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1Latest Papers from Table of Contents or Articles in PressAung, K. L., Fischer, S. E., Denroche, R. E., Jang, G.-H., Dodd, A., Creighton, S., Southwood, B., Liang, S.-B., Chadwick, D., Zhang, A., O'Kane, G. M., Albaba, H., Moura, S., Grant, R. C., Miller, J. K., Mbabaali, F., Pasternack, D., Lungu, I. M., Bartlett, J. M. S., Ghai, S., Lemire, M., Holter, S., Connor, A. A., Moffitt, R. A., Yeh, J. J., Timms, L., Krzyzanowski, P. M., Dhani, N., Hedley, D., Notta, F., Wilson, J. M., Moore, M. J., Gallinger, S., Knox, J. J.
The American Association for Cancer Research (AACR)
Published 2018Staff ViewPublication Date: 2018-03-16Publisher: The American Association for Cancer Research (AACR)Print ISSN: 1078-0432Electronic ISSN: 1557-3265Topics: MedicinePublished by: -
2Latest Papers from Table of Contents or Articles in PressSaori Sakabe, Brian M. Sullivan, Jessica N. Hartnett, Refugio Robles-Sikisaka, Karthik Gangavarapu, Beatrice Cubitt, Brian C. Ware, Dylan Kotliar, Luis M. Branco, Augustine Goba, Mambu Momoh, John Demby Sandi, Lansana Kanneh, Donald S. Grant, Robert F. Garry, Kristian G. Andersen, Juan Carlos de la Torre, Pardis C. Sabeti, John S. Schieffelin, Michael B. A. Oldstone
National Academy of Sciences
Published 2018Staff ViewPublication Date: 2018-08-08Publisher: National Academy of SciencesPrint ISSN: 0027-8424Electronic ISSN: 1091-6490Topics: BiologyMedicineNatural Sciences in GeneralPublished by: -
3Latest Papers from Table of Contents or Articles in PressC. Rotimi ; A. Abayomi ; A. Abimiku ; V. M. Adabayeri ; C. Adebamowo ; E. Adebiyi ; A. D. Ademola ; A. Adeyemo ; D. Adu ; D. Affolabi ; G. Agongo ; S. Ajayi ; S. Akarolo-Anthony ; R. Akinyemi ; A. Akpalu ; M. Alberts ; O. Alonso Betancourt ; A. M. Alzohairy ; G. Ameni ; O. Amodu ; G. Anabwani ; K. Andersen ; F. Arogundade ; O. Arulogun ; D. Asogun ; R. Bakare ; N. Balde ; M. L. Baniecki ; C. Beiswanger ; A. Benkahla ; L. Bethke ; M. Boehnke ; V. Boima ; J. Brandful ; A. I. Brooks ; F. C. Brosius ; C. Brown ; B. Bucheton ; D. T. Burke ; B. G. Burnett ; S. Carrington-Lawrence ; N. Carstens ; J. Chisi ; A. Christoffels ; R. Cooper ; H. Cordell ; N. Crowther ; T. Croxton ; J. de Vries ; L. Derr ; P. Donkor ; S. Doumbia ; A. Duncanson ; I. Ekem ; A. El Sayed ; M. E. Engel ; J. C. Enyaru ; D. Everett ; F. M. Fadlelmola ; E. Fakunle ; K. H. Fischbeck ; A. Fischer ; O. Folarin ; J. Gamieldien ; R. F. Garry ; S. Gaseitsiwe ; R. Gbadegesin ; A. Ghansah ; M. Giovanni ; P. Goesbeck ; F. X. Gomez-Olive ; D. S. Grant ; R. Grewal ; M. Guyer ; N. A. Hanchard ; C. T. Happi ; S. Hazelhurst ; B. J. Hennig ; C. Hertz ; Fowler ; W. Hide ; F. Hilderbrandt ; C. Hugo-Hamman ; M. E. Ibrahim ; R. James ; Y. Jaufeerally-Fakim ; C. Jenkins ; U. Jentsch ; P. P. Jiang ; M. Joloba ; V. Jongeneel ; F. Joubert ; M. Kader ; K. Kahn ; P. Kaleebu ; S. H. Kapiga ; S. K. Kassim ; I. Kasvosve ; J. Kayondo ; B. Keavney ; A. Kekitiinwa ; S. H. Khan ; P. Kimmel ; M. C. King ; R. Kleta ; M. Koffi ; J. Kopp ; M. Kretzler ; J. Kumuthini ; S. Kyobe ; C. Kyobutungi ; D. T. Lackland ; K. A. Lacourciere ; G. Landoure ; R. Lawlor ; T. Lehner ; M. Lesosky ; N. Levitt ; K. Littler ; Z. Lombard ; J. F. Loring ; S. Lyantagaye ; A. Macleod ; E. B. Madden ; C. R. Mahomva ; J. Makani ; M. Mamven ; M. Marape ; G. Mardon ; P. Marshall ; D. P. Martin ; D. Masiga ; R. Mason ; M. Mate-Kole ; E. Matovu ; M. Mayige ; B. M. Mayosi ; J. C. Mbanya ; S. A. McCurdy ; M. I. McCarthy ; H. McIlleron ; S. O. Mc'Ligeyo ; C. Merle ; A. O. Mocumbi ; C. Mondo ; J. V. Moran ; A. Motala ; M. Moxey-Mims ; W. S. Mpoloka ; C. L. Msefula ; T. Mthiyane ; N. Mulder ; G. Mulugeta ; D. Mumba ; J. Musuku ; M. Nagdee ; O. Nash ; D. Ndiaye ; A. Q. Nguyen ; M. Nicol ; O. Nkomazana ; S. Norris ; B. Nsangi ; A. Nyarko ; M. Nyirenda ; E. Obe ; R. Obiakor ; A. Oduro ; S. F. Ofori-Acquah ; O. Ogah ; S. Ogendo ; K. Ohene-Frempong ; A. Ojo ; T. Olanrewaju ; J. Oli ; C. Osafo ; O. Ouwe Missi Oukem-Boyer ; B. Ovbiagele ; A. Owen ; M. O. Owolabi ; L. Owolabi ; E. Owusu-Dabo ; G. Pare ; R. Parekh ; H. G. Patterton ; M. B. Penno ; J. Peterson ; R. Pieper ; J. Plange-Rhule ; M. Pollak ; J. Puzak ; R. S. Ramesar ; M. Ramsay ; R. Rasooly ; S. Reddy ; P. C. Sabeti ; K. Sagoe ; T. Salako ; O. Samassekou ; M. S. Sandhu ; O. Sankoh ; F. S. Sarfo ; M. Sarr ; G. Shaboodien ; I. Sidibe ; G. Simo ; M. Simuunza ; L. Smeeth ; E. Sobngwi ; H. Soodyall ; H. Sorgho ; O. Sow Bah ; S. Srinivasan ; D. J. Stein ; E. S. Susser ; C. Swanepoel ; G. Tangwa ; A. Tareila ; O. Tastan Bishop ; B. Tayo ; N. Tiffin ; H. Tinto ; E. Tobin ; S. M. Tollman ; M. Traore ; M. J. Treadwell ; J. Troyer ; M. Tsimako-Johnstone ; V. Tukei ; I. Ulasi ; N. Ulenga ; B. van Rooyen ; A. P. Wachinou ; S. P. Waddy ; A. Wade ; M. Wayengera ; J. Whitworth ; L. Wideroff ; C. A. Winkler ; S. Winnicki ; A. Wonkam ; M. Yewondwos ; T. sen ; N. Yozwiak ; H. Zar
American Association for the Advancement of Science (AAAS)
Published 2014Staff ViewPublication Date: 2014-06-21Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsKeywords: Africa ; Disease/*genetics ; England ; Genetics, Medical/trends ; Genome-Wide Association Study/*trends ; Genomics/*trends ; Health ; Humans ; National Institutes of Health (U.S.) ; United StatesPublished by: -
4Latest Papers from Table of Contents or Articles in PressS. K. Gire ; A. Goba ; K. G. Andersen ; R. S. Sealfon ; D. J. Park ; L. Kanneh ; S. Jalloh ; M. Momoh ; M. Fullah ; G. Dudas ; S. Wohl ; L. M. Moses ; N. L. Yozwiak ; S. Winnicki ; C. B. Matranga ; C. M. Malboeuf ; J. Qu ; A. D. Gladden ; S. F. Schaffner ; X. Yang ; P. P. Jiang ; M. Nekoui ; A. Colubri ; M. R. Coomber ; M. Fonnie ; A. Moigboi ; M. Gbakie ; F. K. Kamara ; V. Tucker ; E. Konuwa ; S. Saffa ; J. Sellu ; A. A. Jalloh ; A. Kovoma ; J. Koninga ; I. Mustapha ; K. Kargbo ; M. Foday ; M. Yillah ; F. Kanneh ; W. Robert ; J. L. Massally ; S. B. Chapman ; J. Bochicchio ; C. Murphy ; C. Nusbaum ; S. Young ; B. W. Birren ; D. S. Grant ; J. S. Scheiffelin ; E. S. Lander ; C. Happi ; S. M. Gevao ; A. Gnirke ; A. Rambaut ; R. F. Garry ; S. H. Khan ; P. C. Sabeti
American Association for the Advancement of Science (AAAS)
Published 2014Staff ViewPublication Date: 2014-09-13Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsKeywords: Base Sequence ; *Disease Outbreaks ; Ebolavirus/*genetics/isolation & purification ; *Epidemiological Monitoring ; Genetic Variation ; Genome, Viral/genetics ; Genomics/methods ; Hemorrhagic Fever, Ebola/epidemiology/*transmission/*virology ; Humans ; Mutation ; Sequence Analysis, DNA ; Sierra Leone/epidemiologyPublished by: -
5Latest Papers from Table of Contents or Articles in PressA. Aghakouchak ; D. Feldman ; M. J. Stewardson ; J. D. Saphores ; S. Grant ; B. Sanders
American Association for the Advancement of Science (AAAS)
Published 2014Staff ViewPublication Date: 2014-03-29Publisher: American Association for the Advancement of Science (AAAS)Print ISSN: 0036-8075Electronic ISSN: 1095-9203Topics: BiologyChemistry and PharmacologyComputer ScienceMedicineNatural Sciences in GeneralPhysicsKeywords: Agricultural Irrigation ; Animals ; Australia ; California ; Commerce ; Crops, Agricultural ; *Disasters ; *Droughts ; Humans ; Livestock ; Water Supply/economicsPublished by: -
6Articles: DFG German National LicensesStaff View
ISSN: 1467-923XSource: Blackwell Publishing Journal Backfiles 1879-2005Topics: Political ScienceType of Medium: Electronic ResourceURL: -
7Articles: DFG German National LicensesWYLLIE, S. GRANT ; BROPHY, JOSEPH J. ; SARAFIS, VASSILIOS ; HOBBS, MICHAEL
Oxford, UK : Blackwell Publishing Ltd
Published 1990Staff ViewISSN: 1750-3841Source: Blackwell Publishing Journal Backfiles 1879-2005Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, NutritionProcess Engineering, Biotechnology, Nutrition TechnologyNotes: The volatile components from the fruit of the Pistacia lentiscus tree were analyzed by capillary gas chromatography (CGC) and CGC-mass spectrometry. The major components were the monoterpenes α-pinene, β-pinene, myrcene and limonene. Several sesquiterpenes, aliphatic esters, ketones, and phenolic compounds such as thymol and carvacrol were also identified.Type of Medium: Electronic ResourceURL: -
8Articles: DFG German National LicensesBULLER, DAVID C. ; PARKER, WILLIAM ; REID, J. S. GRANT
[s.l.] : Nature Publishing Group
Published 1976Staff ViewISSN: 1476-4687Source: Nature Archives 1869 - 2009Topics: BiologyChemistry and PharmacologyMedicineNatural Sciences in GeneralPhysicsNotes: [Auszug] Embryo-free half seeds were prepared6 from husked barley (cultivar Ymer) and GA-induced starch hydrolysis was assayed by measuring7,8 the amount of reducing sugar released into the medium (1.05ml) by pairs of half endosperms incubated in the presence and absence of GA (80% GA3 20% GA1; 7.2 x 10?7 ...Type of Medium: Electronic ResourceURL: -
9Articles: DFG German National LicensesStaff View
ISSN: 0010-7565Topics: General, InterdisciplinaryURL: -
10Articles: DFG German National LicensesStaff View
ISSN: 0010-7565Topics: General, InterdisciplinaryURL: -
11Articles: DFG German National LicensesStaff View
ISSN: 0010-7565Topics: General, InterdisciplinaryURL: -
12Articles: DFG German National LicensesBuckeridge, Marcos S. ; Rocha, Dalva C. ; Reid, J. S. Grant ; Dietrich, Sonia M. C.
