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- Author or Editor: E. Khlestkina x
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The flavonoid biosynthesis pathway yields a large family of phenolic compounds which are involved in many biological activities including plant defense response to a broad spectrum of abiotic and biotic stress factors. In recent years, a wide range of evidences of relationship between the flavonoid biosynthesis and stress has been accumulated based on genetic, physiological and biochemical studies. In this paper, possible mechanisms of counteraction of flavonoid substances to different stress factors are reviewed, and the evidences for relationship between biosynthesis of flavonoid compounds and response to biotic and abiotic stress are summarized with emphasis on cereals.
Nine wheat genotypes differing by Rc (red coleoptile) alleles were investigated for the dynamics of seedling growth and relative anthocyanin content in the coleoptiles in response to cold. The stressed genotypes showed either reduced, similar or increased anthocyanin content compared to unstressed plants. This difference can be partially explained by the allelic state of the Rc genes. In ‘Saratovskaya 29’ weak Rc allele causes low anthocyanin content under optimal growth conditions. Upon cold treatment the level of anthocyanins decreased, whereas it increased in two near isogenic lines (NILs) with strong Rc alleles developed on ‘Saratovskaya 29’, and in some other genotypes having high anthocyanin content under optimal growth conditions. The changes in anthocyanin content correlated negatively with the changes of growth parameters in response to cold stress, suggesting the presence of some stress-dependent regulation of anthocyanin biosynthesis in wheat coleoptiles.
Due to anthropogenic activity, the environment is contaminated with high levels of cadmium, which is a dangerous heavy metal. At very low concentrations, cadmium is bioaccumulative and toxic to animals and plants, generating reactive oxygen species (ROS) that are destructive to cells of organisms. Anthocyanin pigments are natural antioxidants produced in various plant tissues and play a protective role under different environments. In the present study, the putative role of anthocyanins that accumulate in the grains and shoots of bread wheat (Triticum aestivum L.) in response to cadmium-induced toxicity (25 and 50 μM CdCl2) was studied at the seedling stage. For this purpose, a set of near-isogenic lines carrying different alleles of the Pp (purple pericarp) and Rc (red coleoptile) genes was used. The lines responded differently to Cd treatment. The observed changes in anthocyanin metabolism under stress conditions were dependent on the alleles of the Rc genes that determine coleoptile pigmentation and on CdCl2 concentration. In less-colored line carrying the Rc-A1 allele, the antioxidant system was unable to fully cope with oxidative stress and thus induced the synthesis of additional antioxidants, whereas in the most tolerant lines, which have darkpurple coleoptile pigmentation predetermined by Rc-A1 + Rc-D1, the level of anthocyanins in the coleoptiles was independent of stress. A protective role of anthocyanins presented in the coleoptiles of wheat seedlings was observed under moderate Cd stress (25 μM), whereas anthocyanins seemed to be ineffective as protective compounds under heavier stress.
Purple colour of wheat grain is determined by anthocyanin accumulation in the pericarp. This trait is controlled in hexaploid Triticum aestivum or tetraploid T. durum wheats by two complementary dominant genes Pp1 (chromosome 7B) and Pp3 (chromosome 2A). It remained unclear, whether functional alleles of one of the two complementary Pp genes occur in the diploid progenitors of allopolyploid wheat or in tetraploid T. timopheevii. In the current study, a purple-grained wheat line PC was obtained by crossing non-purple-grained T. aestivum Line 821 and Line 102/00i carrying introgressions from T. timopheevii and Aegilops speltoides, respectively. Crosses of lines 821 and 102/00i with a number of tester lines and cultivars did not result in purple-grained genotypes suggesting that expression of this trait in PC was controlled by complementary factors, one located in the T. timopheevii introgression and the other in the introgression inherited from Ae. speltoides. Genotyping of PC and other parental lines using microsatellite markers located on wheat chromosomes 7B and 2A showed that PC carries chromosome 7S of Ae. speltoides substituting for chromosome 7B, whereas chromosome 2A of PC contains an extended introgression from T. timopheevii.
Previously, it was suggested that purple grain colour was transferred to bread wheat from purple-grained tetraploid T. durum. In the current study, we demonstrated that the D genome of bread wheat ‘Purple’ carries one of two complementary genes determining purple grain colour. This gene was mapped on the short arm of chromosome 7D 2.5 cM distal to the locus Rc-D1 determining red coleoptile colour. This position is highly comparable with that of the Pp1 gene mapped earlier on the short arm of chromosome 7B in tetraploid T. durum.We suggest the Pp genes on T. durum chromosome 7B and T. aestivum chromosome 7D are orthologous. We designated them Pp-B1 and Pp-D1, respectively. Microsatellite-based genotyping of near-isogenic lines ‘i:S29Pp1Pp2PF’ and ‘i:S29Pp1Pp3P’, their recurrent (T. aestivum ‘Saratovskaya 29’) and donor (T. aestivum ‘Purple Feed’ and ‘Purple’, respectively) parents showed the presence of donor introgressions on chromosomes 2A and 7D in both near-isogenic lines. In addition to previously described purple pericarp, anthers and culms, phenotyping of these lines in the current study showed dark red coleoptile colour (with anthocyanin contents four times higher than in ‘Saratovskaya 29’ coleoptiles) and purple leaf blade and leaf sheath colour. It was concluded that each of the lines ‘i:S29Pp1Pp2PF’ and ‘i:S29Pp1Pp3P’ carry clusters of genes Rc-D1, Pc-D1, Pan-D1, Plb-D1, Pls-D1 and Pp-D1 on chromosome 7D between microsatellite markers Xgwm0044 and Xgwm0676.
