Degradation of chloroplast proteins-
identification and characterization of senescence associated cysteine proteases

Chloroplast proteins are the major source for nitrogen remobilized during leaf senescence. The proteases involved in senescence associated degradation of chloroplast proteins are so far not known. Most of the plastid nitrogen is bound to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in the stroma of chloroplasts. Another considerable fraction of the nitrogen is contained in the apoproteins of the light-harvesting complex II and other pigment protein complexes of the thylakoid membrane. Biochemical analyses suggest that cysteine proteases inside chloroplasts are involved in degradation of chloroplast proteins. Cysteine protease genes showing enhanced expression during senescence are overexpressed in barley. Transgenic plants will be functionally characterized with regard to senescence associated chloroplast protein degradation and nitrogen remobilization.

Insitute of BotanyCAU
University of Kiel, Germany

Prof. Dr. Karin Krupinska
Julien Hollmann
Susann Frank

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