomenclatural standards with those of 66 cultivar samples obtained from various sources made it possible to verify authenticity and homogeneity of the latter

Chromosome and Molecular Analyses Reveal Significant Karyotype Diversity and Provide New Evidence on the Origin of Aegilops columnaris

Aegilops columnaris Zhuk. is tetraploid grass species (2n = 4x = 28, UcUcXcXc) closely related to Ae. neglecta and growing in Western Asia and a western part of the Fertile Crescent. Genetic diversity of Ae. columnaris was assessed using C-banding, FISH, nuclear and chloroplast (cp) DNA analyses, and gliadin electrophoresis. Cytogenetically Ae. columnaris was subdivided into two groups, C-I and C-II, showing different karyotype structure, C-banding, and FISH patterns. C-I group was more similar to Ae. neglecta. All types of markers revealed significant heterogeneity in C-II group, although group C-I was also polymorphic. Two chromosomal groups were consistent with plastogroups identified in a current study based on sequencing of three chloroplast intergenic spacer regions. The similarity of group C-I of Ae. columnaris with Ae. neglecta and their distinctness from C-II indicate that divergence of the C-I group was associated with minor genome modifications. Group C-II could emerge from C-I relatively recently, probably due to introgression from another Aegilops species followed by a reorganization of the parental genomes. Most C-II accessions were collected from a very narrow geographic region, and they might originate from a common ancestor. We suggest that the C-II group is at the initial stage of species divergence and undergoing an extensive speciation process