Elevated Levels of Tubulin Transcripts Accompany the GA_3-Induced Elongation of Oat Internode Segments

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Plant cell elongation involves the deposition of nascent cellulose microfibrils, the orientation of which is regulated in part by the cortical microtubule array. To determine whether changes in tubulin gene expression are associated with cell elongation, we examined GA_3-elicited growth of excised internode segments of A vena sativa. Internode elongation was barely detectable after 6 h of GA_3 treatment, when levels of beta-tubulin transcripts had increased 5-6 fold over levels found in untreated controls. Elongation continued for 48 h, whereas tubulin transcript levels reached a peak at 24 h and then declined. The extent of internode elongation and the level of tubulin transcript accumulation were dependent upon both concentration and duration of GA_3 treatment. Although a I h pulse of GA_3 treatment was sufficient to induce elongation and enhance tubulin transcript levels, constant GA_3 application was necessary to elicit the maximum growth and transcript accumulation responses. Inhibition of internode elongation by abscisic acid and 2,6,dichlorobenzonitrile (an inhibitor of cellulose biosynthesis) or cycloheximide inhibited the GA_3-mediated growth response and the accompanying elevation of tubulin transcript levels. The strong correlation we observed between internode elongation and tubulin transcript level suggests that tubulin gene expression is regulated in close association with cell elongation.
日本植物生理学会の論文