Quantitative characteristics of pubescence in wheat (Triticum aestivum L.) are associated with photosynthetic parameters under conditions of normal and limited water supply

Density and length of leaf pubescence are important factors of diversity in the response to water deficiency among wheat genotypes. Many studies evidence an important protective value of leaf hairiness in plants, especially under the conditions of drought, thermal loads and increased solar radiation. However, the physiological and adaptive roles of such traits in cereals, including cultivated plants, have not been sufficiently studied to date. The aim of this work was to study the association of morphological characteristics of leaves with parameters of gas exchange and chlorophyll fluorescence in wheat lines carrying a genetically different leaf hairiness. Isogenic and inter-varietal substitution wheat lines were used, carrying various combinations of dominant and recessive alleles of the known genes. A quantitative assessment of the pubescence was carried out in contrasting watering conditions to establish the physiological role of this trait in adaptation to drought. With the help of a portable system for studying the gas exchange and chlorophyll fluorescence, ten parameters of photosynthesis were studied, as well as morphological features of leaves and shoot biomass. It was found that gas exchange parameters are inversely proportional to the density and length of trichomes. In drought conditions, the trichome density increased and the length of trichomes decreased under the observed decrease in the level of gas exchange. A similar dependence was observed for the level of non-photochemical quenching of chlorophyll fluorescence. Under optimal conditions, the poorly haired cultivars exhibited a higher biomass than the densely haired. However, under water deficiency they significantly reduced the biomass and showed a low value of the tolerance index.

Regions of the bread wheat D genome associated with variation in key photosynthesis traits and shoot biomass under both well watered and water deficient conditions

A quantitative trait locus (QTL) approach was taken to reveal the genetic basis in wheat of traits associated with photosynthesis during a period of exposure to water deficit stress. The performance, with respect to shoot biomass, gas exchange and chlorophyll fluorescence, leaf pigment content and the activity of various ascorbate-glutathione cycle enzymes and catalase, of a set of 80 wheat lines, each containing a single chromosomal segment introgressed from the bread wheat D genome progenitor Aegilops tauschii, was monitored in plants exposed to various water regimes. Four of the seven D genome chromosomes (1D, 2D, 5D, and 7D) carried clusters of both major (LOD >3.0) and minor (LOD between 2.0 and 3.0) QTL. A major QTL underlying the activity of glutathione reductase was located on chromosome 2D, and another, controlling the activity of ascorbate peroxidase, on chromosome 7D. A region of chromosome 2D defined by the microsatellite locus Xgwm539 and a second on chromosome 7D flanked by the marker loci Xgwm1242 and Xgwm44 harbored a number of QTL associated with the water deficit stress response.

Ortho-phthalic acid esters in lipophilic extract from the cell culture of Aconitum baicalense Turcz ex Rapaics 1907

Optically active bis-2R(-)ethylhexyl o-phthalate was obtained with 0.18% yield from dry cultured cells of Aconitum baicalense Turcz ex Rapaics 1907 by extraction with petroleum ether followed by silica gel column chromatography. Its structure was confirmed by the analysis of ¹³C and ¹H NMR spectra. Seasonal fluctuations of quantitative phthalate content in A. baicalense cells were identified. The tests were performed under conditions excluding the presence of phthalates in reagents, materials, and laboratory dishes. The same substance was shown to be produced by cultivated cells of other plants. Biosynthesis of esters of ortho-phthalic acid by cultivated plant cells was discovered for the first time.

