Abstract:In order to explore the correlation between cysteine proteases and the senescence of determinate nodules,LjCyp1 and LjCyp5,associated with root nodule senescence were identified from Lotus japonicus by sequence alignment analysis with cysteine protease AsNODf32.The protein sequence and structure showed that the homology of LjCyp1 and LjCyp5 was as high as 96.2%,both of which contained two typical cysteine protease domains and vacuolar localization signal peptides,belonging to the papain family. In vitro enzyme activity assays showed that both proteins had cysteine protease activity. Realtime PCR and histochemical localization analysis showed that two protease genes were mainly expressed in mature and aged root nodules. The results indicated that LjCyp1 and LjCyp5 cysteine proteases may play an important role during nodule senescence in Lotus japonicus.