Oxford University Press (OUP)
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Transfer Specificity of Detergent-Solubilized Fenugreek Galactomannan Galactosyltransferase Abstract
The current experimental model for galactomannan biosynthesis in membrane-bound enzyme systems from developing legume-seed endosperms involves functional interaction between a GDP-mannose (Man) mannan synthase and a UDP-galactose (Gal) galactosyltransferase. The transfer specificity of the galactosyltransferase to the elongating mannan chain is critical in regulating the distribution and the degree of Gal substitution of the mannan backbone of the primary biosynthetic product. Detergent solubilization of the galactosyltransferase of fenugreek (Trigonella foenum-graecum) with retention of activity permitted the partial purification of the enzyme and the cloning and sequencing of the corresponding cDNA with proof of functional identity. We now document the positional specificity of transfer of (14C)Gal from UDP-(14C)Gal to manno-oligosaccharide acceptors, chain lengths 5 to 8, catalyzed by the detergent-solubilized galactosyltransferase. Enzymatic fragmentation analyses of the labeled products showed that a single Gal residue was transferred per acceptor molecule, that the linkage was (1→6)-α, and that there was transfer to alternative Man residues within the acceptor molecules. Analysis of the relative frequencies of transfer to alternative Man residues within acceptor oligosaccharides of different chain length allowed the deduction of the substrate subsite recognition requirement of the galactosyltransferase. The enzyme has a principal recognition sequence of six Man residues, with transfer of Gal to the third Man residue from the nonreducing end of the sequence. These observations are incorporated into a refined model for enzyme interaction in galactomannan biosynthesis.
Oxford University Press (OUP) - Tập 129 Số 3 - Trang 1391-1397 - 2002
Rapid Structural Phenotyping of Plant Cell Wall Mutants by Enzymatic Oligosaccharide Fingerprinting Abstract
Various biochemical, chemical, and microspectroscopic methods have been developed throughout the years for the screening and identification of mutants with altered cell wall structure. However, these procedures fail to provide the insight into structural aspects of the cell wall polymers. In this paper, we present various methods for rapidly screening Arabidopsis cell wall mutants. The enzymatic fingerprinting procedures using high-performance anion-exchange-pulsed-amperometric detection liquid chromatography, fluorophore-assisted carbohydrate electrophoresis, and matrix-assisted laser-desorption ionization time of flight (MALDI-TOF) mass spectrometry (MS) were exemplified by the structural analysis of the hemicellulose xyloglucan. All three techniques are able to identify structural alterations of wall xyloglucans in mur1,mur2, and mur3, which in comparison with the wild type have side chain defects in their xyloglucan structure. The quickest analysis was provided by MALDI-TOF MS. Although MALDI-TOF MS per se is not quantitative, it is possible to reproducibly obtain relative abundance information of the various oligosaccharides present in the extract. The lack of absolute quantitation by MALDI-TOF MS was compensated for with a xyloglucan-specific endoglucanase and simple colorimetric assay. In view of the potential for mass screening using MALDI-TOF MS, a PERL-based program was developed to process the spectra obtained from MALDI-TOF MS automatically. Outliers can be identified very rapidly according to a set of defined parameters based on data collected from the wild-type plants. The methods presented here can easily be adopted for the analysis of other wall polysaccharides. MALDI-TOF MS offers a powerful tool to screen and identify cell wall mutants rapidly and efficiently and, more importantly, is able to give initial insights into the structural composition and/or modification that occurs in these mutants.
Oxford University Press (OUP) - Tập 130 Số 4 - Trang 1754-1763 - 2002
Glycoside Hydrolases and Glycosyltransferases. Families, Modules, and Implications for Genomics
Oxford University Press (OUP) - Tập 124 Số 4 - Trang 1515-1519 - 2000
Incorporation of UDP-[<sup>14</sup>C]Glucose into Xyloglucan by Pea Membranes
Oxford University Press (OUP) - Tập 91 Số 1 - Trang 373-378 - 1989
Nutrient Influences on Leaf Photosynthesis
Oxford University Press (OUP) - Tập 65 Số 3 - Trang 541-543 - 1980
Stromal Acidification Mediates <i>In Vivo</i> Water Stress Inhibition of Nonstomatal-Controlled Photosynthesis
Oxford University Press (OUP) - Tập 72 Số 4 - Trang 1123-1126 - 1983
Conversion of Endogenous Indole-3-Butyric Acid to Indole-3-Acetic Acid Drives Cell Expansion in Arabidopsis Seedlings Abstract Genetic evidence in Arabidopsis (Arabidopsis thaliana) suggests that the auxin precursor indole-3-butyric acid (IBA) is converted into active indole-3-acetic acid (IAA) by peroxisomal β-oxidation; however, direct evidence that Arabidopsis converts IBA to IAA is lacking, and the role of IBA-derived IAA is not well understood. In this work, we directly demonstrated that Arabidopsis seedlings convert IBA to IAA. Moreover, we found that several IBA-resistant, IAA-sensitive mutants were deficient in IBA-to-IAA conversion, including the indole-3-butyric acid response1 (ibr1) ibr3 ibr10 triple mutant, which is defective in three enzymes likely to be directly involved in peroxisomal IBA β-oxidation. In addition to IBA-to-IAA conversion defects, the ibr1 ibr3 ibr10 triple mutant displayed shorter root hairs and smaller cotyledons than wild type; these cell expansion defects are suggestive of low IAA levels in certain tissues. Consistent with this possibility, we could rescue the ibr1 ibr3 ibr10 short-root-hair phenotype with exogenous auxin. A triple mutant defective in hydrolysis of IAA-amino acid conjugates, a second class of IAA precursor, displayed reduced hypocotyl elongation but normal cotyledon size and only slightly reduced root hair lengths. Our data suggest that IBA β-oxidation and IAA-amino acid conjugate hydrolysis provide auxin for partially distinct developmental processes and that IBA-derived IAA plays a major role in driving root hair and cotyledon cell expansion during seedling development.
Oxford University Press (OUP) - Tập 153 Số 4 - Trang 1577-1586 - 2010
Studies on Sequential Parasitism by <i>Orobanche</i> and <i>Cuscuta</i> on <i>Petunia hybrida</i>
Oxford University Press (OUP) - Tập 59 Số 1 - Trang 30-32 - 1977
Role of Polysaccharides in Diatom <i>Thalassiosira pseudonana</i> and its Associated Bacteria in Hydrocarbon Presence
Oxford University Press (OUP) - Tập 180 Số 4 - Trang 1898-1911 - 2019
Potassium Nutrition and Translocation in Sugar Beet
Oxford University Press (OUP) - Tập 70 Số 1 - Trang 168-172 - 1982
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