Calcium-Promoted Interaction between the C2-Domain Protein EHB1 and Metal Transporter IRT1 Inhibits Arabidopsis Iron Acquisition.

Iron is a key transition element in the biosphere and is crucial for living organisms, although its cellular excess can be deleterious. Maintaining the balance of optimal iron availability in the model plant Arabidopsis (Arabidopsis thaliana) requires the precise operation of iron import through the principal iron transporter IRON-REGULATED TRANSPORTER1 (IRT1). Targeted inhibition of IRT1 can prevent oxidative stress, thus promoting plant survival. Here, we report the identification of an IRT1 inhibitor, namely the C2 domain-containing peripheral membrane protein ENHANCED BENDING1 (EHB1). EHB1 interacts with the cytoplasmically exposed variable region of IRT1, and we demonstrate that this interaction is greatly promoted by the presence of calcium. We found that EHB1 binds lipids characteristic of the plasma membrane, and the interaction between EHB1 and plant membranes is calcium-dependent. Molecular simulations showed that EHB1 membrane binding is a two-step process that precedes the interaction between EHB1 and IRT1. Genetic and physiological analyses indicated that EHB1 acts as a negative regulator of iron acquisition. The presence of EHB1 prevented the IRT1-mediated complementation of iron-deficient fet3fet4 yeast (Saccharomyces cerevisiae). Our data suggest that EHB1 acts as a direct inhibitor of IRT1-mediated iron import into the cell. These findings represent a major step in understanding plant iron acquisition, a process that underlies the primary production of bioavailable iron for land ecosystems.

Natural selenium particles from Staphylococcus carnosus: Hazards or particles with particular promise?

Various bacteria, including diverse Staphylococci, reduce selenite to yield red selenium particles with diameters in the high nanometer to low micrometer range. Formation and accumulation of such particles in bacteria often results in cell death, triggered by a loss of thiols and formation of disruptive deposits inside the cell. Hence certain pathogenic bacteria are rather sensitive to the presence of selenite, whilst other organisms, such as small nematodes, do not employ this kind of nanotechnology, yet become affected by micromolar concentrations of such naturally generated materials. Selenium particles extracted from cultures of Staphylococcus carnosus and apparently stabilized by their natural protein coating, for instance, show considerable activity against the nematode Steinernema feltiae, Escherichia coli and Saccaromyces cerevisiae. Such natural nano- and micro-particles are also more active than mechanically generated selenium particles and may be applied as antimicrobial materials in Medicine and Agriculture.

Turning Waste into Value: Nanosized Natural Plant Materials of Solanum incanum L. and Pterocarpus erinaceus Poir with Promising Antimicrobial Activities.

Numerous plants are known to exhibit considerable biological activities in the fields of medicine and agriculture, yet access to their active ingredients is often complicated, cumbersome and expensive. As a consequence, many plants harbouring potential drugs or green phyto-protectants go largely unnoticed, especially in poorer countries which, at the same time, are in desperate need of antimicrobial agents. As in the case of plants such as the Jericho tomato, Solanum incanum, and the common African tree Pterocarpus erinaceus, nanosizing of original plant materials may provide an interesting alternative to extensive extraction and isolation procedures. Indeed, it is straightforward to obtain considerable amounts of such common, often weed-like plants, and to mill the dried material to more or less uniform particles of microscopic and nanoscopic size. These particles exhibit activity against Steinernema feltiae or Escherichia coli, which is comparable to the ones seen for processed extracts of the same, respective plants. As S. feltiae is used as a model nematode indicative of possible phyto-protective uses in the agricultural arena, these findings also showcase the potential of nanosizing of crude "waste" plant materials for specific practical applications, especially-but not exclusively-in developing countries lacking a more sophisticated industrial infrastructure.