Alexander Kilchevsky

Molecular genetic mechanisms of the development of fruit and seed coloration in plants

The diverse coloration of plant fruits and seeds is determined by the presence of two important types of pigments, carotenoids (red, orange, yellow) and anthocyanins (purple, blue, red). They belong to two groups of secondary metabolites (isoprenoids and flavonoids). Recently, increased interest in the study of genetic mechanisms controlling coloration traits in plants is observed due to the antioxidant and antimicrobial properties of certain pigments and their colorless precursors consumed with plant food. The genes encoding enzymes required for successive transformations of the initial organic molecules in the final pigment compounds are referred to as the group of structural genes. The factors activating the expression of the structural genes and controlling the synthesis of certain pigments at a particular time in certain part of the plant are referred to as regulatory biosynthesis genes. The data accumulated in the field of plant genetics indicate that the interspecific and intraspecific diversity by the coloration traits (observed at the phenotypical level) is associated with regulatory genes. The creation of rich collections and accurate genetic models by the coloration traits in dicotyledonous and monocotyledonous plants in previous years, as well as the development of molecular genetic methods of plant research, allowed to study in detail the mechanisms of the genetic regulation of the synthesis of pigment compounds at the molecular level. In this article, the peculiarities of regulating carotenoid biosynthesis are illustrated on the example of their production in fruits of the Solanaceae family. Genetic regulation of the synthesis of different flavonoid pigments is demonstrated on the example of the study of the seed coloration in the Poaceae family plants. The prospects of the practical use of regulatory genes controlling the fruit and seed coloration are discussed in the final part of the work; specific examples of their use in breeding of vegetable and cereal crops are given.

Genetic bases of tomatо marker-assisted selection in Belarus

Abstract To develop tomato hybrids and varieties with a high fruit quality, we gradually solved the following tasks: development of DNA-marking methods for long shelf life genes; the genes modifying the biosynthesis of carotenoids and their composition; testing of the elaborated methods on the developed breeding material; the selection of samples with different allelic composition of fruit quality genes; the development of F1 hybrids using the method of successive crosses and their study; the selection of tomato forms by DNA-typing methods with target genes in F2 populations to develop valuable breeding samples; the study of carotenoids’ accumulation peculiarities and their inheritance. We used DNA-identification methods for fruit quality genes: nor, rin, norA (long shelf life), B, ogc, hp2dg, gf-3 (carotenoid content). The tomato hybrids, combining two pigment content genes and one long shelf life gene and the model forms with different combinations of fruit quality genes (B/rin/gf-3, B/rin/hp2dg; B /nor/gf-3, B /nor/hp2dg; оgc /rin/gf-3, оgc /rin/hp2dg; оgc /nor/gf-3, оgc /nor/hp2dg) in a homozygous state were developed. Use of the developed accessions with carotenoid content genes (ogc/hp2dg, B/hp2dg) as maternal forms and the accessions with complex fruit quality genes (ogc/hp2dg/nor, ogc/hp2dg/rin, B/hp2dg/nor, B/hp2dg/rin, ogc/gf-3/nor, ogc/gf-3/rin, B/gf-3/rin, B/gf-3/nor) as paternal forms for hybridization contributes to high accumulation of carotenoids and a lond period of fruit storability.

Association between Total Carotenoid Content of Maize Kernels ( Zea mays L.) and Polymorphic Site INDEL1 in PSY1 Gene

Maize is the only major cereal crop that can naturally accumulate appreciable levels of carotenoids which are the source of provitamin A. The association of the total carotenoid content in maize kernels with allelic variation PSY1 InDel1 was estimated. We used a collection of 54 maize genotypes of different ecogeographical origins, methods of PCR analysis, spectrophotometry, and statistical analysis in this study. The total carotenoid content of genotypes with a favorable allele of InDel1 is 0.60 mg/100 g, which is significantly higher than that of the samples with an unfavorable allele (0.43 mg/100 g). Thus, the use of PCR-based markers for PSY1 InDell polymorphism is a reliable method for identifying genotypes with high carotenoid accumulation in maize kernels.

