Auxin starvation results in G2-arrest in suspension-cultured tobacco cells

In cell suspensions of tobacco LT cells, cultured on Linsmaier and Skoog medium with 2,4-dichlorophenoxy-acetic acid (2,4-D) as the sole plant growth regulator, final cell number is dependent on the initial concentration of 2,4-D in the medium. At low concentrations of 2,4-D, accumulation of cells in the G2-phase of the cell cycle appeared to increase. Cells arrested in the G2-phase could enter mitosis and continue cycling after addition of 2,4-D or the auxin analogue NAA. Addition of cytokinins or 3,5-D did not enable passage of the cells into mitosis. This suggests that auxin (analogues) influence a restriction point in the G2-phase of the cell cycle in tobacco LT cells.