CYTOKININ AND AUXIN-INDUCED REGULATION OF PROTEIN-SYNTHESIS AND POLY (A)-ROSEUS CELL-CULTURES( RNA ACCUMULATION IN CATHARANTHUS)

2,4-dichlorophenoxyacetic acid (2,4-D)-dependent C. roseus cells were grown for three days in a 2,4-D-free medium, then treated with 4.5 mu M 2,4-D, 5 mu M zeatin or 4.5 mu M 2,4-D + 5 mu M zeatin. Hormone-trea ted cells were labelled in vivo with [S-35]-methionine and polypeptide s were analyzed by two-dimensional polyacrylamide gel electrophoresis. Translation products of poly (A)(+) RNAs isolated from cells treated with hormones were also taken as indicators of differential gene expre ssion. Hormone treatments did not achieve dramatic changes in polypept ide patterns and changes in in vitro polypeptide synthesis were fewer than those encountered in vivo. However, accumulation of specific RNAs coding for 18 and 28 kDa polypeptides was demonstrated under conditio ns of alkaloid production in the cells (i.e., when cells were grown in 2,4-D-free, zeatin-containing medium). Their molecular masses and iso electric points are identical to those of two polypeptides whose in vi vo synthesis are similarly regulated by 2,4-D and for zeatin. These po lypeptides are candidates for a direct or indirect regulatory role in alkaloid synthesis in C. roseus cells, and particularly the polypeptid e of 28 kDa whose in vivo and in vitro synthesis are repressed by 2,4D , yet enhanced by zeatin. Another polypeptide of 16 kDa might be deriv ed from the 18 kDa polypeptide in a post-translational process.