Some aspects of the iodine metabolism of the giant kelp Macrocystis pyrifera (phaeophyceae)

Ocean acidification significantly alters the trace element content of the kelp, Saccharina latissima

Seaweeds are ecosystem engineers that can serve as habitat, sequester carbon, buffer ecosystems against acidification, and, in an aquaculture setting, represent an important food source. One health issue regarding the consumption of seaweeds and specifically, kelp, is the accumulation of some trace elements of concern within tissues. As atmospheric CO2 concentrations rise, and global oceans acidify, the concentrations of elements in seawater and kelp may change. Here, we cultivated the sugar kelp, Saccharina latissima under ambient (~400 μatm) and elevated pCO2 (600-2400 μatm) conditions and examined the accumulation of trace elements using x-ray powder diffraction, sub-micron resolution x-ray imaging, and inductively coupled plasma mass spectrometry. Exposure of S. latissima to higher concentrations of pCO2 and lower pH caused a significant increase (p < 0.05) in the iodine and arsenic content of kelp along with increased subcellular heterogeneity of these two elements as well as bromine. The iodine-to‑calcium and bromine-to‑calcium ratios of kelp also increased significantly under high CO2/low pH (p < 0.05). In contrast, high CO2/low pH significantly reduced levels of copper and cadmium in kelp tissue (p < 0.05) and there were significant inverse correlations between concentrations of pCO2 and concentrations of cadmium and copper in kelp (p < 0.05). Changes in copper and cadmium levels in kelp were counter to expected changes in their free ionic concentrations in seawater, suggesting that the influence of low pH on algal physiology was an important control on the elemental content of kelp. Collectively, these findings reveal the complex effects of ocean acidification on the elemental composition of seaweeds and indicate that the elemental content of seaweeds used as food must be carefully monitored as climate change accelerates this century.

Discovery of Novel Pentacyclic Triterpene Acid Amide Derivatives as Excellent Antimicrobial Agents Dependent on Generation of Reactive Oxygen Species

Developing new agricultural bactericides is a feasible strategy for stopping the increase in the resistance of plant pathogenic bacteria. Some pentacyclic triterpene acid derivatives were elaborately designed and synthesized. In particular, compound A₂₂ exhibited the best antimicrobial activity against Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas axonopodis pv. citri (Xac) with EC₅₀ values of 3.34 and 3.30 mg L^-1, respectively. The antimicrobial mechanism showed that the compound A₂₂ induced excessive production and accumulation of reactive oxygen species (ROS) in Xoo cells, leading to a decrease in superoxide dismutase and catalase enzyme activities and an increase in malondialdehyde content. A₂₂ also produced increases in Xoo cell membrane permeability and eventual cell death. In addition, in vivo experiments showed that A₂₂ at 200 mg L^-1 exhibited protective activity against rice bacterial blight (50.44%) and citrus canker disease (84.37%). Therefore, this study provides a paradigm for the agricultural application of pentacyclic triterpene acid.

Synthesis of Organic Iodine Compounds in Sweetcorn under the Influence of Exogenous Foliar Application of Iodine and Vanadium

A human’s diet should be diverse and rich in vitamins, macro- and microelements essential for the proper functioning of the human body. Globally, a high percentage of the human population suffers from malnutrition, deficiencies of nutrients and vitamins also known as the problem of hidden hunger. This problem it is not only common in poor countries, but also occurs in developed countries. Iodine is a nutrient crucial for the proper functioning of the human and animal body. For plants, it is referred to as a beneficial element or even a microelement. The design of the biofortification experiment was determined on the basis of the interaction of iodine and vanadium (synergistic interaction in marine algae), where vanadium-dependent iodoperoxidase catalyzes apoplastic oxidation of iodine, resulting in high efficiency of iodine uptake and accumulation in brown algae (Laminaria digitate). Three independent experiments (Exp.) were carried out with the foliar application of vanadium (V) and iodine (I) compounds. The main differences between the experiments with the adapted proper corn biofortification method were the different application stage between the individual experiments, the application intervals and the dose of the iodine–vanadium compound. In each experiment, the accumulation of iodine and vanadium in the grain was several times lower than in the leaves. The combination iodine and vanadium significantly increased the accumulation of iodine in the grain in the case of applying V with inorganic iodine compounds, and a decrease in the accumulation of I after applying V with organic iodine compound —especially in Exp. No. 3. In grain, the highest content of I−, IO3− was in combination with the application of 2-iodobenzoic acid (products of its metabolism). In most of the tested combinations, vanadium stimulated the accumulation/synthesis of exogenous/endogenous 5-iodosalicylic acid (5ISA) and 2-iodobenzoic acid (2IBeA), respectively, and decreased the content of 2,3,5-triiodobenzoic acid (2,3,5-triIBeA) in leaves and grains. The tested compounds I and V and the combinations of their application had a diversified effect on the vitamin C content in the grains. Vanadium in the lower dose of 0.1 µM significantly increased the sugar content in the grain.

Key aspects of the iodine metabolism in brown algae: a brief critical review

Brown algae include the strongest accumulators of iodine known among living systems. This paper reviews the current state of bioinorganic research in the field, focusing on the models Laminaria digitata, Macrocystis pyrifera and Ectocarpus siliculosus, and covering uptake and efflux, localization and biological significance of storage, as well as marine and atmospheric chemistry of iodine.

Emission of volatile halogenated compounds, speciation and localization of bromine and iodine in the brown algal genome model Ectocarpus siliculosus

This study explores key features of bromine and iodine metabolism in the filamentous brown alga and genomics model Ectocarpus siliculosus. Both elements are accumulated in Ectocarpus, albeit at much lower concentration factors (2-3 orders of magnitude for iodine, and < 1 order of magnitude for bromine) than e.g. in the kelp Laminaria digitata. Iodide competitively reduces the accumulation of bromide. Both iodide and bromide are accumulated in the cell wall (apoplast) of Ectocarpus, with minor amounts of bromine also detectable in the cytosol. Ectocarpus emits a range of volatile halogenated compounds, the most prominent of which by far is methyl iodide. Interestingly, biosynthesis of this compound cannot be accounted for by vanadium haloperoxidase since the latter have not been found to catalyze direct halogenation of an unactivated methyl group or hydrocarbon so a methyl halide transferase-type production mechanism is proposed.

The potential role of kelp forests on iodine speciation in coastal seawater

Kelps have a major role in marine and atmospheric iodine cycling in the coastal zone of temperate regions, with potential wide-ranging impacts on ozone destruction in the coastal marine boundary layer. However, little is known about the impact of kelp forests on iodine speciation in coastal sea water. To address this, we examined iodide and iodate concentrations in seawater in and around a giant kelp forest near San Diego, CA, USA, and a nearby site that was not influenced by kelp biology. Our data shows that while both iodide and iodate concentrations remained unchanged during the year at the nearby site, these concentrations changed significantly in and around the kelp forest, and were strongly related to changes in kelp canopy biomass. In particular, iodide reached its highest concentration and iodate reached its lowest concentration during the summer when the kelp canopies were near their maximum, while the opposite pattern was observed during the winter and spring when the kelp canopies were near their minimum. Further, comparisons of these changes with corresponding changes in seawater temperature and wind speed indicated that these relationships were relatively small compared to those with changes in kelp biomass. Together, our data show a strong relationship between kelp biomass and iodine metabolism.