Oxford, UK : Blackwell Publishing Ltd
Published 1992Staff ViewISSN: 1399-3054Source: Blackwell Publishing Journal Backfiles 1879-2005Topics: BiologyNotes: The cotyledons of Copaifera langsdorfii Desf, have been shown to contain a water-soluble xyloglucan (amyloid), which represents about 40% of the seed's dry weight. On acid hydrolysis its composition (Glc:Xyl:Gal = 4.0:2.8–2.9:1.5–1.7) was similar to that of the well-characterized xyloglucan of Tamarindus indica L. (Glc:Xyl:Gal = 4.0:3.0–3.1:1.4). On hydrolysis with pure Trichoderma viride cellulase, both C. langsdorfii and T. indica xyloglucan gave the same xyloglucan oligosaccharides:〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00319317:PPL145:PPL_145_mu1"/〉but in significantly different proportions A:B1:B2:C = 1:0.4–0.5:2.1–2.2:3.1–3.4 in T. indica, and 1:1.1:1.8:7.4 and 1:1.3:2.6:12 for C. langsdorfii, savanna and forest populations respectively. This demonstrated a difference in fine molecular structure, notably in the distribution of the terminal non-reducing galactose substituents, between the xyloglucans of the two species and indicated differences in the specificities of their biosynthetic mechanisms. The xyloglucans obtained from C. langsdorfii seeds harvested from savanna and forest environments were slightly different, one from the other, in their sugar-residue composition (Glc:Xyl:Gal = 4.0:2.9:1.5 and 4.0:2.8:1.7, respectively), and were significantly different in the relative proportions of the xyloglucan oligosaccharides released on cellulase hydrolysis (above). Using light microscopy and biochemical methods, no difference in the pattern or rate of postgerminative xyloglucan metabolism was detected in seeds of savanna and forest origin. This is the first clear experimental evidence for differences in a storage xyloglucan structure between populations of the same species. It may indicate environmental influences on xyloglucan biosynthesis.Type of Medium: Electronic ResourceURL: -
13Articles: DFG German National LicensesARMSTRONG, SHARYN G. ; LEACH, DAVID N. ; WYLLIE, S. GRANT
Oxford, UK : Blackwell Publishing Ltd
Published 1991Staff ViewISSN: 1750-3841Source: Blackwell Publishing Journal Backfiles 1879-2005Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, NutritionProcess Engineering, Biotechnology, Nutrition TechnologyNotes: Fatty acid compositions and lipid levels of five common table varieties of marine fish from temperate Australian waters were determined. Nutritionally important values were calculated and compared with those of species from similar waters in the northern hemisphere. P/S and n-3/n-6 ratios, and the levels of arachidonic (AA) and docosahexaenoic (DHA) acids in the lipids were comparable for the two, but the Australian species had lower eicosapentaenoic acid (EPA) levels. Oils from Australian fish were shown to have nutritional properties as beneficial as their northern hemisphere counterparts.Type of Medium: Electronic ResourceURL: -
14Articles: DFG German National LicensesStaff View
ISSN: 1434-0879Keywords: Urinary tract infection ; Super-infection ; Anti-adherence factor ; Sialomucin layerSource: Springer Online Journal Archives 1860-2000Topics: MedicineNotes: Summary Pre-existing bacteriuria of 2 to 3 weeks' duration in the rabbit had no effect on either the histological integrity of the sialomucin layer (anti-adherence factor) of the bladder mucosa or the protective effect of this layer against super-infection.Type of Medium: Electronic ResourceURL: -
15Articles: DFG German National LicensesStaff View
ISSN: 1432-2048Keywords: Alpha galactosidase ; Cell wall storage polysaccharide ; Cyamopsis ; Galactomannan (biosynthesis) ; Senna ; TrigonellaSource: Springer Online Journal Archives 1860-2000Topics: BiologyNotes: Abstract Galactomannan deposition was investigated in developing endosperms of three leguminous species representative of taxonomic groups which have galactomannans with high, medium and low galactose content. These were fenugreek (Trigonella foenum-graecum L.; mannose/galactose (Man/Gal) = 1.1), guar (Cyamopsis tetragonoloba (L.) Taub.; Man/Gal = 1.6) and Senna occidentalis (L.) Link. (Man/Gal = 3.3), respectively. Endosperms were analysed at