Variability in iodine in temperate seaweeds and iodine accumulation kinetics of Fucus vesiculosus and Laminaria digitata (Phaeophyceae,Ochrophyta)

The biogeochemistry of iodine in temperate coastal ecosystems is largely mediated by macroalgae, which act as a major biological sink and source of iodine. Their capacity to accumulate, retain and release iodine has been associated with abiotic and biotic stressors, but quantitative information is limited. We evaluated the seasonal iodine retention capacity of eleven macroalgal species belonging to different systematic groups, collected from two sites in Ireland. Iodine accumulation and retention were then further quantified in Fucus vesiculosus and Laminaria digitata in relation to I^? concentrations in seawater and temperature. In general, iodine contents were ~10¹–10² μmol · (g dw)^?1 for Laminariales, 10⁰–10¹ μmol · (g dw)^?1 for Fucales, 10^?1–10⁰ μmol · (g dw)^?1 for Rhodophyta, and 10^?1 μmol · (g dw)^?1 for Chlorophyta. Typically, algal iodine contents were above average in winter and below average in summer. Iodine accumulation in F. vesiculosus and L. digitata depended on I^? availability and followed the Michaelis‐Menten kinetic. The ratio of maximum accumulation rate to half accumulation coefficient (ρ_max: K _t) was 2.4 times higher for F. vesiculosus than for L. digitata , suggesting that F. vesiculosus was more efficient in iodine accumulation. Both species exhibited a temperature‐dependent net loss of iodine, and only an exposure to sufficient external I^? concentrations compensated for this loss. This study revealed that both environmental (e.g., I^? in seawater, temperature) and organismal (e.g., the status of the iodine storage pool) variables determine retention and variability in iodine in temperate seaweeds.     

Genome-wide analysis of the invertase gene family from maize

Key message

The recent release of the maize genome (AGPv4) contains annotation errors of invertase genes and therefore the enzymes are bestly curated manually at the protein level in a comprehensible fashion

Abstract

The synthesis, transport and degradation of sucrose are determining factors for biomass allocation and yield of crop plants. Invertase (INV) is a key enzyme of carbon metabolism in both source and sink tissues. Current releases of the maize genome correctly annotates only two vacuolar invertases (ivr1 and ivr2) and four cell wall invertases (incw1, incw2 (mn1), incw3, and incw4). Our comprehensive survey identified 21 INV isogenes for which we propose a standard nomenclature grouped phylogenetically by amino acid similarity: three vacuolar (INVVR), eight cell wall (INVCW), and ten alkaline/neutral (INVAN) isogenes which form separate dendogram branches due to distinct molecular features. The acidic enzymes were curated for the presence of the DPN tripeptide which is coded by one of the smallest exons reported in plants. Particular attention was placed on the molecular role of INV in vascular tissues such as the nodes, internodes, leaf sheath, husk leaves and roots. We report the expression profile of most members of the maize INV family in nine tissues in two developmental stages, R1 and R3. INVCW7, INVVR2, INVAN8, INVAN9, INVAN10, and INVAN3 displayed the highest absolute expressions in most tissues. INVVR3, INVCW5, INVCW8, and INVAN1 showed low mRNA levels. Expressions of most INVs were repressed from stage R1 to R3, except for INVCW7 which increased significantly in all tissues after flowering. The mRNA levels of INVCW7 in the vegetative stem correlated with a higher transport rate of assimilates from leaves to the cob which led to starch accumulation and growth of the female reproductive organs.

     

The inhibition of sphingomyelin synthase 1 activity induces collecting duct cells to lose their epithelial phenotype

Epithelial tissue requires that cells attach to each other and to the extracellular matrix by the assembly of adherens junctions (AJ) and focal adhesions (FA) respectively. We have previously shown that, in renal papillary collecting duct (CD) cells, both AJ and FA are located in sphingomyelin (SM)-enriched plasma membrane microdomains. In the present work, we investigated the involvement of SM metabolism in the preservation of the epithelial cell phenotype and tissue organization. To this end, primary cultures of renal papillary CD cells were performed. Cultured cells preserved the fully differentiated epithelial phenotype as reflected by the presence of primary cilia. Cells were then incubated for 24 h with increasing concentrations of D609, a SM synthase (SMS) inhibitor. Knock-down experiments silencing SMS 1 and 2 were also performed. By combining biochemical and immunofluorescence studies, we found experimental evidences suggesting that, in CD cells, SMS 1 activity is essential for the preservation of cell-cell adhesion structures and therefore for the maintenance of CD tissue/tubular organization. The inhibition of SMS 1 activity induced CD cells to lose their epithelial phenotype and to undergo an epithelial-mesenchymal transition (EMT) process.     

