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Golgi-localized putative S-adenosyl methionine transporters required for plant cell wall polysaccharide methylation.

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Phyo, Pyae 
Yang, Weibing 
Lyczakowski, Jan J 
Echevarría-Poza, Alberto 


Polysaccharide methylation, especially that of pectin, is a common and important feature of land plant cell walls. Polysaccharide methylation takes place in the Golgi apparatus and therefore relies on the import of S-adenosyl methionine (SAM) from the cytosol into the Golgi. However, so far, no Golgi SAM transporter has been identified in plants. Here we studied major facilitator superfamily members in Arabidopsis that we identified as putative Golgi SAM transporters (GoSAMTs). Knockout of the two most highly expressed GoSAMTs led to a strong reduction in Golgi-synthesized polysaccharide methylation. Furthermore, solid-state NMR experiments revealed that reduced methylation changed cell wall polysaccharide conformations, interactions and mobilities. Notably, NMR revealed the existence of pectin 'egg-box' structures in intact cell walls and showed that their formation is enhanced by reduced methyl esterification. These changes in wall architecture were linked to substantial growth and developmental phenotypes. In particular, anisotropic growth was strongly impaired in the double mutant. The identification of putative transporters involved in import of SAM into the Golgi lumen in plants provides new insights into the paramount importance of polysaccharide methylation for plant cell wall structure and function.



Arabidopsis, Arabidopsis Proteins, Cell Wall, Golgi Apparatus, Membrane Transport Proteins, Methionine, Methylation, Pectins, Polysaccharides

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Nat Plants

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Springer Science and Business Media LLC
Biotechnology and Biological Sciences Research Council (BB/L014130/1)
US Department of Energy (via Pennsylvania State University) (DE-SC0001090)
The characterisation of gosamt mutants was supported as part of The Center for Lignocellulose Structure and Formation, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under Award # DE-SC0001090. This study made use of NMR spectrometers at the MIT-Harvard Center for Magnetic Resonance, which is supported by NIH grant P41 GM132079. Initial gene identification, mutant isolation and preliminary pectin methylation studies were done by H.T. and P.D. under grant EPSRC/BBSRC OpenPlant (BB/L014130/1) and A.O., J.P.P-R and S.S-A supported by Fondo de Areas Prioritarias- Centro de Regulacion del Genoma-15090007, FONDECYT 1190695 and FONDECYT 1201467. Most of the microscopy experiments made use of The Sainsbury Laboratory Microscopy Core Facility which is supported by the Gatsby Charitable Foundation.
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