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Title: UUAT1 Is a Golgi-Localized UDP-Uronic Acid Transporter That Modulates the Polysaccharide Composition of Arabidopsis Seed Mucilage

UDP-glucuronic acid (UDP-GlcA) is the precursor of many plant cell wall polysaccharides and is required for production of seed mucilage. Following synthesis in the cytosol, it is transported into the lumen of the Golgi apparatus, where it is converted to UDP-galacturonic acid (UDP-GalA), UDP-arabinose, and UDP-xylose. To identify the Golgi-localized UDP-GlcA transporter, we screened Arabidopsis thaliana mutants in genes coding for putative nucleotide sugar transporters for altered seed mucilage, a structure rich in the GalA-containing polysaccharide rhamnogalacturonan I. As a result, we identified UUAT1, which encodes a Golgi-localized protein that transports UDP-GlcA and UDP-GalA in vitro. The seed coat of uuat1 mutants had less GalA, rhamnose, and xylose in the soluble mucilage, and the distal cell walls had decreased arabinan content. Cell walls of other organs and cells had lower arabinose levels in roots and pollen tubes, but no differences were observed in GalA or xylose contents. Furthermore, the GlcA content of glucuronoxylan in the stem was not affected in the mutant. Interestingly, the degree of homogalacturonan methylation increased in uuat1. These results suggest that this UDP-GlcA transporter plays a key role defining the seed mucilage sugar composition and that its absence produces pleiotropic effects in this component of themore » plant extracellular matrix.« less
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  1. Univ. of Adres Bello, Santiago (Chile). Center for Plant Biotechnology
  2. Univ. of Melbourne (Australia). ARC Centre of Excellence in Plant Cell Walls
  3. Normandy Univ. (France)
  4. Univ. of Cambridge (United Kingdom). Dept. of Biochemistry
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Joit BioEnergy Inst. and Biological Systems and Engineering Division; Univ. of California, Berkeley, CA (United States). Dept. of Plant and Microbial Biology
  6. Univ. of Melbourne (Australia). ARC Centre of Excellence in Plant Cell Walls; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Joint BioEnergy Inst. and Biological Systems and Engineering Division
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Plant Cell
Additional Journal Information:
Journal Volume: 29; Journal Issue: 1; Journal ID: ISSN 1040-4651
American Society of Plant Biologists
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
OSTI Identifier: