Iron deficiency differently affects metabolic responses in soybean roots

Iron deficiency responses were investigated in roots of soybean, a Strategy I plant species. Soybean responds to iron deficiency by decreasing growth, both at the root and shoot level. Chlorotic symptoms in younger leaves were evident after a few days of iron deficiency, with chlorophyll content being dramatically decreased. Moreover, several important differences were found as compared with other species belonging to the same Strategy I. The main differences are (i) a lower capacity to acidify the hydroponic culture medium, that was also reflected by a lower H(+)-ATPase activity as determined in a plasma membrane-enriched fraction isolated from the roots; (ii) a drastically reduced activity of the phosphoenolpyruvate carboxylase enzyme; (iii) a decrease in both cytosolic and vacuolar pHs; (iv) an increase in the vacuolar phosphate concentration, and (v) an increased exudation of organic carbon, particularly citrate, phenolics, and amino acids. Apparently, in soybean roots, some of the responses to iron deficiency, such as the acidification of the rhizosphere and other related processes, do not occur or occur only at a lower degree. These results suggest that the biochemical mechanisms induced by this nutritional disorder are differently regulated in this plant. A possible role of inorganic phosphate in the balance of intracellular pHs is also discussed.     

Enterocin 226NWC, a bacteriocin produced by Enterococcus faecalis 226, active against Listeria monocytogenes

F. VILLANI, G. SALZANO, E. SORRENTINO, O. PEPE, P. MARINO AND S. COPPOLA. 1993. Enterococcus faecalis 226, isolated from natural whey cultures utilized as starters in the manufacture of mozzarella cheese from water-buffalo milk, produces a bacteriocin designated enterocin 226NWC. The bacteriocin was isolated from culture supernatant fluids of the producer strain and was active against strains of the same species and Listeria monocytogenes, but not against useful lactic acid bacteria. Enterocin 226NWC is a protein with an apparent molecular weight of about 5800; it is relatively heat-stable and has a bactericidal mode of action. Listeria monocytogenes, growing in the presence of the enterocin 226NWC producer strain in broth and in reconstituted skim milk, was inhibited.     

Different signal transduction by epidermal growth factor may be responsible for the difference in modulation of amino acid transport between fetal and adult hepatocytes

[1-¹⁴C]-2-aminoisobutyric acid (AIB) uptake and signal transduction pattern after epidermal growth factor (EGF) stimulation were examined in freshly isolated hepatocytes from 20-day-old fetuses and 3-month-old rats. EGF induced a transient increase of AIB transport after 10 min only in adult animals; the observed unresponsiveness of fetal liver is not dependent on a lack of EGF receptors which are present though to a lesser extent on the plasma membrane in this period. As far as the production of the second messengers, inositol trisphosphate (IP₃) and calcium, is concerned, substantial differences were found: EGF increased IP₃ production in adult hepatocytes, whereas it had no effect in fetal ones. Moreover, the addition of EGF induced a calcium transient in hepatocytes from adult animals, while there was no increase in fetal cells. The lack of EGF effect on amino acid transport in fetal cells could be due to its inability to produce both IP₃ and calcium transients, suggesting that this transduction pathway is not activated during fetal life.     

Redundancy in tumor necrosis factor (TNF) and lymphotoxin (LT) signaling in vivo: mice with inactivation of the entire TNF/LT locus versus single-knockout mice

Homologous genes and gene products often have redundant physiological functions. Members of the tumor necrosis factor (TNF) family of cytokines can signal activation, proliferation, differentiation, costimulation, inhibition, or cell death, depending on the type and status of the target cell. TNF, lymphotoxin alpha (LTalpha), and LTbeta form a subfamily of a larger family of TNF-related ligands with their genes being linked within a compact 12-kb cluster inside the major histocompatibility complex locus. Singly TNF-, LTalpha-, and LTbeta-deficient mice share several phenotypic features, suggesting that TNF/LT signaling pathways may regulate overlapping sets of target genes. In order to directly address the issue of redundancy of TNF/LT signaling, we used the Cre-loxP recombination system to create mice with a deletion of the entire TNF/LT locus. Mice with a triple LTbeta/TNF/LTalpha deficiency essentially manifest a combination of LT and TNF single-knockout phenotypes, except for microarchitecture of the spleen, where the disorder of lymphoid cell positioning and functional T- and B-cell compartmentalization is severer than that found in TNF or LT single-knockout mice. Thus, our data support the notion that TNF and LT have largely nonredundant functions in vivo.     