different stages of seed development for galactomannan content and the levels, in cell-free extracts, of a mannosyltransferase and a galactosyltransferase which have been shown to catalyse galactomannan biosynthesis in vitro (M. Edwards et al., 1989, Planta 178, 41–51). There was a close correlation in each case between the levels of the biosynthetic mannosyl- and galactosyltransferases and the deposition of galactomannan. The relative in vitro activities of the mannosyl- and galactosyltransferases in fenugreek and guar were similar, and almost constant throughout the period of galactomannan deposition. In Senna the ratio mannosyltransferase/galactosyltransferase was always higher than in the other two species, and it increased substantially throughout the period of galactomannan deposition. In fenugreek and guar the galactomannans present in the endosperms of seeds at different stages of development had the Man/Gal ratios characteristic of the mature seeds. By contrast the galactomannan present in Senna endosperms at the earliest stages of deposition had a Man/Gal ratio of about 2.3. During late deposition this ratio increased rapidly, stabilising at about 3.3, the ratio characteristic of the mature seed. The levels of α-galactosidase in the developing endosperms of fenugreek and guar were low and remained fairly constant throughout the deposition of the galactomannan. In Senna, α-galactosidase activity in the endosperm was low during early galactomannan deposition, but increased subsequently, peaking during late galactomannan deposition. The developmental patterns of the α-galactosidase activity and of the increase in Man/Gal ratio of the Senna galactomannan were closely similar, indicating a cause-and-effect relationship. The endosperm α-galactosidase activity in Senna was capable, in vitro, of removing galactose from guar galactomannan without prior depolymerisation of the molecule. In fenugreek and in guar the genetic control of the Man/Gal ratio in galactomannan is not the result of a post-depositional modification, and must reside in the biosynthetic process. In Senna, the Man/Gal ratio of the primary biosynthetic galactomannan product is controlled by the biosynthetic process. Yet the final Man/Gal ratio of the galactomannan in the mature seed is, to an appreciable extent, the result of galactose removal from the primary biosynthetic product by an α-galactosidase activity which is present in the endosperm during late galactomannan deposition.Type of Medium: Electronic ResourceURL: -
16Articles: DFG German National LicensesStaff View
ISSN: 1432-2048Keywords: Galactomannan ; Endosperm ; Polysaccharide (biosynthesis, storage) ; Mannosyltransferase ; Seed (development) ; TrigonellaSource: Springer Online Journal Archives 1860-2000Topics: BiologyNotes: Abstract The time-course of galactomannan and stachyose (digalactosyl-sucrose) deposition in the fenugreek seed endosperm has been determined, and correlated with standard parameters of seed development. During, and only during, the period of galactomannan deposition, endosperm homogenates are capable of catalysing the transfer of labelled d-mannosyl residues from guanosine 5′-diphosphate d-[U-14C]mannose to a soluble polysaccharide product indistinguishable from galactomannan. The mannosyltransferase activity peaks twice, once at the beginning of galactomannan deposition, and again in the middle of the most rapid phase of galactomannan deposition. The enzyme in the later peak sediments with grossly particulate material (1,000 g pellet), whereas the earlier peak contains a considerable proportion of a particulate enzyme sedimenting at 100,000 g. These observations are discussed in the light of existing information on the ultrastructural aspects of galactomannan deposition. The mannosyltransferase is clearly involved in galactomannan formation in vivo, but the status of an accompanying galactosyltransferase is less clear.Type of Medium: Electronic ResourceURL: -
17Articles: DFG German National LicensesStaff View
