Abstract
In order to develop the methods for bioremediation of acidic soil using leguminous plants, we isolated a total of 23 proton tolerant (PTO) genes by functional screening of a soybean cDNA library with Escherichia coli expression system. We identified their orthologous genes in Arabidopsis thaliana by the blastp program. The orthologs of PTO49 includes three paralogs designated AtPTO49a, AtPTO49b, and AtPTO49c. The identity of the predicted amino acid sequences between AtPTO49a and AtPTO49b is 83 %, and the two paralogs are clustered into the same branch as PTO49 in the phylogenetic tree. The three paralogs showed the same organ specificity of expression. However, a knockout mutant of atpto49b showed obvious hypersensitivity to acid stress and morphological abnormality of leaf whereas atpto49a exhibited only mild acid sensitivity. These results suggests that each paralogous PTO49-like gene has distinct function.
