Molecular Plant Advance Access originally published online on August 24, 2009
Molecular Plant 2009 2(5):1040-1050; doi:10.1093/mp/ssp068
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Two Poplar Glycosyltransferase Genes, PdGATL1.1 and PdGATL1.2, Are Functional Orthologs to PARVUS/AtGATL1 in Arabidopsis
a Complex Carbohydrate Research Center, The University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA
b BioEnergy Science Center, The University of Georgia, 315 Riverbend Road, Athens, GA 30602, USA
c Computational System Biology Lab, Dept. of Biochemistry and Molecular Biology, and Institute of Bioinformatics, The University of Georgia, Athens, GA 30602, USA
1 To whom correspondence should be addressed. E-mail hahn{at}ccrc.uga.edu, fax +01 706 542 4412, tel. +01 706 542 4457
Several genes in Arabidopsis, including PARVUS/AtGATL1, have been implicated in xylan synthesis. However, the biosynthesis of xylan in woody plants, where this polysaccharide is a major component of wood, is poorly understood. Here, we characterize two Populus genes, PdGATL1.1 and PdGATL1.2, the closest orthologs to the Arabidopsis PARVUS/GATL1 gene, with respect to their gene expression in poplar, their sub-cellular localization, and their ability to complement the parvus mutation in Arabidopsis. Overexpression of the two poplar genes in the parvus mutant rescued most of the defects caused by the parvus mutation, including morphological changes, collapsed xylem, and altered cell wall monosaccharide composition. Quantitative RT–PCR showed that PdGATL1.1 is expressed most strongly in developing xylem of poplar. In contrast, PdGATL1.2 is expressed much more uniformly in leaf, shoot tip, cortex, phloem, and xylem, and the transcript level of PdGATL1.2 is much lower than that of PdGATL1.1 in all tissues examined. Sub-cellular localization experiments showed that these two proteins are localized to both ER and Golgi in comparison with marker proteins resident to these sub-cellular compartments. Our data indicate that PdGATL1.1 and PdGATL1.2 are functional orthologs of PARVUS/GATL1 and can play a role in xylan synthesis, but may also have role(s) in the synthesis of other wall polymers.
Key Words: Arabidopsis thaliana • poplar • xylan • glycosyltransferase
2 These authors contributed equally to this work.
3 Current address: Qingdao Institute of Bioenergy and Bioprocess Technology, No.189 Songling Road, Laoshan District, Qingdao 266101, People's Republic of China.