Localization of stilbene synthase in Vitis vinifera L. during berry development

The localization of stilbene synthase (STS) (EC 2.3.1.95) in grape berry (Vitis vinifera L.) was investigated during fruit development. The berries were collected at 2, 4, 7, 11, and 15 weeks postflowering from the cultivar Nebbiolo during the 2005 and 2006 growing seasons. High-performance liquid chromatography analysis showed that berries accumulated cis- and trans-isomers of resveratrol mainly in the exocarp throughout fruit development. Immunodetection of STS protein was performed on berry extracts and sections with an antibody specifically developed against recombinant grape STS1. In agreement with resveratrol presence, STS was found in berry exocarp tissues during all stages of fruit development. The labeled epidermal cells were few and were randomly distributed, whereas nearly all the outer hypodermis cells were STS-positive. The STS signal decreased gradually from exocarp to mesocarp, where the protein was detected only occasionally. At the subcellular level, STS was found predominantly within vesicles (of varying size), along the plasma membrane and in the cell wall, suggesting protein secretion in the apoplast compartment. Despite the differences in fruit size and structure, the STS localization was the same before and after veraison, the relatively short developmental period during which the firm green berries begin to soften and change color. Nevertheless, the amount of protein detected in both exocarp and mesocarp decreased significantly in ripe berries, in agreement with the lower resveratrol content measured in the same tissues. The location of STS in exocarp cell wall is consistent with its role in synthesizing defense compounds and supports the hypothesis that a differential localization of phenylpropanoid biosynthetic machinery regulates the deposition of specific secondary products at different action sites within cells.     

Sex estimation using the first cervical vertebra

The articular surfaces and vertebral foramen area of the first cervical vertebra are sexually dimorphic and can be used to sex complete or fragmentary specimens. Eight measurements were taken from the articular regions (superior and inferior) of 100 first cervical vertebrae from Terry collection specimens housed at the Smithsonian Institution. Seven regression and seven discriminant function equations were created that predict sex with 77–85% and 75–85% accuracy, respectively. In separate control tests, measurements from 100 first cervical vertebrae from Hamann-Todd collection individuals (Cleveland Museum of Natural History) and from 34 archaeological specimens were used with the Terry equations. The control samples were sexed with 60—85% accuracy. © 1995 Wiley-Liss, Inc.     

Structural and spectropotentiometric analysis of Blastochloris viridis heterodimer mutant reaction center

Heterodimer mutant reaction centers (RCs) of Blastochloris viridis were crystallized using microfluidic technology. In this mutant, a leucine residue replaced the histidine residue which had acted as a fifth ligand to the bacteriochlorophyll (BChl) of the primary electron donor dimer M site (HisM200). With the loss of the histidine-coordinated Mg, one bacteriochlorophyll of the special pair was converted into a bacteriopheophytin (BPhe), and the primary donor became a heterodimer supermolecule. The crystals had dimensions 400 × 100 × 100 μm, belonged to space group P4₃2₁2, and were isomorphous to the ones reported earlier for the wild type (WT) strain. The structure was solved to a 2.5 Å resolution limit. Electron-density maps confirmed the replacement of the histidine residue and the absence of Mg. Structural changes in the heterodimer mutant RC relative to the WT included the absence of the water molecule that is typically positioned between the M side of the primary donor and the accessory BChl, a slight shift in the position of amino acids surrounding the site of the mutation, and the rotation of the M194 phenylalanine. The cytochrome subunit was anchored similarly as in the WT and had no detectable changes in its overall position. The highly conserved tyrosine L162, located between the primary donor and the highest potential heme C₃₈₀, revealed only a minor deviation of its hydroxyl group. Concomitantly to modification of the BChl molecule, the redox potential of the heterodimer primary donor increased relative to that of the WT organism (772 mV vs. 517 mV). The availability of this heterodimer mutant and its crystal structure provides opportunities for investigating changes in light-induced electron transfer that reflect differences in redox cascades.     

Muscarinic receptor subtypes involved in hippocampal circuits

Muscarinic receptors modulate hippocampal activity in two main ways: inhibition of synaptic activity and enhancement of excitability of hippocampal cells. Due to the lack of pharmacological tools, it has not been possible to identify the individual receptor subtypes that mediate the specific physiological actions that underlie these forms of modulation. Light and electron microscopic immunocytochemistry using subtype-specific antibodies was combined with lesioning techniques to examine the pre- and postsynaptic location of m1-m4 mAChR at identified hippocampus synapses. The results revealed striking differences among the subtypes, and suggested different ways that the receptors modulate excitatory and inhibitory transmission in distinct circuits. Complementary physiological studies using m1-toxin investigated the modulatory effects of this subtype on excitatory transmission in more detail. The implications of these data for understanding the functional roles of these subtypes are discussed.