Abstract
An unexpected growth-stimulating effect of 5-aminouracil (5-AU) 50, 100 and 150 μM concentration on long-term callus tissue culture of Cereus peruvianus was found during investigations of callus tissue growth and expression of Mdh genes in the presence of this inhibitor of DNA replication. Three-year-old callus tissues were cut and subcultured in culture medium containing the different 5-AU concentrations. The callus tissues were then collected at 15-day intervals up to 45 days to determine individual callus weight. At 45 days, the callus tissues were collected and submitted to starch gel electrophoresis for analysis of MDH isozymes. The in vivo effect of the various 5-AU concentrations on onion root-tip cell growth was also investigated, and a similar growth response pattern was observed. Unchanged MDH isozyme patterns in callus tissues indicated that Mdh gene expression was not directly related to increased growth of the callus tissues. The interference of 5-AU with DNA replication for cell proliferation and tissue did not change the expression of Mdh genes at the transcriptional level but seems to affect important genes that modulate enzyme-specific activity or degradation of MDH isozymes.
