Changes in the Synthesis of RNA and Protein during Tracheary Element Differentiation in Single Cells Isolated from the Mesophyll ofZinnia elegans

摘要

Cycloheximide (CH) prevented tracheary element (TE) differentiation and cell division in a culture of single cells isolated from the mesophyll ofZinnia elegansat the concentrations which inhibited incorporation of 14C-leucine into protein. When the cells were pulse-treated with this inhibitor for 12 h at various times of culture, TE formation was inhibited most strongly by the treatments made between 24 and 60 h of culture. Incorporation of 14C-leucine into protein showed a high level during this period. The inhibitory effect of actinomycin D (Act-D) on TE differentiation was also marked when it was administered from 24 to 60 h of culture when incorporation of 14C-uridine into nucleic acid was at a high level. These results indicate that RNA and protein syntheses are prerequisites for cytodifferentiation to TE and that the syntheses between 24 and 60 h of culture are closely associated with cytodifferentiation.Studies of qualitative changes in proteins using two-dimensional electrophoresis revealed that approximately 400 polypeptides extracted from 35S-methionine-labeled cells could be reproducibly resolved and that most of them were synthesized in both differentiating and non-differentiating cells. During TE differentiation, however, the synthesis of two polypeptides was shut off and two other polypeptides were newly synthesized between 48 and 60 h of culture, preceding the morphological changes. The relationship between TE differentiation and the synthesis of RNA and protein is discussed.