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PttMAP20, a novel microtubule-associated protein in the secondary cell walls of Populus tremula L. x tremuloides Michx. is a target of the cellulose synthesis inhibitor, 2,6-dichlorobenzonitrile |
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Rajangam AS, Kumar M, Aspeborg H, Guerreiro G, Arvestad L, Pansri P, Brown CJ-L, Hober S, Blomqvist K, Divne C, Ezcurra I, Mellerowicz E, Sundberg B, Bulone V, Teeri TT, 2008, PttMAP20, a novel microtubule-associated protein in the secondary cell walls of Populus tremula L. x tremuloides Michx. is a target of the cellulose synthesis inhibitor, 2,6-dichlorobenzonitrile. Plant Physiology 148: 1283-1294.
We have identified a gene, denoted PttMAP20, which is strongly up-regulated during secondary cell wall synthesis and tightlycoregulated with the secondary wall-associated CESA genes in hybrid aspen (Populus tremula 3 tremuloides). Immunolocalizationstudies with affinity-purified antibodies specific for PttMAP20 revealed that the protein is found in all cell types indeveloping xylem and that it is most abundant in cells forming secondary cell walls. This PttMAP20 protein sequence containsa highly conserved TPX2 domain first identified in a microtubule-associated protein (MAP) in Xenopus laevis. Overexpressionof PttMAP20 in Arabidopsis (Arabidopsis thaliana) leads to helical twisting of epidermal cells, frequently associated with MAPs.In addition, a PttMAP20-yellow fluorescent protein fusion protein expressed in tobacco (Nicotiana tabacum) leaves localizes tomicrotubules in leaf epidermal pavement cells. Recombinant PttMAP20 expressed in Escherichia coli also binds specifically to invitro-assembled, taxol-stabilized bovine microtubules. Finally, the herbicide 2,6-dichlorobenzonitrile, which inhibits cellulosesynthesis in plants, was found to bind specifically to PttMAP20. Together with the known function of cortical microtubules inorienting cellulose microfibrils, these observations suggest that PttMAP20 has a role in cellulose biosynthesis.
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