| POLYMERS Vol.66 No.6 |
| >> Japanese | >> English |
COVER STORY
Plant Biotechnology and Polymer Science: From Biomass-Based Materials to Polymer-Based Plant Science |
| COVER STORY: Highlight Reviews |
| Toward Total Elucidation of Biosynthetic Mechanism of Natural Rubber | Seiji TAKAHASHI, Satoshi YAMASHITA, Kazuhisa FUSHIHARA |
| <Abstract> Natural rubber (NR), mainly consisting of cis-1,4-polyisoprene with a few trans-isoprene units at the ω-terminus, is a non-fungible natural polymer used for manufacturing rubber products such as tyres because of its unique physical properties. Industrial NR production depends solely on latex, the cytoplasm of laticifers in vascular tissues, from the Para rubber tree (Hevea brasiliensis). In latex, NR exists as the rubber particle (RP), which is a specialized organelle, and primarily consists of a hydrophobic rubber core enclosed by a lipid monolayer. To meet the ever-increasing demand for NR, molecular breeding and metabolic engineering of H. brasiliensis for improvement of the NR production are required. Here, we review molecular mechanisms for the NR biosynthesis elucidated so far. Recent important progress in the functional identification of key enzymes in the NR biosynthetic pathway enables us to synthesize extraordinary long-chain polyisoprenoids corresponding to NR in vitro by using the NR biosynthetic machinery reconstituted on RPs. Keywords: Isoprenoid / Hevea brasiliensis / Latex / Natural Rubber / Prenyltransferase / Rubber Particle |
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| Mechanisms on Biosynthesis of Woody Macromolecule as Structural Materials | Taku DEMURA, Misato OHTANI |
| <Abstract> Woody macromolecules (WMMs) derived from plant cell walls, especially from highly thickened secondary cell walls (SCWs) of woody cells, can be utilized for structural materials. WMMs includes three major SCW polymers, cellulose, xylan, and lignin. To understand the functional property of WMMs and then utilize WMMs effectively, it is pivotal to understand the molecular mechanisms underlying biosynthesis of these SCW polymers. Recent researches using in vitro cell culture systems, in which biosynthesis of SCWs can be induced, successfully identified master transcriptional regulators, VASCULAR-RELATED NAC DOMAIN (VND) genes, for the biosyntheisis of SCWs. Analysis of the VND genes revealed the transcriptional regulatory network where VNDs induce the expression of genes for biosynthesis of SCW polymers through the activation of another group of transcription factors, MYBs. In addition, an inductive activation of VND activities allowed us to understand the molecular mechanisms of the SCW polymer biosynthesis. In this chaper, we descirbed recent important findings for the biosynthetic mechanisms of SCW polymers. Keywords: Cellulose / Lignin / Secondary Cell Wall / Transcriptional Regulatory Network / VND Transcription Factors / Woody Macromolecule / Xylan |
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| Highly Functional Materials Based on Structural Polysaccharides | Yoshiyuki NISHIO, Kazuki SUGIMURA |
| <Abstract> Structural polysaccharides represented by cellulose are sustainable bioresources and high-potential polymers to be further materialized for both commodity and specialty uses. In a current trend, much interest and work are directed toward the design and construction of high-functional material systems based on cellulose and related polysaccharides by exploiting and improving their nano- and mesoscopic characteristics. For example, we can find several successful results in recent studies on the following subjects: polymer composites reinforced with cellulose nanocrystals (CNCs) as rod-like nanofiller; inorganic hybridization using liquid crystals of CNCs or cellulose derivatives as template; incorporation of iron oxide nanoparticles into CNC/sea-weed polysaccharide gels; and so on. The fabricated materials each exhibit up-to-data thermomechanical, optical, magnetic, or other specific functionality suggestible for multifaceted prospective applications. Some comments and the outlook for future explorations are offered in this review article on modern polysaccharides. Keywords: Polysaccharides / Cellulose / Nanocrystal / Derivatives / Mesoscopic Characteristics / Polymer Composites / Inorganic Hybridization / Functional Materials |
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| COVER STORY: Topics and Products |
| Heterologous Expression of Cellulose Synthases and Trial of Synthesis of Cellulose in vitro to Elucidate the Mechanism of Cellulose Synthesis in Nature | Naoki SUNAGAWA, Kenji TAJIMA, Masahiro SAMEJIMA, Kiyohiko IGARASHI |
| <Abstract> Cellulose is one of the major carbohydrate on the earth and is utilized in humankind life as a major component of plant materials. Most of terrestrial cellulose is produced by land plant, however it is also found in some algae, tunicates and various bacteria species. Since cellulose biosynthetic process is a complicated system, details are still unknown. To solve this issue, we attempt to make a heterogonous expression system and trying a dynamic visualization of this synthesis process. In this paper, to carry out the approaches, we will report the construction of the recombinant expression system of bacterial cellulose synthase (GxCeSAB) and plant cellulose synthase (AtCeSA1) in the yeast Pichia pastoris. Keywords: Cellulose / Cellulose Biosynthesis / Pichia Expression System |
