Silicon Differently Affects Apoplastic Binding of Excess Boron in Wheat and Sunflower Leaves.

Monocots and dicots differ in their boron (B) requirement, but also in their capacity to accumulate silicon (Si). Although an ameliorative effect of Si on B toxicity has been reported in various crops, differences among monocots and dicots are not clear, in particular in light of their ability to retain B in the leaf apoplast. In hydroponic experiments under controlled conditions, we studied the role of Si in the compartmentation of B within the leaves of wheat (Triticum vulgare L.) as a model of a high-Si monocot and sunflower (Helianthus annuus L.) as a model of a low-Si dicot, with the focus on the leaf apoplast. The stable isotopes 10B and 11B were used to investigate the dynamics of cell wall B binding capacity. In both crops, the application of Si did not affect B concentration in the root, but significantly decreased the B concentration in the leaves. However, the application of Si differently influenced the binding capacity of the leaf apoplast for excess B in wheat and sunflower. In wheat, whose capacity to retain B in the leaf cell walls is lower than in sunflower, the continuous supply of Si is crucial for an enhancement of high B tolerance in the shoot. On the other hand, the supply of Si did not contribute significantly in the extension of the B binding sites in sunflower leaves.

The assessment of soil availability and wheat grain status of zinc and iron in Serbia: Implications for human nutrition.

The deficiency of zinc (Zn) and iron (Fe) is a global issue causing not only considerable yield losses of food crops but also serious health problems. We have analysed Zn and Fe concentrations in the grains of two bread wheat cultivars along native gradient of micronutrient availability throughout Serbia. Although only 13% of the soil samples were Zn deficient and none was Fe deficient, the levels of these micronutrients in grain were rather low (median values of 21 mg kg(-1) for Zn and 36 mg kg(-1) for Fe), and even less adequate in white flour. Moreover, excessive P fertilization of calcareous soils in the major wheat growing areas strongly correlated with lower grain concentration of Zn. Our results imply that a latent Zn deficiency in wheat grain poses a high risk for grain quality relevant to human health in Serbia, where wheat bread is a staple food.

Association of small, dense low-density lipoprotein cholesterol and galectin-3 in patients with chronic kidney disease.

BACKGROUND: Dyslipidemia is a common feature of chronic kidney disease (CKD). Although it has been observed that the pattern of lipid abnormalities can vary according to the stage of CKD, there is lack of data concerning the distribution of lipoprotein subclasses at various stages of the disease. In addition, association of proatherogenic small, dense low-density lipoprotein (sdLDL) subclasses with markers of inflammation, such is galectin-3, is not sufficiently explored. The aim of this study was to analyze concentrations and relative proportions of sdLDL-cholesterol (sdLDL-C) and galectin-3 in patients with CKD, with respect to the stage of the disease. Also, we sought possible independent associations of galectin-3 and sdLDL-C. METHODS: The study involved 100 hemodialysis (HD) and 50 pre-dialysis patients, together with 94 healthy individuals. SdLDL-C was measured by heparin-magnesium precipitation method. Galectin-3 was measured by ELISA technique. RESULTS: Galectin-3 levels were higher in pre-dialysis and HD patients than in the control group (p < 0.01). The concentration of sdLDL-C was highest in the pre-dialysis group and lowest in HD patients (p < 0.01). CKD patients with increased galectin-3 concentrations had significantly higher relative proportions of cholesterol in sdLDL (% sdLDL-C) than their counterparts with lower galectin-3 levels (p < 0.05). Relative proportion of sdLDL-C was shown to be an independent determinant of galectin-3 concentration. CONCLUSIONS: Our results demonstrated alterations in concentrations and proportions of sdLDL-C according to the stages of CKD. The observed independent associations of % sdLDL-C and galectin-3 provide further insight into their complex interaction during the progression of atherosclerosis in CKD.

Genetic and association mapping study of wheat agronomic traits under contrasting water regimes.

Genetic analyses and association mapping were performed on a winter wheat core collection of 96 accessions sampled from a variety of geographic origins. Twenty-four agronomic traits were evaluated over 3 years under fully irrigated, rainfed and drought treatments. Grain yield was the most sensitive trait to water deficit and was highly correlated with above-ground biomass per plant and number of kernels per m(2). The germplasm was structured into four subpopulations. The association of 46 SSR loci distributed throughout the wheat genome with yield and agronomic traits was analyzed using a general linear model, where subpopulation information was used to control false-positive or spurious marker-trait associations (MTAs). A total of 26, 21 and 29 significant (P < 0.001) MTAs were identified in irrigated, rainfed and drought treatments, respectively. The marker effects ranged from 14.0 to 50.8%. Combined across all treatments, 34 significant (P < 0.001) MTAs were identified with nine markers, and R(2) ranged from 14.5 to 50.2%. Marker psp3200 (6DS) and particularly gwm484 (2DS) were associated with many significant MTAs in each treatment and explained the greatest proportion of phenotypic variation. Although we were not able to recognize any marker related to grain yield under drought stress, a number of MTAs associated with developmental and agronomic traits highly correlated with grain yield under drought were identified.

Boron uptake by the root cortex symplast of tomato and pea plants: evidence for low-boron-induced active transport.

The objective of this research was to test the hypothesis of the existence of an active boron (B) uptake into the cortical cells induced by low B supply. The uptake of B was characterised in two tomato (Lycopersicon esculentum Mill.) genotypes: B-efficient FER and B-inefficient mutant T3238. In addition, pea (Pisum sativum L.) was used as an anatomically appropriate model for obtaining intact root cortex. Time course uptake studies in tomato indicate that the B-inefficient mutant was defective by the absence of an active low-B-induced uptake system in the cortex. Pea roots showed up to 10-fold higher accumulation of B into the cortex symplast at low (0.5 µm) external B supply in comparison to adequate B (10 µm) supply. Also, low-B-induced uptake of B was strongly inhibited by 2,4-dinitrophenol, indicating a metabolic energy-derived active component of B uptake at low external supply. Uptake of B by the cortical cells of tomato and pea plants appears to be a combination of both passive and active components, with a passive component prevailing at higher external B. An active component of B uptake suppressed by either adequate or high B supply might indicate a downregulation of plasma membrane-associated B transporter(s) in root cortical cells.