title: Populus GT43 family members group into distinct sets required for primary and secondary wall xylan biosynthesis and include useful promoters for wood modification.
abstract: The plant GT43 protein family includes xylosyltransferases that are known to be required for xylan backbone biosynthesis, but have incompletely understood specificities. RT-qPCR and histochemical (GUS) analyses of expression patterns of GT43 members in hybrid aspen, reported here, revealed that three clades of the family have markedly differing specificity towards secondary wall-forming cells (wood and extraxylary fibres). Intriguingly, GT43A and B genes (corresponding to the Arabidopsis IRX9 clade) showed higher specificity for secondary-walled cells than GT43C and D genes (IRX14 clade), although both IRX9 and IRX14 are required for xylosyltransferase activity. The remaining genes, GT43E, F and G (IRX9-L clade), showed broad expression patterns. Transient transactivation analyses of GT43A and B reporters demonstrated that they are activated by PtxtMYB021 and PNAC085 (master secondary wall switches), mediated in PtxtMYB021 activation by an AC element. The high observed secondary cell wall specificity of GT43B expression prompted tests of the efficiency of its promoter (pGT43B), relative to the CaMV 35S (35S) promoter, for overexpressing a xylan acetyl esterase (CE5) or downregulating REDUCED WALL ACETYLATION (RWA) family genes and thus engineering wood acetylation. CE5 expression was weaker when driven by pGT43B, but it reduced wood acetyl content substantially more efficiently than the 35S promoter. RNAi silencing of the RWA family, which was ineffective using 35S, was achieved when using GT43B promoter. These results show the utility of the GT43B promoter for genetically engineering properties of wood and fibres.
authors.affiliation: Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences (SLU), Umeå, Sweden.
authors.forename: Christine
authors.initials: C
authors.lastname: Ratke
authors.forename: Prashant Mohan-Anupama
authors.initials: PM
authors.lastname: Pawar
authors.forename: Vimal K
authors.initials: VK
authors.lastname: Balasubramanian
authors.forename: Marcel
authors.initials: M
authors.lastname: Naumann
authors.forename: Mathilda Lönnäs
authors.initials: ML
authors.lastname: Duncranz
authors.forename: Marta
authors.initials: M
authors.lastname: Derba-Maceluch
authors.forename: András
authors.initials: A
authors.lastname: Gorzsás
authors.forename: Satoshi
authors.initials: S
authors.lastname: Endo
authors.forename: Ines
authors.initials: I
authors.lastname: Ezcurra
authors.forename: Ewa J
authors.initials: EJ
authors.lastname: Mellerowicz
mesh_terms: D002473:Cell Wall / Q000378:metabolism*; D003001:Cloning, Molecular; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005822:Genetic Vectors / Q000378:metabolism; D005966:Glucuronidase / Q000378:metabolism; D005810:Multigene Family; D030821:Plants, Genetically Modified; D032107:Populus / Q000235:genetics*; D011401:Promoter Regions, Genetic; D015533:Transcriptional Activation / Q000235:genetics; D014934:Wood / Q000235:genetics / Q000378:metabolism*; D014990:Xylans / Q000096:biosynthesis*
chemical_list: D014990:Xylans; D005966:Glucuronidase
keywords: genetic engineering; poplar; secondary wall; transgenic trees; wood development; xylan biosynthesis