Nest covering in plovers: How modifying the visual environment influences egg camouflage

Camouflage is one of the most widespread antipredator defences, and its mechanistic basis has attracted considerable interest in recent years. The effectiveness of camouflage depends on the interaction between an animal's appearance and its background. Concealment can therefore be improved by changes to an animal's own appearance, by behaviorally selecting an optimal background, or by modifying the background to better match the animal's own appearance. Research to date has largely focussed on the first of these mechanisms, whereas there has been little work on the second and almost none on the third. Even though a number of animal species may potentially modify their environment to improve individual‐specific camouflage, this has rarely if ever been quantitatively investigated, or its adaptive value tested. Kittlitz's plovers (Charadrius pecuarius) use material (stones and vegetation) to cover their nests when predators approach, providing concealment that is independent of the inflexible appearance of the adult or eggs, and that can be adjusted to suit the local surrounding background. We used digital imaging and predator vision modeling to investigate the camouflage properties of covered nests, and whether their camouflage affected their survival. The plovers' nest‐covering materials were consistent with a trade‐off between selecting materials that matched the color of the eggs, while resulting in poorer nest pattern and contrast matching to the nest surroundings. Alternatively, the systematic use of materials with high‐contrast and small‐pattern grain sizes could reflect a deliberate disruptive coloration strategy, whereby high‐contrast material breaks up the telltale outline of the clutch. No camouflage variables predicted nest survival. Our study highlights the potential for camouflage to be enhanced by background modification. This provides a flexible system for modifying an animal's conspicuousness, to which the main limitation may be the available materials rather than the animal's appearance.     

Proteomic analysis of Medicago truncatula root plastids

Despite the recognized importance of non‐photosynthetic plastids in a wide array of plant processes, the root plastid proteome of soil‐grown plants still remains to be explored. In this study, we used a protocol allowing the isolation of Medicago truncatula root plastids with sufficient protein recovery and purity for their subsequent in‐depth analysis by nanoscale capillary LC‐MS/MS. Besides providing the first picture of a root plastid proteome, the results obtained highlighted the identification of 266 protein candidates whose functional distribution mainly resembled that of wheat endosperm amyloplasts and tobacco proplastids together with displaying major differences to those reported for chloroplasts. Most of the identified proteins have a role in nucleic acid‐related processes (16%), carbohydrate (15%) and nitrogen/sulphur (12%) metabolisms together with stress response mechanisms (10%). It is noteworthy that BLAST searches performed against the proteins reported in different plastidomes allowed detecting 30 putative root plastid proteins for which homologues were previously unsuspected as plastid‐located, most of them displaying a common putative role in participating in the plant cell responses against abiotic and/or biotic stresses. Taken together, the data obtained provide new insights into the functioning of root plastids and reinforce the emerging idea for an important role of these organelles in sustaining plant defence reactions.     

High-level production of poly (β-<Emphasis Type="SmallCaps">l</Emphasis>-malic acid) with a new isolated <Emphasis Type="Italic">Aureobasidium pullulans</Emphasis> strain

Poly (β-l-malic acid) (PMLA) is a water-soluble polyester with many attractive properties in chemical industry and medicine development. However, the low titer of PMLA in the available producer strains limits further industrialization efforts and restricts its many potential applications. In order to solve this problem, a new strain with the distinguished high productivity of PMLA was isolated from fresh plants samples. It was characterized as the candidate of Aureobasidium pullulans based on the morphology and phylogenetic analyses of the internal transcribed spacer sequences. After the optimization of culture conditions, the highest PMLA concentration (62.27 g l⁻¹) could be achieved in the shake flask scale. In addition, the contribution of the carbon flux to exopolysaccharide (EPS) and PMLA could be regulated by the addition of CaCO₃ in the medium. This high-level fermentation process was further scaled up in the 10 l benchtop fermentor with a high PMLA concentration (57.2 g l⁻¹) and productivity (0.35 g l⁻¹ h⁻¹), which are the highest level in all the literature. Finally, the suitable acid hydrolysis conditions of PMLA were also investigated with regard to the production of l-malic acid, and the kinetics of PMLA acid hydrolysis was modeled to simulate the whole degradation process. The present work paved the road to produce this multifunctional biomaterial (PMLA) at industrial scale and promised one alternative method to produce l-malic acid in the future.     

Exposure of colonic epithelial cells to oxidative and endoplasmic reticulum stress causes rapid potassium efflux and calcium influx

Endoplasmic reticulum (ER) stress and oxidative stress have recently been linked to the pathogenesis of inflammatory bowel diseases. Under physiological conditions, intestinal epithelial cells are exposed to ER and oxidative stress affecting the cellular ionic homeostasis. However, these altered ion flux ‘signatures’ during these stress conditions are poorly characterized. We investigated the kinetics of K⁺, Ca²⁺ and H⁺ ion fluxes during ER and oxidative stress in a colonic epithelial cell line LS174T using a non‐invasive microelectrode ion flux estimation technique. ER and oxidative stress were induced by cell exposure to tunicamycin (TM) and copper ascorbate (CuAsc), respectively, from 1 to 24 h. Dramatic K⁺ efflux was observed following acute ER stress with peak K⁺ efflux being ?30·6 and ?138·7 nmolm^?2 s^?1 for 10 and 50 µg ml^?1, respectively (p < 0·01). TM‐dependent Ca²⁺ uptake was more prolonged with peak values of 0·85 and 2·68 nmol m^?2 s^?1 for 10 and 50 µg ml^?1 TM, respectively (p < 0·02). Ion homeostasis was also affected by the duration of ER stress. Increased duration of TM treatment from 0 to 18 h led to increases in both K⁺ efflux and Ca²⁺ uptake. While K⁺ changes were significantly higher at each time point tested, Ca²⁺ uptake was significantly higher only after prolonged treatment (18 h). CuAsc also led to an increased K⁺ efflux and Ca²⁺ uptake. Functional assays to investigate the effect of inhibiting K⁺ efflux with tetraethylammonium resulted in increased cell viability. We conclude that ER/oxidative stress in colonic epithelial cells cause dramatic K⁺, Ca²⁺ and H⁺ ion flux changes, which may predispose this lineage to poor stress recovery reminiscent of that seen in inflammatory bowel diseases. Copyright © 2012 John Wiley & Sons, Ltd.