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1、Plant cell and its wall,毛自朝 ,Outline of this charptor,Membrane structure Membrane organelles Cell wall and its architecture,Structure of membrane,The fluid-mosaic model This model emphasis the mosaic（镶嵌）:流动的酯双分子层中镶嵌着流动的蛋白 Fluid（流动性）：脂质是液晶态随温度变化而流动 （asymmetric) 对称性:different distribution of lipids an
2、d proteins,Plasma membrane,Lipid composition is highly variable Protein serve as variety function Electrochemical gradient produced by H+-ATPase driving many transport systems Several class of membrane mediate interaction with cell wall and receptor has been indentified,Interaction of endo-menbrane
3、system,Golgi Apparatus,TGN unit consist of morphologically distinct cisternae give rise to different type of coated vesicle Serve as carbohydrate factory,Xyloglucan,Pectic polysaccharides,Vacuoles,Cheaply produce large cell Multiple function including storage Digestion ,pH and ionic homeostasis, mic
4、robial defense ,sequestration of toxic compounds and pigmentation,The nucleus and its nuclear pore complex,Peroxisomes,Mitochondrion,Resemble prokaryotes Like all plastids ,are semi autonomous ,posses the genetic machinery to make some of its protein Cell power supplied station,Plastid and Chloropla
5、st,Thylakoid,Stacked grana,Interconnection stroma,Why cell wall important,(Chemically )Composed of polysaccharides ,proteins and aromatic substances (Structurally): middle lamella ,primary wall second wall Polysaccharide :Cellulose micro fibrils (scaffold), Hemicelluloses cross link the Cellulose mi
6、cro fibrils ,and the cellulose and hemicelluloses complex is embedded by pectin gel Cell wall is borne at cell plate and cell enlargement dependent on combination activities of endglycosidase ,endotransglycosidse ,and expansin Constitute major dietary fibers for human nutrition, used in wood paper a
7、nd textile product ,biomass for bio-energy and bio-chemicals .,Macromolecules of cell wall,Cellulose ,principle scaffolding component Cellulose scaffolding is interlocked by other glycan (hemicelluloses) Pectin matrix (rich galacturonic polymers )are fill between cell wall Structural protein are enc
8、oded by large gene famillies,Hemicelluloses,Two major flower plant : Xyloglucan (XyGs) Cross link the wall of dicots and one half of momocots Glucurono-arabino-xylan(GAXs) commelinoid (鸭跖草族)including bromeliads(凤梨科), palm (棕榈科)，gingers (姜科）Cypress（莎草科）and grasses(禾本种 ),XyGs,Liner chain of 1-4 b-D-gl
9、ucan Regularly o-6-glu unit was substituted with numerous a-D-Xyl Some of a-D-Xyl was further substituted by b-D-gal or a-L-Ara sometimes b-D-gal or a-L-Ara was further substituted by a-L-fuc.,GAX,Glucurono-arabino-xylan All angiosperms contain at least small amounts of GAXs As major cross lonk poly
10、mer In commelinoid monocots,Other link polymer,Mix linkage (1-3),(1-4)b Glucan Glucomannans Galactoglucomannans Galactomannans,Pectin matrix,Highly hydrated polysaccharides rich in D-galacturonic acid ,two fundamental constitutent areHGA (home galacturonan )and RGI (rhamno galacturonan I),and their
11、mofified form xylogalacturonan and rhamno galacturonanII(RGII) Dertermining wall porosity Providing charged suefaces that modulate pH and ion balance Regulating cell to cell adhesion Alert plant cell to presence of symbiotic organism ,pathogen and insects,Structural protein of cell wall,HRGPs (hydro
12、xy-proline rich glycoprotein ) PRPs(proline rich proteins) GRPs(glycine rich proteins) Arabinogalactan protein,Aromatic substance,Large fraction was hydroxyl-cinnamic acid (ferulic acid and coumaric acid),Cell wall architecture,Building block is coming from many way ,so does the architecture Primary
13、 cell is made of two, some times three structurally independent but interaction network,Wall of angiosperms are arranged in two different architecture,Type I cell wall Most dicots and non-commelinoid contain nearly equal amounts of XyGx and cellulose .with average 200 nm XyGx are enough to bind two
14、celllose microfibrilis. And XyGx , cellose network are embedded in pectin matrix two pectin layers are connected by salts bond of Ca2+,Type II cell wall 1.Commelinoid momocots cell wall 2.Similar with type I , instead of XyGx, GAX is the principle polymers to interlock the cellulose micro-fibrils 3.
