Aspects of DNA, RNA and protein synthesis during somatic embryogenesis in a carrot cell suspension culture

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Abstract
Changes in DNA, RNA and protein content, incorporation of 3H‐thymidine, 14C‐uridine and 3H‐leucine and template activity of chromatin were investigated in the early process of somatic embryogenesis in a carrot (Daucus carota L. cv. Kurodagosun) cell suspension culture using a synchronous system. An embryogenetic culture in a medium containing 10‐7M zeatin was compared with a non‐embryogenetic culture in a medium containing 10‐7M zeatin and 5 x 10‐7M 2,4‐D. DNA was synthesized very actively prior to and during the formation of globular embryos in the embryogenetic culture. The RNA and protein content per tube increased at an almost constant rate in both cultures, while the rate of incorporation of labelled precursors of RNA and protein rose much more prior to active DNA synthesis in the embryogenetic culture than in the non‐embryogenetic culture. Template activity of chromatin was high in the early stage of embryogenesis in the embryogenetic culture. The results obtained here showed that synthesis and turnover of RNA and protein became active prior to active DNA synthesis in the early stage of embryogenesis, and that these changes at macromolecular levels may play important roles in embryogenesis.