University of Zagreb

About: University of Zagreb is a education organization based out in Zagreb, Grad Zagreb, Croatia. It is known for research contribution in the topics: Population & European union. The organization has 21769 authors who have published 50267 publications receiving 783239 citations. The organization is also known as: Zagreb University & Sveučilište u Zagrebu.

Glucosinolates and their potential role in plant

Abstract: Glucosinolates are sulfur- and nitrogen-containing plant secondary metabolites common in the Brassicaceae and related plant families. In the plant, they coexist with an endogenous ?-thioglucosidase (EC 3.2.3.1) called myrosinase, though glucosinolates are stored in the vacuoles of so-called S-cells and myrosinase in separate but adjacent cells. Upon plant tissue disruption, glucosinolates are released at the damage site and become hydrolyzed by myrosinase. The chemical nature of the hydrolysis products depends on the structure of the glucosinolate side chain, plant species and reaction conditions. Biosynthesis of glucosinolates comprises three phases: (i) amino acid chain elongation, in which additional methylene groups are inserted into the side chain, (ii) conversion of the amino acid moiety to the glucosinolate core structure, (iii) and subsequent side chain modifications. Glucosinolate pattern differs between species and ecotype as well as between and even within individual plants, depending on developmental stage, tissue and photoperiod. A number of environmental conditions such as light plant, nutritional status, fungal infection, wounding and insect damage can alter the glucosinolate pattern significantly. The change of the glucosinolate profile by several environmental factors has brought forward different theories regarding their potential roles in the plant. However, the most accepted theory is that the glucosinolate-myrosinase system is involved in defense against herbivores and pathogens. This review summarized recent progress in glucosinolate biosynthesis, degradation and organization of the myrosinase-glucosinolate system. Furthermore, current knowledge of the potential role of glucosinolates in the plant, especially in plant defense, is discussed.

The Effects of Cadmium-Zinc Interactions on Biochemical Responses in Tobacco Seedlings and Adult Plants

Abstract: The objective of the present study was to investigate the effects of cadmium-zinc (Cd-Zn) interactions on their uptake, oxidative damage of cell macromolecules (lipids, proteins, DNA) and activities of antioxidative enzymes in tobacco seedlings as well as roots and leaves of adult plants. Seedlings and plants were exposed to Cd (10 µM and 15 µM) and Zn (25 µM and 50 µM) as well as their combinations (10 µM or 15 µM Cd with either 25 µM or 50 µM Zn). Measurement of metal accumulation exhibited that Zn had mostly positive effect on Cd uptake in roots and seedlings, while Cd had antagonistic effect on Zn uptake in leaves and roots. According to examined oxidative stress parameters, in seedlings and roots individual Cd treatments induced oxidative damage, which was less prominent in combined treatments, indicating that the presence of Zn alleviates oxidative stress. However, DNA damage found in seedlings, and lower glutathione reductase (GR) and superoxide dismutase (SOD) activity recorded in both seedlings and roots, after individual Zn treatments, indicate that Zn accumulation could impose toxic effects. In leaves, oxidative stress was found after exposure to Cd either alone or in combination with Zn, thus implying that in this tissue Zn did not have alleviating effects. In conclusion, results obtained in different tobacco tissues suggest tissue-dependent Cd-Zn interactions, which resulted in activation of different mechanisms involved in the protection against metal stress.

Composite conversion and temperature rise using a conventional, plasma arc, and an experimental blue LED curing unit

Abstract: The objective of this study was to evaluate the degree of conversion and temperature rise in three different composite materials when illuminated by an experimental light source [blue superbright light emitting diodes (LEDs)] and compared with plasma light and traditional photopolymerization unit. The degree of conversion and temperature rise were measured using Fourier transform infrared (FTIR) spectroscopy and digital multimeter, respectively. The results revealed significantly higher degree of conversion values in case of conventional curing than with other two light sources whereas temperature rise was significantly lower when blue LEDs and plasma light were used. There were great differences in light intensities between blue LEDs of only 9 mW cm-2 compared with plasma light of 1370 mW cm-2 and Elipar II of 560 mW cm-2. Better match of LED spectral distribution peak to camphorquinone absorption distribution peak probably explains much lower intensities used for similar photopolymerization effect like in the case of rapid plasma lamp curing.

Effects of radiofrequency electromagnetic fields on seed germination and root meristematic cells of Allium cepa L.

Abstract: The effects of exposure to radiofrequency electromagnetic fields (RF-EMFs) on seed germination, primary root growth as well as mitotic activity and mitotic aberrations in root meristematic cells were examined in Allium cepa L. cv. Srebrnjak Majski. Seeds were exposed for 2h to EMFs of 400 and 900MHz at field strengths of 10, 23, 41 and 120Vm(-1). The effect of longer exposure time (4h) and field modulation was investigated at 23Vm(-1) as well. Germination rate and root length did not change significantly after exposure to radiofrequency fields under any of the treatment conditions. At 900MHz, exposures to EMFs of higher field strengths (41 and 120Vm(-1)) or to modulated fields showed a significant increase of the mitotic index compared with corresponding controls, while the percentage of mitotic abnormalities increased after all exposure treatments. On the other hand, at 400MHz the mitotic index increased only after exposure to modulated EMF. At this frequency, compared with the control higher numbers of mitotic abnormalities were found after exposure to modulated EMF as well as after exposure to EMFs of higher strengths (41 and 120Vm(-1)). The types of aberration induced by the EMFs of both frequencies were quite similar, mainly consisting of lagging chromosomes, vagrants, disturbed anaphases and chromosome stickiness. Our results show that non-thermal exposure to the radiofrequency fields investigated here can induce mitotic aberrations in root meristematic cells of A. cepa. The observed effects were markedly dependent on the field frequencies applied as well as on field strength and modulation. Our findings also indicate that mitotic effects of RF-EMF could be due to impairment of the mitotic spindle.

Enzymes of the shikimic acid pathway encoded in the genome of a basal metazoan, Nematostella vectensis, have microbial origins

Abstract: The shikimic acid pathway is responsible for the biosynthesis of many aromatic compounds by a broad range of organisms, including bacteria, fungi, plants, and some protozoans. Animals are considered to lack this pathway, as evinced by their dietary requirement for shikimate-derived aromatic amino acids. We challenge the universality of this traditional view in this report of genes encoding enzymes for the shikimate pathway in an animal, the starlet sea anemone Nematostella vectensis. Molecular evidence establishes horizontal transfer of ancestral genes of the shikimic acid pathway into the N. vectensis genome from both bacterial and eukaryotic (dinoflagellate) donors. Bioinformatic analysis also reveals four genes that are closely related to those of Tenacibaculum sp. MED152, raising speculation for the existence of a previously unsuspected bacterial symbiont. Indeed, the genome of the holobiont (i.e., the entity consisting of the host and its symbionts) comprises a high content of Tenacibaculum-like gene orthologs, including a 16S rRNA sequence that establishes the phylogenetic position of this associate to be within the family Flavobacteriaceae. These results provide a complementary view for the biogenesis of shikimate-related metabolites in marine Cnidaria as a “shared metabolic adaptation” between the partners.