Repression of genetic activity in root meristem cells by peptidic factor derived from male sex organs of Chara

Present autoradiographic investigations using H-3-uridine and H-3-leucine i ncorporation indicate that preincubation of primary roots of Melandrium noc tiflorum with antheridial chromatin condensation factor (ACCF), a low molec ular mass peptidic factor (4.5 kDa) obtained from maturing male sex organs of Chara tomentosa, leads to a marked reduction of transcription and transl ation in G1, G2 and endopolyploid cells (8C DNA level). Moreover, silver st aining of cells reveals considerable decrease in number and sizes of nucleo li. The similarities that exist between the "innate" processes within devel oping antheridial filaments of Chara and the genetic repression induced by antheridial peptidic extracts in root cells. of M. noctiflorum seems to pro vide further positive evidence for the presence of a highly specific factor that contributes to nuclear re-patterning of differentiating germ line cel ls in male sex organs of Chara.