ALUMINUM AND LOW PH EFFECTS ON TRANSLATABLE RNA POPULATION FROM BEAN CALLI

We have reproduced in vitro aluminium toxicity on bean calli for the p urpose of analyzing how gene expression is modified by aluminum ions ( Al). We have used three different media. L3m with reduced Ca and P-i c oncentration and a pH of 5.7; L3m4, similar, but with a pH of 4.0; and L3m4Al with the same composition and pH as L3m4, but with Al salt (Al Cl3) (500 mg/l) added. We cultured genotypically identical calli for 2 4 h and 1 month in the three media. Total RNA was obtained from all th e calli and in vitro translated. The polypeptides obtained were resolv ed by two-dimensional poly acrylamide gel electrophoresis (2-D-PAGE) a nd compared. After the 24 h of treatment the three patterns were simil ar and only quantitative differences between L3m4Al-cultured and calli cultured in the two other media were detected. These differences disa ppeared after one month of treatment and new spots were detected in 2- D-PAGE of L3m4- and L3m4Al-cultured calli, but not in L3m. The differe nces observed after the 24-h treatment could be due to the ageing of t he calli rather than to Al toxicity, and those described at 1 month se emed to be mostly related to pH. We suggest that Al does not specifica lly affect gene expression. The induced changes appeared later in time and were mainly related to low pH; only one polypeptide was associate d with Al after the 1-month treatment.