Metabolism of Pyrimidines in Protoplasts from Cultured Catharanthus roseus Cells

The metabolism of [2-¹⁴C]thymine, [2-¹⁴C]thymidine, [2-¹⁴C]uraciland [¹⁴C]uridine was investigated in protoplasts obtained fromsuspension cultures of Catharanthus roseus. Most of the exogenouslysupplied thymine, thymidine and uracil was degraded, and salvageof these pyrimidines accounted for 5–36 per cent of thetotal amount of ¹⁴C-labelled precursors which was metabolized.However, more than 80 per cent of the labelled uridine was utilizedfor the biosynthesis of nucleotides and nucleic acids, and therest was degraded. In contrast to the results from protoplastsof sugar cane cells in suspension culture, the data indicatethat protoplasts possess a pathway for the degradation of pyrimidines,and that the overall metabolism of these pyrimidines in protoplastsis very similar to the metabolism in the intact cells. Catharanthus roseus, madagascar periwinkle, protoplasts, pyrimidine metabolism     

Activities of Enzymes Relating to Starch Synthesis and Endogenous Levels of Growth Regulators in Potato Stolon Tips During Tuberization

Changes in contents of starch and protein, and activities of enzymes involved in starch synthesis were studied during tubcrization of stolon tips of Solanum tuberosum L. cv. Irish Cobbler. Starch content and activities of phosphorylase and granule-bound starch synthctase based on fresh weight increased rapidly in the early phase (stage I, the stolon tips just before swelling; stage 2, the swelling tips; stage 3, young tubers of 0.2–0.5 cm diameter), and they all remained nearly unchanged in the later phase (stage 3 to stage 6, young tubers of 3.5 cm diameter). The content of soluble protein based on fresh weight remained unchanged. Activities of soluble starch snythetase and ADP-glucose pyrophosphorylase were not detected at stage 1 and 2, but increased at later stages. Endogenous levels of auxin, cytokinin and gibberellin were assayed for the materials at the corresponding developmental stages. Auxin content was high at stages 1 and 2, and lowered at later stages. Cytokinin content increased abruptly at stage 6. Gibberellin content was low at all stages. The internal conditions for starch deposition and tuberization in potato were discussed in regard to regulation of enzyme activities by growth regulators.