Vol 64, No 1 (2017)

To determine the effects of physiological and genetic interaction between the genotype and environment, QTL (quantitative trait loci) mapping of valuable traits of bread wheat (Triticum aestivum L.) manifesting under controlled conditions of an agroecobiological testing ground has been first carried out. In the course of two experiments, differing from each other only by temperature and illumination regimes and providing the strict control and invariability of other growing parameters, 99 QTLs determining 30 different agronomically important traits have been identified. According to the results of the QTL mapping and a single-factor ANOVA, changes in the temperature and illumination regimes did not influence 21 of 30 studied traits, which remained stable in their manifestation; only nine traits varied under these conditions, which indicates that their manifestation is dependent on changes in these environmental factors. Both statistical approaches used in this study demonstrated complementary results; for each of them, the maximum likelihood criterion was used, statistical significance was determined, and significance of results was evaluated. The significance of a correlation between the identified QTLs and the polymorphism of individual traits studied was assessed using the threshold value of LOD (logarithm of odds) score. In addition, QTL analysis allowed a block structure of the T. aestivum genome to be revealed, the percentage of a phenotypic variability determined by each of the identified QTLs to be calculated, and the determination of which of the parents donated individual QTL alleles. The obtained results can be used for the further study of the physiological and genetic mechanisms of realization of traits evaluated within the framework of the “genotype–environment” interaction and also for the marker-assisted breeding of wheat.

Quantitative trait loci (QTLs) associated with the phenotypic expression of the activity of different forms of lipoxygenase (LOX) under water deficit were detected in the chromosomes of the D-genome using intogression lines of common wheat Triticum aestivum L. Chinese Spring (Synthetic 6x). QTL associated with the activity of seed soluble LOX was identified on the short arm of chromosome 4D. The activity of membranebound form of enzyme in the seedlings was mapped to the short arm, while that of a soluble form was on the long arm of chromosome 5D. Two regions responsible for the activity of soluble LOX in the leaves were found on the short arm of chromosome 2D. Three QTLs associated with the activities of chloroplast LOXs were found on the same chromosome: the activity of the soluble form was linked to Xgwm261 and Xgwm539 markers, and the membrane form to Xgdm93 marker. QTLs for the activities of both soluble and membrane-bound LOX in the leaves were identified in the centromeric region of chromosome 7D. The activities of two membrane enzymes in the leaves were linked to Xgdm130 marker on the short arm of this chromosome. Loci associated with the activity of different LOX forms colocalized with QTLs for the shoot mass, gas exchange parameters, chlorophyll fluorescence, content of photosynthetic pigments, and grain productivity of wheat. A correlation between these parameters and the LOX activity was detected and it was shown that various forms of the enzyme were differentially involved in the adaptation of wheat plants to water deficit. The current paper discusses their presumed physiological role.

Stevia rebaudiana Bertoni is known to the scientific world for its sweetness and steviol glycosides. Steviol glycosides are the secondary metabolites responsible for the sweetness of stevia and have many medical applications. They are synthesized by a biosynthesis pathway operating in the leaves. Stevioside (Stev) and rebaudioside A (Reb A) are two main glycosides compounds of Stevia. Translation products of three Uridine diphosphate glycosyltransferase candidate genes, UGT85C2, UGT74G1 and UGT76G1, were found to have an activity towards the synthesis of Stev and Reb A. In this study, a experiment was designed to measure the expression level of three candidate genes contributing to the biosynthesis of steviol glycosides under three different irrigation intervals using quantitative real-time PCR analysis technique. Irrigation was done at 3, 6 and 9 days irrigation intervals, based on soil moisture content 90, 75 and 60% of field capacity (FC) respectively. The results showed that soil water depletion up to 75% FC lead to significant increase in expression of UGT85C2 and UGT74G1 genes, whereas a significant growth in expression of UGT76G1 gene occurred at 60% FC. Measurement of Reb A contents in treated leaves showed that a significant correlation between UGT76G1 transcription and Reb A accumulation under 60% FC. Also, the comparison of expression patterns of the three target UGT transcripts at 75 and 60% FC showed a highly significant difference in UGT74G1 transcripts in comparison of UGT85C2 and UGT76G1 transcripts. These results indicated that the highest value of Reb A/ Stev ratio as sweetness quality index likely belongs to 60% FC and suggested 9 days irrigation intervals to improve the quantity and quality of glycoside profile by up-regulation and down-regulation of mentioned genes.

