The role of histones in the restriction of chromatin activity in successive stages of development of the antheridial filaments of Chara vulgaris L.
The binding of 3H actinomycin D(3H AMD) was studied autoradiographically and the extinction following Feulgen's reaction at short (5 minutes) hydrolysis in 1N HCl was investigated cytophotometrically in 4 successive (4-, 8-, 16-, and 32-cell) generations of synchronously dividing antheridial filaments of Chara vulgaris L. Four stages of interphase, i.e. early and late S and early and late G2 were taken into consideration in each generation. The intensity of 3H AMD binding, except for early S, declines gradually in successive generations, i.e. in the developmental stages of antheridial filaments. Each generation reveals the highest radioactivity in the cells of early G2. Removal of lysine-rich histones in late G2 is the more effective for enhancing 3H AMD binding the more advanced is the stage of development of antheridial filaments. In early phase S extraction of arginine- or lysine-rich histones stimulates the binding of 3H AMD in the same degree. When all histones are removed, differences in the intensity of 3H AMD binding between particular generations of antheridial filaments disappear altogether. After a 5 minutes hydrolysis Feulgen's reaction reveales mainly loose chromatin, whereas after 16 minutes compact chromatin predominates. Removal of lysin-rich histones brings about an increased extinction after a 5 minutes hydrolysis in all phases of the cell cycle and in all developmental stages of antheridial filaments. After 5 minutes of hydrolysis, the extinction value per nuclear area in all experimental series, despite identical DNA content, undergoes a gradual reduction with the diminishing nuclear volume in the successive generations of antheridial filaments. This reduction is correlated with a decreased intensity of 3H AMD binding. The obtained data indicate that a decline in chromatin cativity in successive developmental stages of antheridial filaments of Chara vulgaris L. is caused by the progressing condensation of chromatin for which lysin-rich histones are responsible.
D001345:Autoradiography; D002843:Chromatin / Q000378:metabolism*; D006657:Histones / Q000502:physiology*; D008938:Mitosis; D010783:Photometry; D063245:Plant Development; D010944:Plants / Q000378:metabolism
D002843:Chromatin; D006657:Histones