A segregation test confirmed that the genes present on chromosome 1A encoding red and black glumes are allelic to one another. Similarly, the chromosome 1D genes for smokey-grey and red glume coloration are allelic. Consensus maps of chromosomes 1A and 1D carrying Rg-A1 and Rg-D1 , respectively, were derived from extant genotypic data. The Gli-B1 associated microsatellite MW1B002 mapped 2cM proximal from Rg-B1 . The association of red glume coloration with specific MW1B002 alleles is described for a set of Russian, Albanian, Indian and Nepalese bread wheats.
Two bread wheat crosses were used to genetically map the genes determining anthocyanin pigmentation of the anther (Pan-D1) , culm ( Pc-B1 and Pc-D1 ), leaf sheath (Pls-B1) , and leaf blade (Plb-B1, Plb-D1) . The genes cluster with Rc-1 (red coleoptile) on chromosome arms 7BS and 7DS. A germplasm panel of 37 wheat cultivars and introgression lines was tested for the presence of anthocyanin pigmentation on various plant organs, and significant correlations were established between pigmentation of the coleoptile and culm, coleoptile and leaf blade, coleoptile and anther, and anther and leaf blade.
Anthocyanin accumulation in vegetative organs has a relationship to stress resistance in plants. In wheat, ability to accumulate anthocyanins in the coleoptile is inherited and controlled by the Rc (red coleoptile) genes. The aim of the current study was to find potential sources of ‘strong’ Rc alleles conferring very high levels of anthocyanin production and to study the effect of genetic background on Rc expression. We measured the relative anthocyanin content (OD530) in the coleoptile of different wheat and wheat-alien genetic stocks and accessions to find potential sources of ‘strong’ Rc alleles conferring very high levels of anthocyanin production. The OD530 values varied from 0.514 to 3.311 in genotypes having red coleoptiles. The highest anthocyanin content was detected in coleoptiles of four Triticum dicoccoides accessions originating from Israel and the Russian T. aestivum cultivar ‘Novosibirskaya 67’, suggesting that their Rc alleles can be used to increase anthocyanin content in the coleoptile of wheat cultivars. It is also suggested that rye Rc alleles, such as that of Russian cultivar ‘Selenga’, can be used to increase anthocyanin content in triticale seedlings.
Anthocyanins are natural antioxidants able to scavenge free radicals, which appear in plant cells under various environmental stresses. In wheat, anthocyanin pigments can be synthesized in vegetative and reproductive organs. The objective of the current study was to estimate the significance of these substances for wheat seedlings protection under irradiation stress (after treatment of dry seeds with moderate doses of gamma-irradiation, 50, 100 and 200 Gy). For this goal a set of near-isogenic lines (8 NILs) carrying different combinations of the Pp (purple pericarp) and Rc (red coleoptile) alleles were used. The effect of gammairradiation on the growth parameters and anthocyanin content in coleoptiles was studied at the 4th day after germination. The germination rate was not affected, while roots’ and shoots’ lengths and fresh weights as well as root number decreased significantly under irradiation treatment. The effect was deeper under higher doses. Irradiation treatment also induced change of root morphology (‘hairy roots’). The effect of treatment on coleoptile anthocyanin content depended on allelic combination at the Rc loci. At the presence of ‘weak’ Rc-A1 allele anthocyanin content decreased, while it did not change in lines with Rc-A1 + Rc-D1 combination (NILs with intensively colored coleoptiles). Factors ‘pericarp color’ and ‘coleoptile color’ influenced vigor of the seedlings under 50 Gy, whereas under higher doses (100 and 200 Gy) these factors did not contribute to growth parameters changes. Statistically significant positive effect of anthocyanins synthesized in coleoptile (in the presence of Rc-A1 + Rc-D1 dominant alleles) on root growth of seedling germinated from 50 Gy-treated seeds was observed.
Plant secondary metabolites anthocyanins are considered to play a protective role. In bread wheat (Triticum aestivum L.), anthocyanins can be observed in both adult plants and seedlings. The aim of the current study was to investigate the putative role of anthocyanins present in grains and shoots with respect to the protection of seedlings against drought. For this purpose a set of near isogenic lines (NILs) differing in pericarp and coleoptile colour was used. Water stress was created by artificial shortage of moisture under laboratory conditions. Differences among the lines were observed in a way that the lines with dark-purple grains and coleoptiles (genotype Pp-D1Pp-D1Pp3Pp3Rc-A1Rc-A1Rc-D1Rc-D1) demonstrated a higher seedling drought tolerance than plants with uncoloured pericarp and lightpurple coleoptiles (pp-D1pp-D1pp3pp3Rc-A1Rc-A1rc-D1rc-D1). Furthermore, protection of the root system and the shoot was related with the presence of anthocyanins in grains and coleoptiles, respectively.