Redox regulation of chloroplast enzymes in Galdieria sulphuraria in view of eukaryotic evolution

Redox modulation is a general mechanism for enzyme regulation, particularly for the post-translational regulation of the Calvin cycle in chloroplasts of green plants. Although red algae and photosynthetic protists that harbor plastids of red algal origin contribute greatly to global carbon fixation, relatively little is known about post-translational regulation of chloroplast enzymes in this important group of photosynthetic eukaryotes. To address this question, we used biochemistry, phylogenetics and analysis of recently completed genome sequences. We studied the functionality of the chloroplast enzymes phosphoribulokinase (PRK, EC 2.7.1.19), NADP-dependent glyceraldehyde 3-phosphate dehydrogenase (NADP-GAPDH, GapA, EC 1.2.1.13), fructose 1,6-bisphosphatase (FBPase, EC 3.1.3.11) and glucose 6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49), as well as NADP-malate dehydrogenase (NADP-MDH, EC 1.1.1.37) in the unicellular red alga Galdieria sulphuraria (Galdieri) Merola. Despite high sequence similarity of G. sulphuraria proteins to those of other photosynthetic organisms, we found a number of distinct differences. Both PRK and GAPDH co-eluted with CP12 in a high molecular weight complex in the presence of oxidized glutathione, although Galdieria CP12 lacks the two cysteines essential for the formation of the N-terminal peptide loop present in higher plants. However, PRK inactivation upon complex formation turned out to be incomplete. G6PDH was redox modulated, but remained in its tetrameric form; FBPase was poorly redox regulated, despite conservation of the two redox-active cysteines. No indication for the presence of plastidic NADP-MDH (and other components of the malate valve) was found.     

New bioengineering insights into human neural precursor cell expansion in culture

Understanding initial cell growth, interactions associated with the process of expansion of human neural precursor cells (hNPCs), and cellular events pre- and postdifferentiation are important for developing bioprocessing protocols to reproducibly generate multipotent cells that can be used in basic research or the treatment of neurodegenerative disorders. Herein, we report the in vitro responses of telencephalon hNPCs grown in a serum-free growth medium using time-lapse live imaging as well as cell-surface marker, aggregate size, and immunocytochemical analyses. Time-lapse analysis of hNPC initial expansion indicated that cell-surface attachment in stationary culture and the frequency of cell-cell interaction in suspension conditions are important for subsequent aggregate formation and hNPC growth. In the absence of cell-surface attachment in low-attachment stationary culture, large aggregates of cells were formed and expansion was adversely affected. The majority of the telencephalon hNPCs expressed CD29, CD90, and CD44 (cell surface markers involved in cell-ECM and cell-cell interactions to regulate biological functions such as proliferation), suggesting that cell-surface attachment and cell-cell interactions play a significant role in the subsequent formation of cell aggregates and the expansion of hNPCs. Before differentiation, about 90% of the cells stained positive for nestin and expressed two neural precursor cells surface markers (CD133 and CD24). Upon withdrawal of growth cytokines, hNPCs first underwent cell division and then differentiated preferentially towards a neuronal rather than a glial phenotype. This study provides key information regarding human NPC behavior under different culture conditions and favorable culture conditions that are important in establishing reproducible hNPC expansion protocols.     

Advances in soil microbial ecology and the biodiversity

Recent studies on the colony formation of soil bacteria opened the way to categorize soil bacteria into colony forming curve (CFC) groups of different growth rates. A bacterial culture collection comprising organisms from every CFC group is called an ecocollection. Outlines of ECs of paddy soil 1992 and grassland soil 1987 and 1992 were described. Phylogenetic studies by 16S rDNA sequencing showed a great diversity of culture strains of the ecocollections (EC). A set of alternative concepts was proposed; the active and the quiescent forms of bacterial cells in soil. The former is able to be cultivated and thus counted by the plate method, while the latter is not unless it transforms into the former. Based on the results several points required for extensive cataloguing of soil bacteria were noted.     

A Genomic and Molecular View of Wood Formation

Wood formation is a process derived from plant secondary growth. Different from primary growth, plant secondary growth is derived from cambium meristem cells in the vascular and cork cambia and leads to the girth increase of the plant trunk. In the secondary growth process, plants convert most of photosynthesized products into various biopolymers for use in the formation of woody tissues. This article summarizes the new developments of genomic and genetic characterization of wood formation in herbaceous model plant and tree plant systems. Genomic studies have categorized a collection of the genes for which expression is associated with secondary growth. During wood formation, the expression of many genes is regulated in a stage-specific manner. The function of many genes involved in wood biosyntheses and xylem differentiation has been characterized. Although great progress has been achieved in the molecular and genomic understanding of plant secondary growth in recent years, the profound genetic mechanisms underlying this plant development remain to be investigated. Completion of the first tree genome sequence (Populus genome) provides a valuable genomic resource for characterization of plant secondary growth.     

