Biosynthesis of poly(3-hydroxyalkanoate) from amino acids

It was found that an optically active copolyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), denoted as P(3HB-co-3HV), is synthesized by Alcaligenes eutrophus H16 from several amino acids under various fermentation conditions. The optimum condition for the biosynthesis from one amino acid, threonine, was investigated and its biosynthetic pathway was discussed on the basis of the relation between the fermentation condition and the co-monomer composition of the produced polyesters.     

Diffusion of Fe(II) from an iron propagation cage and its effect on tissue iron and pigments of macroalgae on the cage

Iron propagation cages were settled on sand and/or rock beds in coastal areas of Hokkaido. The cage was oxidized by dissolved oxygen and the released Fe(II) diffused into the seawater around the cage. Fe(II) concentrations in the range of 10–50 nM were detected within a 20-m distance around the cage. For comparison, in the Japan Sea, the total iron concentration is less than 2 nM.Laminaria japonica was grown in an indoor semi-continuous culture system. The critical Fe level for maintaining maximum growth, and the subsistence Fe level for survival were measured. The concentrations obtained were 14–21 and 8 g Fe g^–1 tissue, respectively. Iron found inL. japonica growing on rocks and/or rock beds in the Japan Sea was close to the subsistence level. However, the Fe level inL. japonica on the cage in the Japan Sea was considerably higher. The concentrations of chlorophyll-a and fucoxanthin collected from the cage were significantly higher for sporophytes, demonstrating that iron is a very important element for the growth of seaweeds.     

A CD36-related Transmembrane Protein Is Coordinated with an Intracellular Lipid-binding Protein in Selective Carotenoid Transport for Cocoon Coloration

The transport pathway of specific dietary carotenoids from the midgut lumen to the silk gland in the silkworm, Bombyx mori, is a model system for selective carotenoid transport because several genetic mutants with defects in parts of this pathway have been identified that manifest altered cocoon pigmentation. In the wild-type silkworm, which has both genes, Yellow blood (Y) and Yellow cocoon (C), lutein is transferred selectively from the hemolymph lipoprotein to the silk gland cells where it is accumulated into the cocoon. The Y gene encodes an intracellular carotenoid-binding protein (CBP) containing a lipid-binding domain known as the steroidogenic acute regulatory protein-related lipid transfer domain. Positional cloning and transgenic rescue experiments revealed that the C gene encodes Cameo2, a transmembrane protein gene belonging to the CD36 family genes, some of which, such as the mammalian SR-BI and the fruit fly ninaD, are reported as lipoprotein receptors or implicated in carotenoid transport for visual system. In C mutant larvae, Cameo2 expression was strongly repressed in the silk gland in a specific manner, resulting in colorless silk glands and white cocoons. The developmental profile of Cameo2 expression, CBP expression, and lutein pigmentation in the silk gland of the yellow cocoon strain were correlated. We hypothesize that selective delivery of lutein to specific tissue requires the combination of two components: 1) CBP as a carotenoid transporter in cytosol and 2) Cameo2 as a transmembrane receptor on the surface of the cells.     

The expression of iron homeostasis-related genes during rice germination

To characterize Fe homeostasis during the early stages of seed germination, a microarray analysis was performed. mRNAs extracted from fully mature seeds or seeds harvested 1–3 days after sowing were hybridized to a rice microarray containing approximately 22,000 cDNA oligo probes. Many Fe deficiency-inducible genes were strongly expressed throughout early seed germination. These results suggest that the demand for Fe is extremely high during germination. Under Fe-deficient conditions, rice produces and secretes a metal-cation chelator called deoxymugineic acid (DMA) to acquire Fe from the soil. In addition, DMA and its intermediate nicotianamine (NA) are thought to be involved in long distance Fe transport in rice. Using promoter-β-glucuronidase (GUS) analysis, we investigated the expression patterns during seed germination of the Fe deficiency-inducible genes OsNAS1, OsNAS2, OsNAS3, OsNAAT1, and OsDMAS1, which encode enzymes that participate in the biosynthesis of DMA, and the transporter genes OsYSL2 and OsIRT1, which are involved in Fe transport. All of these genes were expressed in germinating seeds prior to protrusion of the radicle. These results suggest that DMA and NA are produced and involved in Fe transport during germination. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Mycolyltransferase-mediated glycolipid exchange in Mycobacteria

