Post-translational regulation of CND41 protease activity in senescent tobacco leaves.

The degradation of chloroplast proteins is an important occurrence in the mobilization of nutrients from senescing leaves to reproductive organs during senescence. Recently, we proved that tobacco CND41 protease is involved in Rubisco degradation and the translocation of nitrogen during senescence. In this study, we show the post-translational regulation of CND41 protease. Using very specific antibodies that were prepared against CND41-specific peptide (anti-Val 186 to Ser 206), immunoblot analysis clearly indicated a change in the accumulation and processing of CND41 during the maturation of leaves in whole plants. The developmental modification of CND41 was also observed in transgenic tobacco with constitutive expression of CND41 under cauliflower mosaic virus 35S promoter. Further studies of seedlings under senescence induced by combined treatment with nitrogen-starvation and high sucrose confirmed that the processing of CND41 was important for protease activity and senescence. A possible mechanism for the regulation of CND41 activity is discussed.