ISSN: 1432-2048Keywords: Arabinan ; Arabinogalactan ; Cell wall (storage polysaccharides) ; Galactan ; Germination (seeds) ; Hemicellulose ; LupinusSource: Springer Online Journal Archives 1860-2000Topics: BiologyNotes: Abstract Some 22% of the dry weight of the cotyledons of resting seeds of Lupinus angustifolius cv. Unicrop has been shown to be non-starch polysaccharide material comprising the massively thickened walls of the storage mesophyll cells. On hydrolysis this material released galactose (76%), arabinose (13%), xylose (4%), uronic acid (7%): only traces of glucose were detected indicating the virtual absence of cellulose from the walls. Changes in the amount and composition of this material following germination have been studied in relation to parameters of seedling development and the mobilisation of protein, lipid and oligosaccharide reserves. Starch, which was not present in the resting seed, appeared transitorily following germination: under conditions of continuous darkness starch levels were reduced. During the period of bulk-reserve mobilisation, 92% of the non-starch polysaccharide material disappeared from the cotyledons. The residual cell-wall material released galactose (14%), arabinose (19%), xylose (24%) and uronic acid (43%). The galactose and arabinose residues of the cotyledonary cell walls clearly constitute a major storage material, quantitatively as important as protein. The overall role of the wall polysaccharides in seedling development is discussed.Type of Medium: Electronic ResourceURL: -
18Articles: DFG German National LicensesStaff View
ISSN: 1432-2048Keywords: Biosynthesis (computer simulation) ; Cell wall (plant) ; Cyamopsis ; Galactomannan ; Senna ; TrigonellaSource: Springer Online Journal Archives 1860-2000Topics: BiologyNotes: Abstract Membrane-bound enzymes from developing legume-seed endosperms catalyse galactomannan biosynthesis in vitro from GDP-mannose and UDP-galactose. A mannosyltransferase [mannan synthase] catalyses the extension of the linear (1→4)-β-linked d-mannan backbone towards the non-reducing end. A specific α-galactosyltransferase brings about the galactosyl-substitution of the backbone by catalysing the transfer of a (1→6)-α-d-galactosyl residue to an acceptor mannosyl residue at or close to the non-reducing terminus of the growing backbone. Labelled galactomannans with a range of mannose/galactose (Man/Gal) ratios were formed in vitro from GDP-[14C]mannose and UDP-[14C]galactose using membrane-bound enzyme preparations from fenugreek (Trigonella foenum-graecum L.), guar (Cyamopsis tetragonoloba (L.) Taub.) and senna (Senna occidentalis (L.) Link.), species which in vivo, form galactomannans with Man/Gal ratios of 1.1, 1.6 and 3.3 respectively. The labelled galactomannans were fragmented using a structure-sensitive endo-(1→4)-β-d-mannanase and the quantitative fragmentation data were processed using a computer algorithm which simulated the above model for galactomannan biosynthesis on the basis of a second-order Markov chain process, and also the subsequent action of the endo-mannanase. For each galactomannan data-set processed, the algorithm generated a set of four conditional probabilities required by the Markov model. The need for a second-order Markov chain description indicated that the galactomannan subsite recognition sequence of the galactosyltransferase must encompass at least three backbone mannose residues, i.e. the site of substitution and the two preceding ones towards the reducing end of the growing galactomannan chain. Data-sets from the three plant species generated three distinctly different sets of probabilities, and hence galactose-substitution rules. For each species, the maximum degree of galactose-substitution consistent with these rules was closely similar to that observed for the primary product of galactomannan biosynthesis in vivo. The data provide insight into the mechanism of action and the spatial organisation of membrane-bound polysaccharide synthases.Type of Medium: Electronic ResourceURL: -
19Articles: DFG German National LicensesStaff View
