THE RELATIONSHIP BETWEEN THE ACCUMULATION OF A 28 KD POLYPEPTIDE AND THAT OF INDOLE ALKALOIDS IN CATHARANTHUS-ROSEUS CELL-SUSPENSION CULTURES

We previously found that the accumulation of the indole alkaloid ajmal icine and that of a polypeptide of 28 kD were induced by 2,4-dichlorop henoxyacetic acid removal in periwinkle (Catharanthus roseus) cell cul tures and further increased by zeatin addition to the culture medium. In this work, we compared the effect of various plant growth regulator s and stresses on the accumulation patterns of both compounds. In a fi rst series of experiments, the periwinkle cells were subcultured in au xin-free medium for five passages and their contents in ajmalicine and 28 kD polypeptide analysed. The maximal biomass progressively decreas ed along subcultures; the 28 kD polypeptide and ajmalicine accumulated concomitantly in the cells (treated with or without zeatin) up to the third passage bur: fully disappeared afterwards. In a second series o f experiments, treatment with gibberellic acid deeply inhibited, where as NaCl treatment (given together with or without zeatin) increased th e accumulation of both ajmalicine and the 28 kD polypeptide. Moreover, growing the cells in hypoxia for 2 days inhibited the accumulation of both compounds. These concomitant changes in the accumulation pattern of ajmalicine and the 28 kD polypeptide suggest: that the latter can play a (direct or indirect) regulatory role in the indole alkaloid pat hway of periwinkle cells.