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BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Activation of β-Glucan Synthases by Wall-Bound Purple Acid Phosphatase in Tobacco Cells^1,[W],[OA]

Department of Chemical and Biological Sciences, Japan Women's University, Tokyo 112–8681, Japan (R.K., Y.S., Y.Y., T.S.K.); Royal Institute of Technology, School of Biotechnology, AlbaNova University Center, Stockholm SE–10691, Sweden (V.B.); Kyoto University, Research Institute for Sustainable Humanosphere, Gokasho, Uji, Kyoto 611–0011, Japan (R.K., T.K., T.H.); and Institute of Sustainability Science, Kyoto University, Kyoto 611–0011, Japan (T.H.)

Wall-bound purple acid phosphatases have been shown to be potentially involved in the regulation of plant cell growth. The aim of this work was to further investigate the function of one of these phosphatases in tobacco (Nicotiana tabacum), NtPAP12, using transgenic cells overexpressing the enzyme. The transgenic cells exhibited a higher level of phosphatase activity in their walls. The corresponding protoplasts regenerating a cell wall exhibited a higher rate of β-glucan synthesis and cellulose deposition was increased in the walls of the transgenic cells. A higher level of plasma membrane glucan synthase activities was also measured in detergent extracts of membrane fractions from the transgenic line, while no activation of Golgi-bound glycan synthases was detected. Enzymatic hydrolysis and methylation analysis were performed on the products synthesized in vitro by the plasma membrane enzymes from the wild-type and transgenic lines extracted with digitonin and incubated with radioactive UDP-glucose. The data showed that the glucans consisted of callose and cellulose and that the amount of each glucan synthesized by the enzyme preparation from the transgenic cells was significantly higher than in the case of the wild-type cells. The demonstration that callose and cellulose synthases are activated in cells overexpressing the wall-bound phosphatase NtPAP12 suggests a regulation of these carbohydrate synthases by a phosphorylation/dephosphorylation process, as well as a role of wall-bound phosphatases in the regulation of cell wall biosynthesis.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Takahisa Hayashi (taka{at}rish.kyoto-u.ac.jp).

^[W] The online version of this article contains Web-only data.

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www.plantphysiol.org/cgi/doi/10.1104/pp.109.139287

^* Corresponding author; e-mail taka{at}rish.kyoto-u.ac.jp.

Received March 31, 2009; accepted May 14, 2009; published June 3, 2009.