Effects of captivity and testosterone on the volumes of four brain regions in the dark‐eyed junco (Junco hyemalis)

This study investigates the effects of captivity and testosterone treatment on the volumes of brain regions involved in processing visual and spatial information in adult dark‐eyed juncos (Junco hyemalis). We treated captive and free‐living male juncos with either testosterone‐filled or empty implants. Captive juncos had a smaller hippocampal formation (HF) (both in absolute volume and relative to telencephalon) than free‐living birds, regardless of hormone treatment. Testosterone‐treated males (both captive and free‐living) had a smaller telencephalon and nucleus rotundus, but not a smaller HF or ectostriatum, than controls. We found that free‐living testosterone‐treated males had larger home ranges than free‐living controls in agreement with earlier experiments, but we found no corresponding difference in HF volume. We discuss the implications of the effect of captivity on HF volume for past and future laboratory experiments. © 2000 John Wiley & Sons, Inc. J Neurobiol 43: 244–253, 2000     

Developmentally regulated expression of a cell surface protein,neuropilin, in the mouse nervous system

Neuropilin (previously A5) is a cell surface glycoprotein that was originally identified in Xenopus tadpole nervous tissues. In Xenopus, neuropilin is expressed on both the presynaptic and postsynaptic elements in the visual and general somatic sensory systems, suggesting a role in neuronal cell recognition. In this study, we identified a mouse homologue of neuropilin and examined its expression in developing mouse nervous tissues. cDNA cloning and sequencing revealed that the primary structure of the mouse neuropilin was highly similar to that of Xenopus and that the extracellular segment of the molecule possessed several motifs that were expected to be involved in cell-cell interaction. Immunohistochemistry and in situ hybridization analyses in mice indicated that the expression of neuropilin was restricted to particular neuron circuits. Neuropilin protein was localized on axons but not on the somata of neurons. The expression of neuropilin persisted through the time when axons were actively growing to form neuronal connections. These observations suggest that neuropilin is involved in growth, fasciculation, and targeting for a particular groups of axons. © 1996 John Wiley & Sons, Inc.     

Genetic Interaction between the ero1-1 and leu2 Mutations in Saccharomyces cerevisiae

The conditional ero1-1 mutant, deficient in the ER-localized PDI oxidase Ero1p, is blocked in disulfide bond formation under restrictive conditions, such as high temperature, lack of oxygen, or high concentrations of membrane-permeant thiols. Previous studies of the physiological consequences of the ero1-1 mutation were carried out in a leu2 mutant. The ero1-1 leu2 strain does not grow in standard synthetic complete medium at 30 °C, a defect that can be remedied by increasing the L-leucine concentration in the medium or by transforming the ero1-1 leu2 strain with the LEU2 wild-type allele. In addition, the LEU2 gene can partially complement the growth impairment at 37 °C of the ero1-1 leu2 mutant. The leucine transporter Bap2p exhibits a dramatic decrease in stability in an ero1-1 strain, which may account for the pronounced leucine demand observed in the ero1-1 leu2 mutant.     

Remodeling of nuclear architecture during the cell cycle in Drosophila embryos

Little is known about what determines the nuclear matrix or how its reorganization is regulated during mitosis. In this study we report on a monoclonal antibody, mAb2A, which identifies a novel nuclear structure in Drosophila embryos which forms a diffuse meshwork at interphase but which undergoes a striking reorganization into a spindle-like structure during pro- and metaphase. Double labelings with α-tubulin and mAb2A antibodies demonstrate that the microtubules of the mitotic apparatus co-localize with this mAb2A labeled structure during metaphase, suggesting it may serve a role in microtubule spindle assembly and/or function during nuclear division. That the mAb2A-labeled nuclear structure is essential for cell division and/or maintenance of nuclear integrity was directly demonstrated by microinjection of mAb2A into early syncytial embryos which resulted in a disintegration of nuclear morphology and perturbation of mitosis. © 1996 Wiley-Liss, Inc.     

Microbial populations and activities in the rhizoplane of rock-weathering desert plants. II. Growth promotion of cactus seedlings

Four bacterial species isolated from the rhizoplane of cacti growing in bare lava rocks were assessed for growth promotion of giant cardon cactus seedlings (Pachycereus pringlei). These bacteria fixed N(2), dissolved P, weathered extrusive igneous rock, marble, and limestone, and significantly mobilized useful minerals, such as P, K, Mg, Mn, Fe, Cu, and Zn in rock minerals. Cardon cactus seeds inoculated with these bacteria were able to sprout and grow normally without added nutrients for at least 12 months in pulverized extrusive igneous rock (ancient lava flows) mixed with perlite. Cacti that were not inoculated grew less vigorously and some died. The amount of useful minerals (P, K, Fe, Mg) for plant growth extracted from the pulverized lava, measured after cultivation of inoculated plants, was significant. This study shows that rhizoplane bacteria isolated from rock-growing cacti promote growth of a cactus species, and can help supply essential minerals for a prolonged period of time.     

The Functional Interrelationship between Gap Junctions and Fenestrae in Endothelial Cells of the Liver Organoid

Functional intact liver organoid can be reconstructed in a radial-flow bioreactor when human hepatocellular carcinoma (FLC-5), mouse immortalized sinusoidal endothelial M1 (SEC) and A7 (HSC) hepatic stellate cell lines are cocultured. The structural and functional characteristics of the reconstructed organoid closely resemble the in vivo liver situation. Previous liver organoid studies indicated that cell-to-cell communications might be an important factor for the functional and structural integrity of the reconstructed organoid, including the expression of fenestrae. Therefore, we examined the possible relationship between functional intact gap junctional intercellular communication (GJIC) and fenestrae dynamics in M1-SEC cells. The fine morphology of liver organoid was studied in the presence of (1) irsogladine maleate (IM), (2) oleamide and (3) oleamide followed by IM treatment. Fine ultrastructural changes were studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) and compared with control liver organoid data. TEM revealed that oleamide affected the integrity of cell-to-cell contacts predominantly in FLC-5 hepatocytes. SEM observation showed the presence of fenestrae on M1-SEC cells; however, oleamide inhibited fenestrae expression on the surface of endothelial cells. Interestingly, fenestrae reappeared when IM was added after initial oleamide exposure. GJIC mediates the number of fenestrae in endothelial cells of the liver organoid.