Hepatitis C virus (HCV) infection causes chronic liver diseases and is a global public health problem. Detailed analyses of HCV have been hampered by the lack of viral culture systems. Subgenomic replicons of the JFH1 genotype 2a strain cloned from an individual with fulminant hepatitis replicate efficiently in cell culture. Here we show that the JFH1 genome replicates efficiently and supports secretion of viral particles after transfection into a human hepatoma cell line (Huh7). Particles have a density of about 1.15–1.17 g/ml and a spherical morphology with an average diameter of about 55 nm. Secreted virus is infectious for Huh7 cells and infectivity can be neutralized by CD81-specific antibodies and by immunoglobulins from chronically infected individuals. The cell culture–generated HCV is infectious for chimpanzee. This system provides a powerful tool for studying the viral life cycle and developing antiviral strategies.

Production of infectious hepatitis C virus in tissue culture from a cloned viral genome

Organic Chemistry By Dr. I. L. Finar. Vol. 2: Stereochemistry and the Chemistry of Natural Products. Pp. xi + 733. (London and New York: Longmans, Green and Co., Ltd., 1956.) 40s. net.

Advanced Organic Chemistry

There is growing recognition that many phenolic secondary metabolites present in foodstuffs may possibly exert beneficial effects on human health. This may to some degree be mediated via antioxidant actions, but a range of more specific pharmacological effects have also been proposed. Given this background, there may be favourable consequences for the general health of Western populations as a result of optimising the phenolic content of the diet. This paper reviews what is known of the function of phenolics both in the plant and in man. It also describes current understanding of the biosynthesis of phenolics in plants, with emphasis on where potential controlling steps may exist. Finally, advances in identification and isolation of the genes coding for phenolic biosynthetic enzymes or regulatory proteins are also summarised. Taken together, this information provides a basis for attempts to modify and optimise the phenolic content of food crops, using either conventional plant breeding along with manipulation of agronomic practices, or else the more targeted approaches of modern molecular biology.



© 2000 Society of Chemical Industry

Phenols in the plant and in man. The potential for possible nutritional enhancement of the diet by modifying the phenols content or profile

Plant cell walls represent the most abundant renewable resource on this planet. Despite their great abundance, only 2% of this resource is currently used by humans. Hence, research into the feasibility of using plant cell walls in the production of cost-effective biofuels is desirable. The main bottleneck for using wall materials is the recalcitrance of walls to efficient degradation into fermentable sugars. Manipulation of the wall polysaccharide biosynthetic machinery or addition of wall structure-altering agents should make it possible to tailor wall composition and architecture to enhance sugar yields upon wall digestion for biofuel fermentation. Study of the biosynthetic machinery and its regulation is still in its infancy and represents a major scientific and technical research challenge. Of course, any change in wall structure to accommodate cost-efficient biofuel production may have detrimental effects on plant growth and development due to the diverse roles of walls in the life of a plant. However, the diversity and abundance of wall structures present in the plant kingdom gives hope that this challenge can be met.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-313X.2008.03463.x

Cell‐wall carbohydrates and their modification as a resource for biofuels

Because lignin limits the use of wood for fiber, chemical, and energy production, strategies for its downregulation are of considerable interest. We have produced transgenic aspen (Populus tremuloides Michx.) trees in which expression of a lignin biosynthetic pathway gene Pt4CL1 encoding 4-coumarate:coenzyme A ligase (4CL) has been downregulated by antisense inhibition. Trees with suppressed Pt4CL1 expression exhibited up to a 45% reduction of lignin, but this was compensated for by a 15% increase in cellulose. As a result, the total lignin–cellulose mass remained essentially unchanged. Leaf, root, and stem growth were substantially enhanced, and structural integrity was maintained both at the cellular and whole-plant levels in the transgenic lines. Our results indicate that lignin and cellulose deposition could be regulated in a compensatory fashion, which may contribute to metabolic flexibility and a growth advantage to sustain the long-term structural integrity of woody perennials.