ISSN: 1432-2048Keywords: Amyloid (seed) ; Endo-β-glucanase ; β-Galactosidase ; Germination (seed) ; β-Glucosidase ; Tropaeolum (amyloid mobilisation) ; Xyloglucan ; α-XylosidaseSource: Springer Online Journal Archives 1860-2000Topics: BiologyNotes: Abstract The levels of cell-wall xyloglucan (amyloid) in nasturtium (Tropaeolum majus L.) cotyledons were monitored during a 28-d period covering seed imbibition, germination and early seedling development. The activities of the following enzymes capable of hydrolysing the glycosidic linkages in the xyloglucan were assayed in cotyledon extracts over the same period: endo-(1→4)-β-glucanase (EC 3.2.1.4), β-glucosidase (EC 3.2.1.21), α-xylosidase and β-galactosidase (EC 3.2.1.23). The endo-β-glucanase was assayed viscometrically using xyloglucan as substrate, and the three glycosidases using appropriate p-nitrophenylglycosides. Alpha xylosidase and β-galactosidase, the enzymes which would be expected to hydrolyse the side-chains from the xyloglucan molecule, were also assyed using xyloglucan as substrate. Under our culture conditions, xyloglucan levels remained constant at 30 mg per cotyledon pair for 7 d, that is until 3 d after germination: thereafter, the amount of xyloglucan diminished to zero in a 12-d period. The most rapid period of depletion was between days 9 and 13. The mobilisation of all reserve substances from the cotyledons resulted in a weight-loss of 92 mg: xyloglucan, therefore, is an important storage substance, representing 33% by weight of the seed's substrate reserves. It is a cell-wall storage polysaccharide. Xyloglucan mobilisation was accompanied by a 17-fold increase in endo-β-glucanase activity, a 7-fold increase in β-galactosidase and an 8-fold increase in α-xylosidase activities, all determined using xyloglucan as substrate. All three activities began to increase at day 5, peaked at days 12–14 when the most rapid phase of xyloglucan breakdown was over, and had declined to zero by days 22–25. The levels of theses enzymes have been shown to be consistent with their being responsible for xyloglucan hydrolysis in vivo. Nitrophenyl-β-galactosidase activity increased up to day 3, remained constant and then increased again 2.5-fold from day 5, peaking at day 11. Nitrophenyl-β-glucosidase remained relatively constant up to day 16 and then decreased to zero by day 25. Nitrophenyl-α-xylosidase activity was not detected.Type of Medium: Electronic ResourceURL: -
20Articles: DFG German National LicensesStaff View
ISSN: 1432-2048Keywords: Cell wall (plant) ; Enzyme (specificity) ; Hemicellulose ; Tropaeolum ; Xyloglucan ; Xyloglucanendo-transglycosylaseSource: Springer Online Journal Archives 1860-2000Topics: BiologyNotes: Abstract We have investigated the substrate subsite recognition requirement of the xyloglucan endo-transglycosylase/xyloglucan-specific endo-(1→4)-β-d-glucanase (NXET) from the cotyledons of nasturtium seedlings. Seed xyloglucans are composed almost entirely of the Glc4 subunits XXXG, XLXG, XXLG and XLLG, where G represents an unsubstituted glucose residue, X a xylose-substituted glucose residue and L a galactosyl-xylose-substituted glucose residue. Thus in the xyloglucan sequence shown below, the xylose (Xyl) residues at the backbone glucose (Glc) residues numbered — 3,— 2, + 2 and + 3 may be galactose-substituted, and NXET cleaves between the unsubstituted glucose at — 1 and the xylose-substituted glucose at + 1, which never carries a galactosyl substituent. We have isolated the xyloglucan oligosaccharides XXXGXXXG and XLLGXLLG from NXET digests of tamarind seed xyloglucan, have modified them enzymatically using a pure xyloglucan oligosaccharide-specific α-xylosidase from nasturtium seeds to give GXXGXXXG and GLLGXLLG, and have identified and compared the products of NXET action on XXXGXXXG, GXXGXXXG, XLLGXLLG and GLLGXLLG. We have also compared the molar proportions of XXXG, XLXG, XXLG and XLLG in native tamarind and nasturtium seed xyloglucans with those in NXET digests of these polysaccharides. Using these and existing data we have demonstrated that NXET action does not require xylosesubstitution at glucose residues — 4, — 2, + 1 and + 3 and that xylose substitution at + 2, is a requirement. There may also be a requirement for xylose substitution at — 3. We have demonstrated also that galactosyl substitution of a xylose residue at + 1 prevents, and at — 2 modifies, chain-cleavage. A partial model for the minimum substrate binding requirement of NXET is proposed.Type of Medium: Electronic ResourceURL: