Screening of rice genes from the cDNA catalog using the data obtained by protein sequencing

The partial amino acid sequences of 121 rice proteins separated by two-dimensional gel electrophoresis (2D-PAGE), were determined for a protein sequence data file. In the Rice Genome Research Program (RGP), more than 20,000 cDNA clones randomly selected from rice cDNA libraries have been sequenced to construct a cDNA catalog. Complimentary DNAs encoding about 30% of proteins in the protein sequence data file could be identified in the catalog by computer search. It was deduced that 20,000-40,000 genes are present in the rice genome. Only half of about 20,000 cDNAs sequenced in the RGP, corresponding to 1/4-1/2 of genes present in the entire rice genome, should have unique sequences after considering gene redundancy. This is consistent with the fact that the cDNAs encoding about 30% of the sequenced proteins could be identified in the catalog. If the size of the cDNA catalog is enlarged further, cDNAs encoding all proteins separated by 2D-PAGE could be easily identified from the catalog by using the protein sequence data.