Seasonal changes in the prepuce of adult Fallow deer (Dama dama) and its probable function as a scent organ

The penis sheath of adult Fallow deer, which is an integral part of the abdominal skin, extends from the scrotum to the preputial orifice. Marked seasonal changes occur in the prepuce. In the non-rutting animal, the outer region of the prepuce, which is similar in structure to normal skin, passes through a transition zone characterized by a corrugated epidermis and multi-lobed sebaceous glands, before becoming the inner-sheath lining. Just before the rut, hypertrophy of the epidermis of the transition zone occurs with the formation of keratinous villi-like processes. The sebaceous glands enlarge and lipid production is increased. At the beginning of the rut, the transition zone everts and becomes located on the outer periphery of the prepuce, which now has the appearance of a dark brown, coarse, short-haired brush. At this stage, the animal and its voided urine develop a characteristic pungent odour whereas urine aspirated from the bladder is relatively odourless. After the rut, the prepuce returns to normal, the keratinous papillae being shed. It is suggested that the strong smelling rutting odour of male Fallow deer helps to synchronize oestrus in the females. The gross hyperkeratosis and associated epidermal hypertrophy of the prepuce produces a sponge-like mass which may help in scent production and dispersal.     

Triphenyltin as inductor of mitochondrial membrane permeability transition

The effect of triphenyltin on mitochondrial Ca²⁺ content was studied. It was found that this trialkyltin compound induces an increase in membrane permeability that leads to Ca²⁺ release, drop of the transmembrane potential, and efflux of matrix proteins. Interestingly, cyclosporin A was unable to inhibit triphenyltin-induced Ca²⁺ release. Based on these results it is proposed that the hyperpermeable state is produced by modification of 2.25 nmol of membrane thiol groups.     

Untersuchungen Zur Eosinophilie Hyalinen Knorpels

Zusammenfassung Während der chemischen Fixierung von Geweben und der nachfolgenden Behandlung in Alkoholreihen geht Hämoglobin in Lösung und diffundiert in das Gewebe. Die Diffusion des Hämoglobins ist besonders gut in der Grundsubstanz hyaliner Knorpel zu verfolgen. Das eingedrungene Hämoglobin wurde mit der Ultramikrospektrographie nachgewiesen. Die Hämoglobindiffusion läßt sich durch die Kryostatschnittechnik und durch eine Fixierung in 4%igem Formalin mit Zusatz von 2,5% Ferricyankalium verhindern bzw. mit Zusatz von Natriumchlorid oder Phosphat zu Formalin einschränken. Besonders säurehaltige Fixierungslösungen trennen die Häm- von der Globinkomponente. Der Globinanteil verbleibt in der Grundsubstanz des Knorpels und kann das Vorliegen eines ortsständigen Eiweiß-körpers vortäuschen. Die Einlagerung des vollständigen Hämoglobins oder des Globins allein bedingen die diffuse Eosinophilie der Grundsubstanz im fixierten Knorpel und blockiert die Darstellung der sauren Mucopolysaccharide (Alcianblaufärbung) sowie die metachromatische Reaktion der Grundsubstanz.

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Summary In the course of chemical fixation of tissues and the subsequent treatment with alcohol hemoglobin dissolves and diffuses into the tissue. The diffusion of hemoglobin can be observed particularly well in the ground substance of hyaline cartilage. There the hemoglobin is demonstrable by means of ultramicrospectrography. The diffusion of the hemoglobin can be prevented through the use of the cryostat technique and fixation in 4% formalin containing 2.5% ferricyankalium, NaCl or phosphate. Acid containing fixation media separate the hem from the globin component. The globin remains in the ground substance of the cartilage and may be mistaken for a sessil protein. The storage of either the complete hemoglobin molecule or the globin fraction causes the diffuse eosinophily in the ground substance of fixed cartilage which also blocks the determination of acid mucopolysaccharides (alcian blue staining method) as well as the metachromatic reaction of the ground substance.

     

Interaction of hydroxylated collagen IV with the von hippel-lindau tumor suppressor

The von Hippel-Lindau tumor suppressor (pVHL) targets hydroxylated alpha-subunits of hypoxia-inducible factor (HIF) for ubiquitin-mediated proteasomal destruction through direct interaction with the hydroxyproline binding pocket in its beta-domain. Although disruption of this process may contribute to VHL-associated tumor predisposition by up-regulation of HIF target genes, genetic and biochemical analyses support the existence of additional functions, including a role in the assembly of extracellular matrix. In an attempt to delineate these pathways, we searched for novel pVHL-binding proteins. Here we report a direct, hydroxylation-dependent interaction with alpha-chains of collagen IV. Interaction with pVHL was also observed with fibrillar collagen chains, but not the folded collagen triple helix. The interaction was suppressed by a wide range of tumor-associated mutations, including those that do not disturb the regulation of HIF, supporting a role in HIF-independent tumor suppressor functions.