A Change in Tubulin Synthesis in the Process of Tracheary Element Differentiation and Cell Division of Isolated Zinnia Mesophyll Cells

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Changes in tubulin synthesis in the process of cytodifferentiation into tracheary elements and cell division were investigated using a culture of single cells isolated from the mesophyll of Zinnia elegans. The tubulin content was measured by a sensitive immunoblotting method using a mouse monoclonal antibody to α- or β-tubulin as a probe and mung bean tubulin as a standard. Freshly isolated mesophyll cells had only small amounts of tubulin, but the content increased rapidly between 24 and 48 h of culture before morphological differentiation and cell division. The content rose more than sixfold during 48 h culture and then decreased slightly. This pattern of increase closely resembled that of the increase in cortical microtubules (MTs) estimated by electron microscopic analysis. The α- and β-tubulin contents in the cultured cells were almost the same and changed in coordination during culture. The activity of tubulin synthesis was determined by densitometric scanning of spots corresponding to tubulin subunits on an autoradiogram of a two-dimensional polyacrylamide gel of [^<35>S]-methionine-labeled proteins. Tubulin synthesis began as early as between 4 and 8 h of culture and its rate increased similarly to the increase in the tubulin content, with the former always preceding the latter, indicating that the increase in content resulted from new tubulin synthesis.
日本植物生理学会の論文