15、pecin is less than typeI but GlA in GAX providing salts bond with Ca2+ 4.less structural protein by comparison with typeI ,but the accumulated extensive interconnection of phenylpropanoids,Cell wall biosynthesis and assembly,Originated from the developing cell plates During the telophase of mitotic
16、cell ,a phragmosome, was form by a flatten membrane vesicles contain cell wall components was arranged by cell cytoskeleton. ,except cellulose , polysaccharides, structural protein, and a broad spectrum cell synthesis enzyme were secreted by Golgi apparatus derived vesicles,Polysaccharides synthesis
17、 precursor ,sugar nucleotide,Sugar nucleotide inter-converting was found in Golgi body Sugar nucleotide formation occurred in two distinct pathway De nova and salvage,Monosaccharides conversion,洋芹糖,Cellulose micro-fibrils are assembled at plasma membrane,The only polymer are made outside membrane ar
18、e cellulose and callose Celluse synthase is mutipleunits complex Isoform of sucrose synthase can split sucrose into UDP-glc Callose synthases located in cell membrane is activates by damage of cellulose and callose Celluse synthase for plant defense abio and bio invading,Genes of cellulose synthase,
19、Base on homologous analysis of genes of cellulose synthases in Acetobacterium xylinum and Agrobacterium tumefaciens Deborah Delmer and colleagues coned celA gene in cotton Genome of Arabidopsis containing several Cotton homologs celA,Cell wall and cell growth,Cell expansion involves extensive change
20、s in the mass and composition occurring expansion or elongation During those growth process. existed cell wall must change to incorporate new material ,surface increasing and inducing water uptaking by protoplast Cell can extend 10. 100, even 1000 tomes of their original size but keeping same thickn
21、ess of cell wall So regulation of cell loosening is considered primary and important reaction of cell growth,Cell growth manner,Most plant cell grow by uniform deposition of cell wall materials where some of them demonstrate tip growth Plant cell possess array of cortical microtubes underlying and c
22、onnected to plasma membrane The orientation of microtubes array pridict cell wall structural materials especially cellulose deposition) will effects cell growth direction,Cell wall loosening mechanisms,The acid growth hypothesis postulated that auxin dependent acidification of cell wall promotes wal
23、l extensibility and cell growth,Cell wall loosening mechanisms,Enzymes for wall loosening activities 1.XET(xyloglucan endo-transglycoslase) 2.Expansin (with out in vitro hydrolic and trans-glycolytic activities) may do breakage of hydrogen bond.,Cell wall loosening mechanisms,In type I cell wall cel
24、l growth is associated with subtle biochemical change in pectin net work Cellulose and link glycan are embedded in pectin net works ,pectin must be control the access the enzymes to its substrates Newly synthesis of cell wall pectin are highly methylated ,when cell stop growth many methyl group were
25、 removed by desertification, with will facility Ca2+ bind to form rigid cell wall connection It was demonstrated meristimatic and elongation zone are less Ca 2+ and Ca2+ HGA junction,Cell wall loosening mechanisms,More obvious biochemical reaction occur in type II cell wall Along GAX were high subst
26、ituted by Ara and GlcA ,in maximum growth rate of coleoptiles ,those side chain not only preventing hydrogen bond between chains but also make those polymer water soluble while more and more nonsidechain GAX was found in stop growing cell Some type II cell in grass cells they accumulate mixed b-gluc
27、ans,Mixed b-glucan regulate cell growth,Relocked the structural polymer when cell growth ceased,for type I One locking component cell wall is extensions such as HRGPs in which the flexible region of those proteins will wrap around cellulose microfibrils . And rod like part will sever as spacer .betw
28、een extension may covalently bind to each other For type II cell wall threonine rich proteins(TRP) will take the place of HRGP and crossing lined phonetic compound will also take role in fix the cell wall form.,Cell wall and cell differentiation,Fruit ripening involves developmentally regulated chan
29、ges in cell wall architecture Secondary cell wall are elaborated after primary cell wall has stopped Acumulating suberin and cutin Lignin become major component in some cells secondary wall Some secondary wall can serve as storage materials,Suberin (萨布林 ),accumulation of Cutin to form cuticle,Lignin
30、,Storage materials,Cotyledon and endosperm of developing seeds containing little or no cellulose ,but single chain polysaccharide found in primary wall Function as strong wall to protect embryo or impose mechanical dormancy ,and storage carbohydrate for germination,Cell wall utilization by human bei
31、ng,As food (AGP,(arabionoglacto protein ) and pectin) Feed fungi and bacteria hydrolates as amino food ,sugar for bioethanol and other fine chemicals Fibrils, paper industry ,textiles,Cell wall modification,Environmental adaptation Mutation Genetic engineering,Assignment,Strategy plant genetic engin
32、eering for biofuel. Thanks for your patience !,Reference for assignment,1.Yuan JS, Tiller KH, Al-Ahmad H, Stewart NR, Stewart CN Jr. Trends Plant Sci. 2008 Aug;13(8):421-9. Epub 2008 Jul 16. Review. 2.Taylor LE 2nd, Dai Z, Decker SR, Brunecky R, Adney WS, Ding SY, Himmel ME. Trends Biotechnol. 2008 Aug;26(8):413-24. Epub 2008 Jun 23. Review. 3.Sticklen MB. Nat Rev Genet. 2008 Jun;9(6):433-43. Review. 4. Li X, Weng JK, Chapple C. Plant J. 2008 May;54(4):569-81. 5.Erratum in: Science. 2007 May 18;316(5813):804,Thanks for your patience !,