A key enzyme of animal steroidogenesis can function in plants enhancing their immunity and accelerating the processes of growth and development

BackgroundThe initial stage of the biosynthesis of steroid hormones in animals occurs in the mitochondria of steroidogenic tissues, where cytochrome P450SCC (CYP11A1) encoded by the CYP11A1 gene catalyzes the conversion of cholesterol into pregnenolone – the general precursor of all the steroid hormones, starting with progesterone. This stage is missing in plants where mitochondrial cytochromes P450 (the mito CYP clan) have not been found. Generating transgenic plants with a mitochondrial type P450 from animals would offer an interesting option to verify whether plant mitochondria could serve as another site of P450 monooxygenase reaction for the steroid hormones biosynthesis.ResultsFor a more detailed comparison of steroidogenic systems of Plantae and Animalia, we have created and studied transgenic tobacco and tomato plants efficiently expressing mammalian CYP11A1 cDNA. The detailed phenotypic characterization of plants obtained has shown that through four generations studied, the transgenic tobacco plants have reduced a period of vegetative development (early flowering and maturation of bolls), enlarged biomass and increased productivity (quantity and quality of seeds) as compared to the only empty-vector containing or wild type plants. Moreover, the CYP11A1 transgenic plants show resistance to such fungal pathogen as Botrytis cinerea. Similar valuable phenotypes (the accelerated course of ontogenesis and/or stress resistance) are also visible in two clearly distinct transgenic tomato lines expressing CYP11A1 cDNA: one line (No. 4) has an accelerated rate of vegetative development, while the other (No. 7) has enhanced immunity to abiotic and biotic stresses. The progesterone level in transgenic tobacco and tomato leaves is 3–5 times higher than in the control plants of the wild type.ConclusionsFor the first time, we could show the compatibility in vivo of even the most specific components of the systems of biosynthesis of steroid hormones in Plantae and Animalia. The hypothesis is proposed and substantiated that the formation of the above-noted special phenotypes of transgenic plants expressing mammalian CYP11A1 cDNA is due to the increased biosynthesis of progesterone that can be considered as a very ancient bioregulator of plant cells and the first real hormone common to plants and animals.

Theoretical aspects of heterosis

The phenomenon of heterosis, known as the superior performance of hybrid organisms over their parents, has been exploited by agricultural practices in the production of various crops since the beginning of the last century; however, its genetic basis has remained obscure. With the experimental data obtained from the study of maize hybrids and mathematical calculations, some genetic models have been proposed to explain heterosis in terms of various types of gene interaction, such as dominance, overdominance, and epistasis. However, each of the proposed concepts has weak points, which impose limitations on the possibility of the overall interpretation of the heterotic response in F1. This review provides a critical assessment of the theoretical concepts of heterosis from the perspective of the currently accumulated data of genetics and molecular biology, which are focused on specific mechanisms acting for specific traits. In particular, the role of lethal and semi-lethal mutations in the formation of a heterotic phenotype in plants is shown. The issues of the interpretation of genetic effects in case of gene linkage, which are referred to as pseudo-overdominance, are considered. Particular attention is paid to nonallelic interactions of genes, which add new nuances when discussing the effects of dominance and overdominance. Information on combining ability and its practical use in the context of the concept of heterotic groups is presented. Some aspects of the genotype–environment interaction are shown. The analysis of the theoretical concepts of heterosis from the perspective of modern genetic data testifies to the important role of various types of gene action in the formation of an outstanding phenotype and confirms the need for a systematic approach to this complex and unique phenomenon.

Marker-assisted identification of maize genotypes with improved protein quality

Currently, more than 70% of maize is used for food and fodder; therefore, an improvement in grain quality can increase its nutritive and energy value. A deficiency of two essential amino acids (lysine and tryptophan) significantly reduces the nutritional quality of maize proteins. However, in comparison to conventional maize varieties, opaque2 (o2) mutants have greater contents of lysine and tryptophan in their endosperm proteins and their bioavailability is better. The aim of the study was to identify the maize accessions with high-quality protein. A collection of maize accessions of various ecogeographical origins was studied by molecular methods. This approach was expected to improve the maize’s breeding efficiency. We collected 54 maize genotypes differing in grain quality performance. Amplification with three specific markers for the opaque-2 gene (phi057, phi112, and umc1066) revealed homozygous recessive o2 genotypes associated with an improved nutritional quality of the protein. UREA-PAG electrophoresis of zein proteins was used for Quality Protein Maize (QPM) identification. In addition to the mutant o2 allele, QPM contains genetic modifiers that convert the starchy endosperm of the o2 mutant to the hard vitreous phenotype. The selected QPM accessions are of interest for maize breeding programs aimed at improving grain quality. The use of the markers for o2 and modifier genes accelerates the development of QPM varieties and significantly reduces the labor and financial costs of their production.