Biotechnology on genetic control of lignin biosynthesis in trees -Repression of lignin biosynthesis promotes cellulose accumulation and growth in transgenic trees-

To clarify the morphology of hepatitis C virus (HCV), an indirect immunogold electron microscopic study was carried out on two plasma samples with high HCV RNA titres using polyclonal and monoclonal antibodies specific to the putative HCV envelope protein. Spherical virus-like particles, 55 to 65 nm in diameter with spike-like projections, were found in 1.14 to 1.16 g/ml fractions after sucrose density gradient centrifugation. These particles were found only in HCV-infected blood donors and had morphological features similar to those of flaviviruses. Moreover, these particles specifically reacted with the polyclonal and monoclonal antibodies to the putative HCV envelope protein. This is the first known report in which the morphology of the HCV particle is clearly shown.

Hepatitis C virus particle detected by immunoelectron microscopic study

Wood from forest trees modified for more cellulose or hemicelluloses could be a major feedstock for fuel ethanol. Xylan and glucomannan are the two major hemicelluloses in wood of angiosperms. However, little is known about the genes and gene products involved in the synthesis of these wood polysaccharides. Using Populus trichocarpa as a model angiosperm tree, we report here a systematic analysis in various tissues of the absolute transcript copy numbers of cellulose synthase superfamily genes, the cellulose synthase (CesA) and the hemicellulose-related cellulose synthase-like (Csl) genes. Candidate Csl genes were characterized for biochemical functions in Drosophila Schneider 2 (S2) cells. Of the 48 identified members, 37 were found expressed in various tissues. Seven CesA genes are xylem specific, suggesting gene networks for the synthesis of wood cellulose. Four Csl genes are xylem specific, three of which belong to the CslA subfamily. The more xylem-specific CslA subfamily is represented by three types of members: PtCslA1, PtCslA3, and PtCslA5. They share high sequence homology, but their recombinant proteins produced by the S2 cells exhibited distinct substrate specificity. PtCslA5 had no catalytic activity with the substrates for xylan or glucomannan. PtCslA1 and PtCslA3 encoded mannan synthases, but PtCslA1 further encoded a glucomannan synthase for the synthesis of (1→4)-β-d-glucomannan. The expression of PtCslA1 is most highly xylem specific, suggesting a key role for it in the synthesis of wood glucomannan. The results may help guide further studies to learn about the regulation of cellulose and hemicellulose synthesis in wood.

The cellulose synthase gene superfamily and biochemical functions of xylem-specific cellulose synthase-like genes in Populus trichocarpa.

Lignans and norlignans constitute abundant classes of phenylpropanoids. Biosynthesis of these compounds has received widespread interest, mainly because they have various clinically important biological activities. In addition, lignans and norlignans are often biosynthesized and deposited in significant amounts in the heartwood region of trees as a metabolic event of heartwood formation, probably preventing heart rot by heart-rot fungi. Furthermore, biosynthetic reactions of lignans and norlignans involve unique stereochemical properties that are of great interest in terms of bioorganic chemistry and are expected to provide a model for biomimetic chemistry and its application. We outline the recent advances in the study of lignan and norlignan biosynthesis.

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Biosynthesis of lignans and norlignans

For research and development of plants suitable for forage and biofuel production, the development of a high-throughput system of lignin determination, especially for herbaceous species, is important. However, currently available methods for lignin determination are not suitable for high-throughput analysis of herbaceous samples. In this paper, we describe a straightforward, high-throughput method for lignin determination as thioglycolic acid lignin from rice straw using disposable plastic microtubes, TissueLyser, and a UV microplate reader. We successfully plotted calibration curves derived from the readings of a spectrophotometer and a microplate reader using thioglycolic acid lignin prepared from bamboo milled wood lignin as a lignin standard. Based on the calibration curve, we could determine the lignin content in various organs from dried rice straw and rice seedlings. We confirmed that 20 mg of dried material from rice plants is adequate for stable determination of the lignin content. Using this method, 100 independent samples from rice straw can be analyzed in three days per person.

Shiro Suzuki

Papers

Hepatitis C virus particle detected by immunoelectron microscopic study

The cellulose synthase gene superfamily and biochemical functions of xylem-specific cellulose synthase-like genes in Populus trichocarpa.

Biosynthesis of lignans and norlignans

High-throughput determination of thioglycolic acid lignin from rice

Characterization of Arabidopsis thaliana pinoresinol reductase, a new type of enzyme involved in lignan biosynthesis.