Cloning and characterization of preferentially expressed genes in an aluminum-tolerant mutant derived from Penicillium chrysogenum IFO4626.

cDNAs expressed preferentially in an Al-tolerant microorganism were isolated by subtraction hybridization with cDNAs of Al-sensitive Penicillium chrysogenum IFO4626 as driver cDNA and cDNAs of the Al-tolerant mutant derived from the wild cells by UV irradiation as tester cDNA. Northern blot analysis revealed that mRNA levels of six genes were increased significantly in the Al-tolerant mutant after exposure to Al stress when compared with the wild cells. Two genes accumulated in both the presence and absence of Al stress and four genes were induced by Al stress in the Al-tolerant mutant. cDNA fragments were amplified by rapid amplification of cDNA ends and sequenced to obtain full-length cDNAs of the six genes. Two genes were novel or predicted ones and the others showed significant homology to known genes, ADP/ATP translocase, enolase, cysteine synthase, and glucoamylase, which are induced by environmental stresses in prokaryotic and eukaryotic cells. These enzyme activities increased in the Al-tolerant mutant when compared to those in the wild cells, showing that not only the levels of gene expression but also the levels of enzyme activities increased in the Al-tolerant mutant.