MAP20, a Microtubule-Associated Protein in the Secondary Cell Walls of Hybrid Aspen, Is a Target of the Cellulose Synthesis Inhibitor 2,6-Dichlorobenzonitrile

• Published in: Plant physiology (Bethesda) 2008-11, Vol.148 (3), p.1283-1294
• Main Authors: Rajangam, Alex S, Kumar, Manoj, Aspeborg, Henrik, Guerriero, Gea, Arvestad, Lars, Pansri, Podjamas, Brown, Christian J.-L, Hober, Sophia, Blomqvist, Kristina, Divne, Christina, Ezcurra, Ines, Mellerowicz, Ewa, Sundberg, Björn, Bulone, Vincent, Teeri, Tuula T
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; angiosperm trees; Antibodies; arabidopsis-thaliana; Base Sequence; Biochemical Processes and Macromolecular Structures; Biological and medical sciences; Biosynthesis; carbohydrate-active enzymes; Cell Wall - drug effects; Cell Wall - metabolism; Cell walls; Cellulose - antagonists & inhibitors; Cellulose - blood; conifer tracheids; cortical microtubules; DNA Primers; Epidermal cells; Fundamental and applied biological sciences. Psychology; Gene Expression Profiling; Hybridization, Genetic; kinesin-like; Microtubule-Associated Proteins - chemistry; Microtubule-Associated Proteins - drug effects; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - metabolism; Microtubules; Molecular Sequence Data; Nitriles - pharmacology; Plant cells; plant functional genomics; Plant physiology and development; Plant tissues; Plants; plasma-membrane; protein; Proteins; Sequence Homology, Amino Acid; Tissue samples; Trees - metabolism; urea solution; wood formation
• ISSN: 0032-0889; 1532-2548; 1532-2548
• DOI: 10.1104/pp.108.121913

We have identified a gene, denoted PttMAP20, which is strongly up-regulated during secondary cell wall synthesis and tightly coregulated with the secondary wall-associated CESA genes in hybrid aspen (Populus tremula x tremuloides). Immunolocalization studies with affinity-purified antibodies specific for PttMAP20 revealed that the protein is found in all cell types in developing xylem and that it is most abundant in cells forming secondary cell walls. This PttMAP20 protein sequence contains a highly conserved TPX2 domain first identified in a microtubule-associated protein (MAP) in Xenopus laevis. Overexpression of 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 to microtubules in leaf epidermal pavement cells. Recombinant PttMAP20 expressed in Escherichia coli also binds specifically to in vitro-assembled, taxol-stabilized bovine microtubules. Finally, the herbicide 2,6-dichlorobenzonitrile, which inhibits cellulose synthesis in plants, was found to bind specifically to PttMAP20. Together with the known function of cortical microtubules in orienting cellulose microfibrils, these observations suggest that PttMAP20 has a role in cellulose biosynthesis.