Dependence of root biomass accumulation on the content and metabolism of cytokinins in ethylene-insensitive plants

Diverse functions of ethylene in plants may depend on its ability to interact with other hormones. We studied the participation of ethylene in the regulation of accumulation and metabolism of cytokinins comparing ethylene-insensitive mutant plants of arabidopsis (Arabidopsis thaliana [L.] Heynh., etr1-1) with the plants of original ecotype Columbia (Col-0). Because cytokinins can regulate growth of both leaves and roots, we determined the weights of these organs and the ratio between them. The content of zeatin and its riboside in the roots of etr1-1 plants was two times greater than in Col-0 plants, which could be accounted for by inhibition of conversion of these forms of cytokinins into 9-N-glucosides. In the leaves of mutant plants, expression of IPT3 gene responsible for the synthesis of cytokinins was more intense than in Col-0 plants, which could also contribute to a rise in the content of cytokinins. In this case, the weight of roots in etr1-1 mutants was lower than in the plants of original ecotype. Because high concentrations of cytokinins can inhibit root growth, suppression of accumulation of their biomass in mutant plants may be related to a greater content of cytokinins therein. The obtained results suggest that ethylene can suppress accumulation of cytokinins and, thereby, maintain redistribution of biomass in favor of the roots, which is important for plant adaptation to a shortage of water and ions.     

Immunohistological localization and quantification of IAA in studies of root growth regulation

The content and distribution of auxins were studied in gravistimulated roots of maize (Zea mays L.) and primary roots of 7-day-old wheat (Triticum durum Desf.) seedlings, which branching was enhanced by excision of adventitious roots. IAA localization was observed immunohistochemically, using specific anti-IAA antibody in combination with second (anti-species) antibody labeled with colloidal gold. Differences in the IAA content (staining intensity) were found between upper and lower parts of gravistimulated maize roots. We also observed IAA accumulation in the primary wheat root after adventitious root excision; the cells of lateral root primordia were characterized by more intense IAA staining. The role of auxin redistribution in plants for lateral root initiation and development is discussed.     

Role of auxins and cytokinins in the development of lateral roots in wheat plants with several roots removed

The removal of four of five roots of 7–8-day-old wheat plants resulted in the activation of lateral root growth and the initiation of lateral root primordia on the remained root as compared to the main root of intact plants. The extent of this growth response depended on placing cut surface above or beneath the surface of the nutrient solution. The measurement of the IAA and cytokinin contents showed accumulation of these hormones in the root of experimental plants as compared to the main root of intact plants. IAA accumulation was correlated with the number of lateral roots and their primordia. The analysis of hormonal balance and their transport from the shoot to the root permits discussing the involvement of these hormones and their interaction in the control of root growth at the stages of both primordium initiation and development and lateral root elongation.     

Characterization of the Novel Plant Growth-Stimulating Strain Advenella kashmirensis IB-K1 and Evaluation of Its Efficiency in Saline Soil

Microbiology - The strain of facultative chemolithotrophic bacteria isolated from soil within the aphotic zone of the Kinderlinskaya Cave (Southern Urals, Russia) was identified as member of the...     

The role of curcumin on intestinal oxidative stress,cell proliferation and apoptosis after ischemia/reperfusion injury in rats

The aim of this study was to demonstrate the role of curcumin on oxidative stress, cell proliferation and apoptosis in the rat intestinal mucosa after ischemia/reperfusion (I/R). A total of 30 male Wistar albino rats were divided into three groups: sham, I/R and I/R+ curcumin; each group contain 10 animals. Sham group animals underwent laparotomy without I/R injury. After I/R groups animals underwent laparotomy, 1 h of superior mesenteric artery ligation were followed by 1 h of reperfusion. In the curcumin group, 3 days before I/R, curcumin (100 mg/kg) was administered by gastric gavage. All animals were sacrificed at the end of reperfusion and intestinal tissues samples were obtained for biochemical and histopathological investigation in all groups. Curcumin treatment significantly decreased the elevated tissue malondialdehyde levels and increased of reduced superoxide dismutase, and glutathione peroxidase enzyme activities in intestinal tissues samples. I/R caused severe histopathological injury including mucosal erosions and villous congestion and hemorrhage. Curcumin treatment significantly attenuated the severity of intestinal I/R injury, with inhibiting of I/R-induced apoptosis and cell proliferation. These results suggest that curcumin treatment has a protective effect against intestinal damage induced by intestinal I/R. This protective effect is possibly due to its ability to inhibit I/R-induced oxidative stress, apoptosis and cell proliferation.     