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| Plant Genetic Transformation and Genome Editing | Takeshi YOSHIZUMI |
| <Abstract> Genome editing is a powerful technique to manipulate the genome precisely and provides strong impacts on basic plant biology and also crop breeding. In case of plants, genome editing relies on genetic transformation because edited plants should be isolated from transgenic plants expressing genome editing machineries. Then transformation methods are important for genome editing in plants. DNA is not so easy to access in plant cells directly, which are sorrounded by cell walls, so that well-known sophisticated animal transformation techniques are not directly applicable to plants. In addition to genome editing, we are introducing plant specific transformation methods in our approach to this topic. We developed peptide-based DNA carriers composed of two peptide blocks (DNA binding peptide and sub-cellular localization signal). The peptides can deliver not only nucleic acids (DNA and RNA) but also proteins into the plant cytosol, mitochondria, and chloroplasts. We also discuss applications of our peptides to nuclear genome editing and organellar genome editing and the future prospects in plant breeding. Keywords: Peptide / Genome Editing / Gene Delivery / Trnaformation / Organellar Genome / Chloroplast / Mitochondria |
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| Extraction and Utilization of Macromolecular Components of Plants via a Sustainable Process | Kazuhiro SHIKINAKA |
| <Abstract> In this paper, an utilization of polysaccarides and lignin, plant biomass, via a sustainable process is described. Here, we report a simple yet effective method for processing plant biomass by combined wet-type ultrafine bead milling and enzymatic saccharification at pH 5.0 and 50℃. This generates nanoscale particles without loss of plant biomass that allows close to 70% saccharification of cellulose for cedar and recovery of a glassy, flame retardant, and a transparent non-deteriorated lignin film. Furthermore, due to the non-formation of chemical inhibitors from the non-toxic reaction process, the alcohol bioconversion of the generated sugars with a maximum theoretical value is achieved. The almost full recovery of other un-deteriorated plant biomass components, which has a positive impact on the generation of high value secondary products, could considerably contribute to its economic viability as well. The convergence of lignin to a functional monomer and its utilization as a polymer unit is also described. Keywords: Plant Biomass / Polysaccharides / Lignin / Bioehtanol / 2-Pyrone-4,6-Dicarboxylic Acid |
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| Polymer Science and I: A Personal Account |
| A Theme Comes Around | Kousuke TSUCHIYA |
| <Abstract> My first research theme during my bachelor course, regarding to synthesis of polypeptides, was not completed due to my immature research skill. After I changed the affiliation several times, I had an opportunity again to do a research concerning the polypeptide materials. |
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| Front-Line Polymer Science |
| Polymers Synthesized from Plant Biomass | Toshihiko OOI, Ken’ichiro MATSUMOTO, Seiichi TAGUCHI |
| <Abstract> Plant-derived biomass has attracted considerable research interest as potent resources for polymer synthesis. This review article introduces recent studies on polymer production by utilizing lignocellulose-derived mono sugars, polysaccharides and plant oils. Plant-derived polysaccharides such as xylan and glucomannan can be derivatized into plastic material by esterification of hydroxyl groups using short-chain-length fatty acids. After lignin removal, the polysaccharides are degraded into mono sugars, such as xylose, which can serve as efficient starting substance for various polymers. Furfural is one of the potent derivatives of xylose, which can be used for productions of aromatic polymers, including polyethyleneterephthalate. Xylose is also used for the production of unusual lactate-based polyhydroxyalkanoate (PHA) using an engineered bacterial platform. Modified bacteria with acquired polysaccharide-degrading activity directly utilize polysaccharides as feedstock. A different class of PHAs, called homo medium-chain-lenght PHA, is synthesized from plant oils. The Epoxides of plant oils are used as monomeric constituents for production of biobased and functionalized polymers, such as shape-memory materials. Keywords: Plant Biomass / Polysaccharides / Plant Oils / Xylose / Xylan / PHA / PLA / Furfural |
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