Aluminum and low pH effects on translatable RNA population from bean calli

Summary We have reproduced in vitro aluminium toxicity on bean calli for the purpose of analyzing how gene expression is modified by aluminum ions (Al). We have used three different media. L3m with reduced Ca and P i concentration 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 (AlCl 3 ) (500 mg/l) added. We cultured genotypically identical calli for 24 h and 1 month in the three media. Total RNA was obtained from all the calli and in vitro translated. The polypeptides obtained were resolved by two-dimensional polyacrylamide gel electrophoresis (2-D-PAGE) and compared. After the 24 h of treatment the three patterns were similar and only quantitative differences between L3m4Al-cultured and calli cultured in the two other media were detected. These differences disappeared 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 differences observed after the 24-h treatment could be due to the ageing of the calli rather than to Al toxicity, and those described at 1 month seemed to be mostly related to pH. We suggest that Al does not specifically affect gene expression. The induced changes appeared later in time and were mainly related to low pH; only one polypeptide was associated with Al after the 1-month treatment.