Comprehensive Summary An efficient synthesis of a complex tetrasaccharide fragment 1 structurally related to rhamnogalacturonan ll side chain A has been accomplished through a stepwise glycosylation strategy.Challenge...Comprehensive Summary An efficient synthesis of a complex tetrasaccharide fragment 1 structurally related to rhamnogalacturonan ll side chain A has been accomplished through a stepwise glycosylation strategy.Challenges involved in the synthesis include the facile construction of the sterically crowded L-fucopyranose core and the stereoselective formation of two 1,2-cis-glycosidic linkages.The 3,4-disubstituted L-fucopyranoside structure was successfully constructed through a'counterclockwise'glycosylation sequence,namely,the less reactive axial 4-OH group of the central fucose unit was glycosylated first,then the 3-OH.Besides,a 2-pyridinecarbonyl-assistedα-D-xylosylation was developed to synthesize theα-D-xylopyranosidic linkage and a 3,4-O-benzoyl-controlledα-L-galactosylation reaction was usedforthe stereoselective synthesis of the correspondingα-L-galactopyranosidic linkage.展开更多
An aqueous acidic polysaccharide, named rhamnogalacturonan (designated as TTP-D2) was isolated from Tribulus terrestris L by means of DEAE-cellulose chromatography and gel filtration. The molecular mass of TTP-D2 was ...An aqueous acidic polysaccharide, named rhamnogalacturonan (designated as TTP-D2) was isolated from Tribulus terrestris L by means of DEAE-cellulose chromatography and gel filtration. The molecular mass of TTP-D2 was estimated to be 26 KDa by gel filtration. TTP-D2 is composed of galacturonic acid, rhamnose, arabinose, galactose, fucose, mannose, xylose and glucose in a ratio of 71.4 : 13.5 : 5.6 : 4.9 : 3.1 : 1.9 : 1.9 : 1.0. The main chain structure of TTP-D2 was elucidated as an acidic hetero-polysaccharide with the connection of a-(1-4) galacturonic acid with a-(1-3) rhamnose by GC analysis of partially hydrolyzed products and the determination of 1H, 13C-NMR spectra.展开更多
A series of nucleotide sugar interconversion enzymes(NSEs) generate the activated sugar donors required for biosynthesis of cell wall matrix polysaccharides and glycoproteins. UDPglucose 4-epimerases(UGEs) are NSEs th...A series of nucleotide sugar interconversion enzymes(NSEs) generate the activated sugar donors required for biosynthesis of cell wall matrix polysaccharides and glycoproteins. UDPglucose 4-epimerases(UGEs) are NSEs that function in the interconversion of UDP-glucose(UDP-Glc) and UDP-galactose(UDP-Gal). The roles of UDP-glucose 4-epimerases in monocots remain unclear due to redundancy in the pathways. Here, we report a brittle plant(bp1) rice mutant that exhibits brittle leaves and culms at all growth stages. The mutant culms had reduced levels of rhamnogalacturonan I, homogalacturonan, and arabinogalactan proteins.Moreover, the mutant had altered contents of uronic acids, neutral noncellulosic monosaccharides, and cellulose. Map-based cloning demonstrated that OsBP1 encodes a UDPglucose 4-epimerase(OsUGE2), a cytosolic protein. We also show that BP1 can form homoand hetero-protein complexes with other UGE family members and with UDP-galactose transporters 2(OsUGT2) and 3(OsUGT3), which may facilitate the channeling of Gal to polysaccharides and proteoglycans. Our results demonstrate that BP1 participates in regulating the sugar composition and structure of rice cell walls.展开更多
基金We appreciatethe National Natural Science Foundation of China(Nos.21921002,22177082)the Ministry of Science and Technology of China(2017ZX09101003-005-004)for financial support.
文摘Comprehensive Summary An efficient synthesis of a complex tetrasaccharide fragment 1 structurally related to rhamnogalacturonan ll side chain A has been accomplished through a stepwise glycosylation strategy.Challenges involved in the synthesis include the facile construction of the sterically crowded L-fucopyranose core and the stereoselective formation of two 1,2-cis-glycosidic linkages.The 3,4-disubstituted L-fucopyranoside structure was successfully constructed through a'counterclockwise'glycosylation sequence,namely,the less reactive axial 4-OH group of the central fucose unit was glycosylated first,then the 3-OH.Besides,a 2-pyridinecarbonyl-assistedα-D-xylosylation was developed to synthesize theα-D-xylopyranosidic linkage and a 3,4-O-benzoyl-controlledα-L-galactosylation reaction was usedforthe stereoselective synthesis of the correspondingα-L-galactopyranosidic linkage.
文摘An aqueous acidic polysaccharide, named rhamnogalacturonan (designated as TTP-D2) was isolated from Tribulus terrestris L by means of DEAE-cellulose chromatography and gel filtration. The molecular mass of TTP-D2 was estimated to be 26 KDa by gel filtration. TTP-D2 is composed of galacturonic acid, rhamnose, arabinose, galactose, fucose, mannose, xylose and glucose in a ratio of 71.4 : 13.5 : 5.6 : 4.9 : 3.1 : 1.9 : 1.9 : 1.0. The main chain structure of TTP-D2 was elucidated as an acidic hetero-polysaccharide with the connection of a-(1-4) galacturonic acid with a-(1-3) rhamnose by GC analysis of partially hydrolyzed products and the determination of 1H, 13C-NMR spectra.
基金This work was supported by the Key Laboratory of Biology,Genetics and Breeding of Japonica Rice in the Mid-lower Yangtze River,Ministry of Agriculture,ChinaJiangsu Plant Gene Engineering Research Center+4 种基金Jiangsu Collaborative Innovation Center for Modern Crop Productionsupported by grants from the National Key R&D Program of China(2016YFD0101107)Jiangsu Science and Technology Development Program(BE2017368)Jiangsu Agricultural Science and Technology Innovation Fund Project(CX(16)1029)the Fundamental Research Funds for the Central Universities(KYTZ201601)。
文摘A series of nucleotide sugar interconversion enzymes(NSEs) generate the activated sugar donors required for biosynthesis of cell wall matrix polysaccharides and glycoproteins. UDPglucose 4-epimerases(UGEs) are NSEs that function in the interconversion of UDP-glucose(UDP-Glc) and UDP-galactose(UDP-Gal). The roles of UDP-glucose 4-epimerases in monocots remain unclear due to redundancy in the pathways. Here, we report a brittle plant(bp1) rice mutant that exhibits brittle leaves and culms at all growth stages. The mutant culms had reduced levels of rhamnogalacturonan I, homogalacturonan, and arabinogalactan proteins.Moreover, the mutant had altered contents of uronic acids, neutral noncellulosic monosaccharides, and cellulose. Map-based cloning demonstrated that OsBP1 encodes a UDPglucose 4-epimerase(OsUGE2), a cytosolic protein. We also show that BP1 can form homoand hetero-protein complexes with other UGE family members and with UDP-galactose transporters 2(OsUGT2) and 3(OsUGT3), which may facilitate the channeling of Gal to polysaccharides and proteoglycans. Our results demonstrate that BP1 participates in regulating the sugar composition and structure of rice cell walls.
