Evidence for the occurrence of multiple aspartic proteinases in rice seeds

Using reverse transcription polymerase chain reaction (RT-PCR), we identified two cDNA fragments encoding aspartic proteinases (APs). The encoded proteins, pL4 and pL5, are similar in sequence to other plant APs including barley AP and cardoon flower AP (cyprosin). The identity was 58-76% with one another. Genomic Southern blot analysis suggested that the rice AP gene constitutes a multigene family.