Lymphocyte DNA damage in patients with acute coronary syndrome and its relationship with severity of acute coronary syndrome

OBJECTIVE: The aim of this study was to investigate the association between lymphocyte DNA damage and acute coronary syndromes (ACS). METHODS: The study population contained 53 patients with ACS, 48 patients with stable angina and 35 voluntary healty subjects. DNA damage was assessed by alkaline comed assay in peripheral lymphocyte and plasma levels of total antioxidant capacity (TAC) were determined using a novel automated measurement method. RESULTS: In ACS patients, DNA damage was significantly higher than in patients with stable angina and control subjects (144+/-52 AU, 116+/-37, 68+/-34 AU; for three p<0.001, respectively). The TAC levels in patients with ACS were lower than the other groups (1.24+/-0.31 mmol Trolox equiv./l, 1.46+/-0.29 mmol Trolox equiv./l, p<0.05, respectively). DNA damage values in patients with acute miyocardial infarction were significantly higher than in patients with unstable angina (159.8+/-53.0 AU versus 131.8+/-48.4 AU; p<0.05, respectively). Lymphocyte DNA damage values in patients with ACS showed positive correlation with d-dimer (r=0.880, p<0.001) troponin I (r=538, p<0.001) and C-reactive protein (r=0.544, p<0.001) and negative correlation with TAC (r=-0.346, p=0.011). In multiple linear regression analysis, TAC (beta=-0.213, p=0.001) and d-dimer (beta=0.697, p<0.001) were independent predictors of DNA damage in patients with ACS. CONCLUSIONS:These findings indicate that lymphocyte DNA damage level increases in patients with ACS. Elevated DNA damage may be related with plaque instability and be useful for the identification of patients with acute coronary syndromes.     

Ability of bacterium Bacillus subtilis to produce cytokinins and to influence the growth and endogenous hormone content of lettuce plants

Hormone production by micro-organisms selected as antagonists of pathogenic fungi and the effect of their introduction into soil on hormone content and growth of lettuce plants were studied. Hormones in bacterial cultural media and in plant extracts were immunopurified and assayed using specific antibodies to indolyl-3-acetic acid (IAA), abscisic acid (ABA), and different cytokinins (zeatin riboside (ZR), dihydrozeatinriboside (DHZR) and isopentenyladenosine (iPA)). ZR was shown to be the main cytokinin present in bacterial cultural media as a complex with a high molecular weight component. Inoculation of lettuce plants with bacteria increased the cytokinin content of both shoots and roots. Accumulation of zeatin and its riboside was greatest in roots shortly 2days after inoculation, when their content was 10 times higher than in control. Changes in the content of other hormones (ABA and IAA) were observed at the end of experiments only. Accumulation of cytokinins in inoculated lettuce plants was associated with an increase in plant shoot and root weight of approximately 30% over 8days.     

Rapid and tissue-specific changes in ABA and in growth rate in response to salinity in barley leaves

The addition of 100 mM NaCl to the root medium of barley plantscaused the rapid cessation of elongation of the growing leafthree, followed by a sudden resumption of growth during thefollowing hour. The idea that resumption of growth is precededand mediated by rapid and tissue-specific changes in ABA concentrationand by changes in transpiration was tested. Leaf elongationvelocity was recorded continuously using linear variable displacementtransducers (LVDT), ABA was determined by immunoassay, and transpirationand stomatal conductivity were measured gravimetrically andby porometry, respectively. Within 10 min following additionof salt, ABA increased 6-fold in the distal portion of the leafelongation zone; in the proximal portion, ABA accumulated witha delay. In the portion of the growing blade that had emergedABA increased 3-fold and remained elevated during the following20 min. This preceded a decrease in transpiration and stomatalconductivity, which, in turn, coincided with growth resumption.Twenty hours following the addition of salt, the ABA concentrationshad returned to the level before stress. Leaf elongation velocitywas still reduced. It is concluded that NaCl causes a rapidincrease in ABA in the transpiring portion of the growing leaf.This leads to a decrease in transpiration. As a result, xylemwater potential is expected to rise. The moment that the waterpotential gradient between the xylem and the peripheral cellsin the growth zone favours water uptake again into the latter,leaf elongation resumes. The results suggest that ABA causesdifferent responses in different leaf regions, all aimed atpromoting the resumption of leaf growth. Key words: Abscisic acid, cell elongation, Hordeum vulgare, leaf growth, salinity, water relations.