Isotype-specific Changes in the Amount of β-Tubulin RNA in Synchronized Tobacco BY2 Cells

Abstract

The 3’-ends of the β-tubulin cDNA were amplified from tobacco BY2 polyA⁺ RNA. According to the differences in the predicted amino acid sequence at the extreme C-terminal, they were grouped into three different isotypes, NTB1 in which “EEGDYYEEDEEDLNEA”, NTB2 in which “EEEYYEDEEEAQED” and NTB3 in which “DECEYEEEEEYDHEGN” follows the conservative “YQQYQDATAD” sequence. Using unique 3’-untranslated regions as probes, changes in the RNA levels of each β-tubulin isotype were determined by dot-blot hybridization. The levels exhibited characteristic rhythms in the cell cycle. NTB1RNA was highest in S phase in comparison to NTB2 RNA level which was highest in late G2. On the other hand, NTB3 RNA level was highest in early G2.