Characterization of cathepsin B-like gene from rice

In this study, a rice cDNA clone encoding a putative cysteine protease withsequence homology to mammalian cathepsin B has been isolated and characterized.Sequence analysis revealed that the gene designated OsCatB encodes a cysteine proteasethat belongs to the papain family without the consensus motif, ERFNIN. The resultsuggests that the OsCatB is the cathepsin B-like protein in rice. Among the cathepsin Blikeproteins in plants, the highest homology was occurred to the sequence of the barleycathepsin B. DNA blot analysis showed that the OsCatB gene belongs to a multiple genefamily in the rice genome. Expression analysis of the OsCatB revealed that the gene isexpressed in all organs of rice including the germinating seed. To elucidate OsCatBfunction, we generated knockout mutants by RNAi system. Microscopic analysis revealedthat knockout of the OsCatB gene caused an excessive cell death and suggested that thegene functions as an anti-cell-death component.