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Original Research ARTICLE

Front. Plant Sci., 10 April 2013 | http://dx.doi.org/10.3389/fpls.2013.00083

Three novel rice genes closely related to the Arabidopsis IRX9, IRX9L, and IRX14 genes and their roles in xylan biosynthesis

Dawn Chiniquy1,2, Patanjali Varanasi2,3,4, Taeyun Oh1, Jesper Harholt5, Jacob Katnelson2, Seema Singh2,3,4, Manfred Auer2,6, Blake Simmons2,3,4, Paul D. Adams2, Henrik V. Scheller2,4,7 and Pamela C. Ronald1,2,8*
  • 1Department of Plant Pathology, The Genome Center, University of California, Davis, CA, USA
  • 2Joint BioEnergy Institute, Emeryville, CA, USA
  • 3Sandia National Labs, Livermore, CA, USA
  • 4Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
  • 5Section for Plant Glycobiology, Department of Plant and Environmental Sciences, VKR Research Centre Pro-Active Plants, University of Copenhagen, Frederiksberg C, Denmark
  • 6Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
  • 7Department of Plant and Microbial Biology, University of California, Berkeley, CA, USA
  • 8Department of Plant Molecular Systems Biotechnology and Crop Biotech Institute, Kyung Hee University, Yongin, Korea

Xylan is the second most abundant polysaccharide on Earth, and represents a major component of both dicot wood and the cell walls of grasses. Much knowledge has been gained from studies of xylan biosynthesis in the model plant, Arabidopsis. In particular, the irregular xylem (irx) mutants, named for their collapsed xylem cells, have been essential in gaining a greater understanding of the genes involved in xylan biosynthesis. In contrast, xylan biosynthesis in grass cell walls is poorly understood. We identified three rice genes Os07g49370 (OsIRX9), Os01g48440 (OsIRX9L), and Os06g47340 (OsIRX14), from glycosyltransferase family 43 as putative orthologs to the putative β-1,4-xylan backbone elongating Arabidopsis IRX9, IRX9L, and IRX14 genes, respectively. We demonstrate that the over-expression of the closely related rice genes, in full or partly complement the two well-characterized Arabidopsis irregular xylem (irx) mutants: irx9 and irx14. Complementation was assessed by measuring dwarfed phenotypes, irregular xylem cells in stem cross sections, xylose content of stems, xylosyltransferase (XylT) activity of stems, and stem strength. The expression of OsIRX9 in the irx9 mutant resulted in XylT activity of stems that was over double that of wild type plants, and the stem strength of this line increased to 124% above that of wild type. Taken together, our results suggest that OsIRX9/OsIRX9L, and OsIRX14, have similar functions to the Arabidopsis IRX9 and IRX14 genes, respectively. Furthermore, our expression data indicate that OsIRX9 and OsIRX9L may function in building the xylan backbone in the secondary and primary cell walls, respectively. Our results provide insight into xylan biosynthesis in rice and how expression of a xylan synthesis gene may be modified to increase stem strength.

Keywords: xylan, irregular xylan mutants, cell walls, type II cell walls, xylosyltransferase

Citation: Chiniquy D, Varanasi P, Oh T, Harholt J, Katnelson J, Singh S, Auer M, Simmons B, Adams PD, Scheller HV and Ronald PC (2013) Three novel rice genes closely related to the Arabidopsis IRX9, IRX9L, and IRX14 genes and their roles in xylan biosynthesis. Front. Plant Sci. 4:83. doi: 10.3389/fpls.2013.00083

Received: 16 November 2012; Accepted: 21 March 2013;
Published online: 10 April 2013.

Edited by:

Frikkie C. Botha, BSES Limited, Australia

Reviewed by:

Geoff Fincher, University of Adelaide, Australia
William York, Unversity of Georgia, USA

Copyright: © 2013 Chiniquy, Varanasi, Oh, Harholt, Katnelson, Singh, Auer, Simmons, Adams, Scheller and Ronald. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.

*Correspondence: Pamela C. Ronald, Department of Plant Pathology, University of California – Davis, One Shields Avenue, Davis, CA 95616, USA. e-mail: pcronald@ucdavis.edu

Present address: Dawn Chiniquy, Energy Biosciences Institute, University of California, Berkeley, CA, USA.