Perturbation in linker histone content has no effect on the cell cycle butaffects the cell size of suspension grown tobacco BY-2 cells

Histone H1, a key structural element of eukaryotic chromosomes can be pertu rbed in plants in vivo by overexpression or by a change in the proportion o f native H1 variants (Prymakowska-Bosak M., Przewloka M., Iwkiewicz J., Egi erszdorff S., Kuras M., Chaubert N., Gigot C., Spiker S., Jerzmanowski A., Histone H1 overexpressed to high level in tobacco affects certain developme ntal programs but has limited effect on basal cellular functions, Proc. Nat l. Acad. Sci. U.S.A. 93 (1996) 10250-10255; Prymakowska-Bosak AI., Slusarcz yk J., Przewloka M., Kuras M., Lichota J., Kilianczyk B., Jerzmanowski A., Linker Histones Play a Role in Male Meiosis and the Development of Pollen G rains in Tobacco, Plant Cell 11 (1999) 2317-2330). In order to analyze the possible causes of the specific phenotypic changes observed in whole plants we employed a simpler system of tobacco BY-2 cell line. We show that the B Y-2 cells engineered to overexpress a major variant of Arabidopsis H1 or wi th the level of native major variants of H1 decreased by antisense strategy maintain the normal ability to grow and the normal length of the cell cycl e. Tn the cells with perturbed H1 histones no change was observed in the or ganization of mitotic spindle or actin filaments of the cytoskeleton. The o nly visible phenotypic change occurred in cells overexpressing H1 that show ed an increased frequency of cells with unusually large size. This phenotyp e was correlated with subtle but reproducible changes in the organization o f cortical microtubules. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.