Characteristics of Thiol:Protein Disulfide Oxidoreductase from Wheat (Triticum aestivum L.) Grain

Biochemical properties of a homogenous preparation of thiol:protein disulfide oxidoreductase (TPDO, EC 1.8.4.2) isolated for the first time from mature wheat (Triticum aestivum L.) grain were studied. According to polyacrylamide gel electrophoresis data, the molecular weight of TPDO is around 167 kD, the enzyme consisting of two subunits of 77 and 73 kD, which differentiates TPDO from known enzymes of SH/SS-metabolism of wheat caryopses. In substrate specificity and enzymatic characteristics (pH and temperature optima) TPDO is similar to analogous enzymes of animal tissues. Inhibition of disulfide reductase activity by alkylating agents and heavy metal ions suggests the participation of active center SH-groups in the catalytic act and classes the enzyme as a member of the thioredoxin superfamily. The SS-reductase reduces aggregating capacity of acetic acid-soluble fraction of wheat storage proteins. The proposed physiological role of TPDO is participation in creation and regulation of SH/SS-status of wheat endosperm proteins and formation of the rheological properties of gluten.

Physiological responses to water deficiency in bread wheat (Triticum aestivum L.) lines with genetically different leaf pubescence

Studying the relationship between leaf pubescence and drought resistance is important for assessing Triticum aestivum L. genetic resources. The aim of the work was to assess resistance of common wheat genotypes with different composition and allelic state of genes that determine the leaf pubescence phenotype. We compared the drought resistance wheat variety Saratovskaya 29 (S29) with densely pubescent leaves, carrying the dominant alleles of the Hl1 and Hl3 genes, and two near isogenic lines, i: S29 hl1, hl3 and i: S29 Hl2aesp, with the introgression of the additional pubescence gene from diploid species Aegilops speltoides. Under controlled conditions of the climatic chamber, the photosynthetic pigments content, the activity of ascorbate-glutathione cycle enzymes and also the parameters of chlorophyll fluorescence used to assess the physiological state of the plants photosynthetic apparatus were studied in the leaves of S29 and the lines. Tolerance was evaluated using the comprehensive index D, calculated on the basis of the studied physiological characteristics. The recessive state of pubescence genes, as well as the introduction of the additional Hl2aesp gene, led to a 6-fold decrease in D. Under the water deficit influence, the fluorescence parameters profile changed in the lines, and the viability index decreased compared with S29. Under drought, the activity of ascorbate peroxidase, glutathione reductase and dehydroascorbate reductase in the line i: S29 hl1, hl3 decreased 1.9, 3.3 and 2.3 times, in the line i: S29 Hl2aesp it decreased 1.8, 3.6 and 1.8 times respectively, compared with S29. In a hydroponic greenhouse, line productivity was studied. Compared with S29, the thousand grains mass in the line i: S29 hl1, hl3 under water deficit was reduced. The productivity of the line i: S29 Hl2aesp was significantly reduced regardless of water supply conditions in comparison with S29. Presumably, the revealed effects are associated with violations of cross-regulatory interactions between the proteins of the trichome formation network and transcription factors that regulate plant growth and stress response.

Regions of Chromosome 2A of Bread Wheat (Triticum aestivum L.) Associated with Variation in Physiological and Agronomical Traits under Contrasting Water Regimes

Understanding the genetic architecture of drought tolerance is of great importance for overcoming the negative impact of drought on wheat yield. Earlier, we discovered the critical role of chromosome 2A for the drought-tolerant status of wheat spring cultivar Saratovskaya 29. A set of 92 single-chromosome recombinant double haploid (SCRDH) lines were obtained in the genetic background of Saratovskaya 29. The lines carry fragments of chromosome 2A from the drought-sensitive cultivar Yanetzkis Probat. The SCRDH lines were used to identify regions on chromosome 2A associated with the manifestation of physiological and agronomical traits under distinct water supply, and to identify candidate genes that may be associated with adaptive gene networks in wheat. Genotyping was done with Illumina Infinium 15k wheat array using 590 SNP markers with 146 markers being polymorphic. In four identified regions of chromosome 2A, 53 out of 58 QTLs associated with physiological and agronomic traits under contrasting water supply were mapped. Thirty-nine candidate genes were identified, of which 18 were transcription factors. The region 73.8-78.1 cM included the largest number of QTLs and candidate genes. The variation in SNPs associated with agronomical and physiological traits revealed among the SCRDH lines may provide useful information for drought related marker-assisted breeding.