The hydrophilic water-soluble chlorophyll binding proteins (WSCP) which form complex with chlorophyll molecules have been numerously isolated from the chloroplasts of plants. Although, their molecular properties have been partly characterized, but their physio-biochemical roles are still unclear in the photosynthesizing organs. In this study, using bioinformatic tools WSCP pair were predicted to act as hydrolase and hydrolase inhibitor towards chlorophyll molecules. To enhance our information regarding the possible functions of WSCP, we cloned WSCP1 and WSCP2 cDNAs from Chenopodium album L. and Brassica oleracea L. leaves and expressed them as soluble maltose-binding fusion proteins in Escherichia coli. The purified fused products were subjected to chlorophyll hydrolyzing activity in vitro. The results showed that WSCP1 and WCSP2 are antagonistically involved in chlorophyll breakdown, while WSCP1 acts as chlorophyll hydrolyzing enzyme (with the hydrolysis rate of about 40% per 12 h), WSCP2 exerts inhibitory activity (with the inhibition rate of about 38% per 12 h) towards chlorophyll hydrolysis. This is the first ever time report speculates the hydrolase/inhibitory roles for WSCP and proposes that the relative activity of WSCP pair might balance and regulate the chlorophyll breakdown process in the photosynthetic apparatus of plants. It may open the new gate to investigate the potent roles of WSCP in plant system.

Aim of the present study was to determine differential responses in growth and physiology of tolerant (cv. IGPN 2004) and sensitive (cv. GA 10) cultivars of Niger (Guizotia abyssinica Cass.) using in vitro grown calli under water deficit conditions. The calli were subjected to drought stress using PEG-8000 (–0.16,–0.45,–0.87,–1.42 bar) for 15 d and relative growth rate (RGR), percent tissue water content (% TWC), osmolytes (proline–Pro, glycine betaine—GB, total soluble sugars—TSS) accumulation, malondialehyde (MDA) content as well as antioxidant enzyme activities such as superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) were analysed. Our findings showed that RGR and percent TWC was decreased significantly with the intensity of drought stress in both cultivars, but the RGR reduction was least (five folds) in cv. IGPN 2004 than in cv. GA 10 (6.2 folds). In osmolyte accumulation such as Pro and GB, cv. IGPN 2004 was found superior (5.5 and ten folds higher, respectively) to tolerate drought stress than GA 10; however, no change was observed in TSS accumulation. Further, it was noted that cv. IGPN 2004 caused least oxidative damage to the membranes. It also exhibited better SOD, CAT and APX activities and had higher α-tocopherol content. The least reduction in growth and MDA content and higher osmolytes and antioxidant activities in cv. IGPN 2004 revealed more drought stress tolerance at cellular level. It was suggested that increased drought tolerance of cv. IGPN 2004 was coupled with its better maintenance of RGR, percent TWC, reduced lipid peroxidation, more accumulation of osmolytes and higher antioxidant enzymes.

The present study deals with the growth, photosynthesis, oxidative stress and heavy metal accumulation ability of Nostoc muscorum exposed to different levels (2, 4, 8, 16, 20 μM) of cadmium (Cd) concentrations. Growth and photosynthetic pigments i.e., chlorophyll a, carotenoids and phycocyanin were significantly affected by cadmium exposure and inhibition was found to be dose dependent. ¹⁴C-fixation appeared to be more sensitive to Cd than whole cell oxygen evolution. Significant accumulation of Cd in the cells of N. muscorum was noticed after 1 and 2 h of exposure and the accumulation rate was dose and time dependent. Furthermore, the levels of superoxide radicals and hydrogen peroxide (H₂O₂) were found significantly increased by cadmium exposure which in turn accelerated the formation of malondialdehyde (MDA) content, and protein and DNA damage. The selected dose of Cd (20 μM) showed the induction of new polypeptide of ~23.24 kD and the loss of ~37.84 kD and ~69.63 kD whereas the remaining bands were inhibited as compared to control. Significant DNA fragmentation which is a hallmark of programmed cell death (PCD) was also observed in the cells treated with 20 μM of Cd for 48 h. The decrease in proline and total phenol content at 8 and 16 μM suggest that the cells of N. muscorum were not able to mitigate the oxidative stress induced by cadmium exposure. Similarly, the decreased activities of antioxidant enzymes i.e., superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) also indicates the failure of the antioxidant defense system of N. muscorum to survive at higher concentration (8 and 16 μM) of cadmium.

The facts of both positive and negative influences of cytokinins on stress resistance of plants are known today. Without pretending to a final choice between these points of view, we have made an attempt to analyze the details of the experiments that gave rise to conclusions about the nature of the effect of cytokinins on the resistance to stress-causing influences with a focus on their intensity and duration. The review deals with the data concerning the influence of different adverse factors on the content of endogenous cytokinins and transduction of cytokinin signals, examines the influence on plant resistance of treatment with exogenous hormone, and the effects of genetic modifications causing changes in cytokinin content and signaling. Resistance is considered not only as a mean of plant survival under severe stress but also as an instrument of maintaining growth rate in plants exposed to moderate stress. Literature data and our own results make it possible to conclude that cytokinins play an important role in formation of plant resistance to adverse influences; however, the effect of these hormones depends on stress intensity. Under moderate stress, cytokinins ensure maintenance of plant growth, whereas a drop in cytokinins hampers growth under a strong influence of adverse factors, which is a prerequisite for mobilization of limited resources characteristic of severe stress and ensures preservation of plant viability.