细胞与分子生物学1

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1、ThePlantCellWallPart1•Cellwallstructure•PolysaccharidesinthewallPart2•CellwallbiosynthesisPart3•Cellwallproteins•Aromaticcompounds(incl.lignin)•Cross-linking•Cellexpansion•CellwalldegradationPhenolicsPhenolicsProteinProteinCelluloseCellulosePectinPectinHemicelluloseHemice

2、lluloseMostplantsGrassesFigure15.14Arepeatedhydroxyproline-richmotiffromamoleculeofHRGPfromtomatoHRGPFigure15.15AhighlybranchedarabinogalactanmoleculeArabinogalactan-proteins•AGPsare“proteoglycans”-morepolysaccharidethanprotein•Involvedincell-cellinteractionsanddifferenti

3、ation•50-100differentpolypeptidesinArabidopsis(eachmayhavedifferentlyglycosylatedforms)•ManyAGPsareGPIanchoredproteinsAGP(thisparticularstructureknownfromtobacco)GumArabicFigure13.7Outlineofphenolicbiosynthesisfromphenylalanineonward(Part1)Ferulic(andcoumaric)acidcanbeest

4、erlinkedtoarabinoseorgalactoseinpectin(Chenopodiaceae,e.g.spinachandsugarbeet)Ferulic(andcoumaric)acidesterlinkedtoarabinoxylanischaracteristicofgrasscellwallsGrass-arabinoxylanwithferulateesterOHOHOOHOHOOHOOHOOOOOOOOHOHOOHOOHOHOCH3HCOCOOH3H3COCOOHFerulicacidcanOCH3OHOdim

5、erizewhenHOHOoxidized.HCOCOOH3COOH5,5'-diferulicacid8-O-4'-diferulicacidThesedimerscanCOOHcross-linkHOCOOHHOCOOHCOOHarabinoxylanHCO3HCO3OOHOCH3OCH38.5'-Diferulicacid8,5'-DiferulicacidbenzofuranformHCOCOOH3HCOCOOHOH3HOCOOHHOHOOCOCH3OCH3OH8,8'-Diferulicacid8,5'-Diferulicaci

6、daryltetralinformSomecellsdevelopasecondarywallafterexpansionhasceasedFigure15.18SecondarycellwallsCompositionofthesecondarywallsThemainhemicelluloseisglucuronoxylaninallangiospermsFigure15.17PhenolicsubunitsoflignininfiltratethespacebetweencellulosemicrofibrilsLigninmake

7、sthewallsstrong,watertight,anddifficulttodegradeFigure15.18Secondarycellwalls;(C)MonolignolsthatmakeupH,G,andSligninFigure15.18Secondarycellwalls;(D)StructureofpoplarligninFigure15.18Secondarycellwalls;(D)StructureofpoplarligninEffectoflignincontentonsugarandbiomassyields

8、Saccharificationefficiency(totalsugarreleasedasapercentageoftotalsugarinthecellwallresidue)Chen,