Trehalose dimycolate (TDM), also known as cord factor, is a major surface glycolipid of the cell wall of mycobacteria. Because of its potent biological functions in models of infection, adjuvancy, and immunotherapy, it is important to determine how its biosynthesis is regulated. Here we show that glucose, a host-derived product that is not readily available in the environment, causes Mycobacterium avium to down-regulate TDM expression while up-regulating production of another major glycolipid with immunological roles in T cell activation, glucose monomycolate (GMM). In vitro, the mechanism of reciprocal regulation of TDM and GMM involves competitive substrate selection by antigen 85A. The switch from TDM to GMM biosynthesis occurs near the physiological concentration of glucose present in mammalian hosts. We further demonstrate that GMM is produced in vivo by mycobacteria growing in mouse lung. These results establish an enzymatic pathway for GMM production. More generally, these observations provide a specific enzymatic mechanism for dynamic alterations of cell wall glycolipid remodeling in response to the transition from noncellular to cellular growth environments, including factors that are monitored by the host immune system.     

Immunological characterization of a 36 kDa Fe deficiency specific peptide in barley roots

In a previous paper we reported that an acidic 36 kDa peptide is the most strongly induced peptide among several peptides induced by Fe deficiency in barley roots. In this paper, polyclonal antibodies were raised against the 36 kDa peptide. This peptide appeared in the roots of all the graminaceous species tested (barley, rye, wheat, oat, maize, sorghum and rice) in response to Fe deficiency. More of the peptide was found in the roots of graminaceous species which secrete higher amounts of mugineic acids (MAs) under Fe deficient nutrition status. Induction of the 36 kDa peptide was first observed on the third day of Fe deficiency, rising to a maximum value on the seventh day. The trend has a positive correlation with secretion of MAs during Fe deficiency. Further, resupply of Fe resulted in a decrease in peptide production on the second day, reaching a control level on the seventh day. The rate of decrease in peptide production was observed to be slower than that of MA secretion. Other nutrient stresses such as B excess, B deficiency, Cu excess, Cu deficiency, Mn excess, Mn deficiency, Zn excess and Zn deficiency induced far less of the peptide. The specific expression of the 36 kDa peptide in roots of graminaceous species under Fe deficiency suggested the positive association of the peptide with a specific Fe deficiency tolerance mechanism in graminaceous plants.     

Age- and Sex-Dependency of Laser Speckle Flowgraphy Measurements of Optic Nerve Vessel Microcirculation

Purpose

To investigate the relationship between various characteristics of a normal population and laser speckle flowgraphy (LSFG) measurements of mean blur rate (MBR) in the optic nerve head (ONH).

Methods

A total of 189 eyes of 189 normal subjects (93 male, 96 female, mean age 45 ± 14 years old, age range: 20–72) without any history of hypertension, hyperlipidemia or diabetes were enrolled. ONH microcirculation was measured with LSFG and overall MBR (MA), vessel-area MBR (MV), and tissue-area MBR (MT) were derived from these measurements. The statistical association of these measurements with characteristics such as sex, age, intraocular pressure (IOP) and systolic blood pressure (SBP) was then determined.

Results

There was a trend towards decreased IOP and MV and increased SBP with age (P = 0.002, P = 0.035, and P = 0.006, respectively). Furthermore, IOP, MV and SBP were correlated with age (r = -0.23, P = 0.011; r = -0.24, P < 0.001; and r = 0.30, P < 0.001, respectively). Separate multiple regression analyses of independent contributing factors revealed that sex and IOP contributed to MA (P < 0.001 and P = 0.002, respectively), sex, IOP, and age contributed to MV (P < 0.001, P = 0.003, and P = 0.024, respectively), while only IOP contributed to MT (P = 0.003).

Conclusion

In a normal population, MBR was affected by IOP in both the large vessel and capillary areas of the ONH, but not by SBP. MV was also affected by age and sex, while MT was stable independent of age or sex.     

Mammalian ER stress sensor IRE1β specifically down-regulates the synthesis of secretory pathway proteins

Accumulation of unfolded proteins in the endoplasmic reticulum (ER) causes ER stress. The ER stress sensor inositol requiring enzyme-1beta (IRE1β), which is specifically expressed in intestinal epithelial cells, is thought to be involved in translational repression. However, its mechanism of action is not fully understood. Using a reporter that can evaluate and distinguish between translation efficiency in the cytosol and on the ER membrane, we show here that IRE1β represses translation on the ER membrane but not in the cytosol, and that this selective repression depends on the RNase activity of IRE1β.