Nitrogen metabolism and remobilization during senescence

Hörtensteiner, Stefan; Feller, Urs (2002). Nitrogen metabolism and remobilization during senescence. Journal of Experimental Botany, 53(370), pp. 927-937. Oxford University Press 10.1093/jexbot/53.370.927

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Senescence is a highly organized and well‐regulated process. As much as 75% of total cellular nitrogen may be located in mesophyll chloroplasts of C3‐plants. Proteolysis of chloroplast proteins begins in an early phase of senescence and the liberated amino acids can be exported to growing parts of the plant (e.g. maturing fruits). Rubisco and other stromal enzymes can be degraded in isolated chloroplasts, implying the involvement of plastidial peptide hydrolases. Whether or not ATP is required and if stromal proteins are modified (e.g. by reactive oxygen species) prior to their degradation are questions still under debate. Several proteins, in particular cysteine proteases, have been demonstrated to be specifically expressed during senescence. Their contribution to the general degradation of chloroplast proteins is unclear. The accumulation in intact cells of peptide fragments and inhibitor studies suggest that multiple degradation pathways may exist for stromal proteins and that vacuolar endopeptidases might also be involved under certain conditions. The breakdown of chlorophyll‐binding proteins associated with the thylakoid membrane is less well investigated. The degradation of these proteins requires the simultaneous catabolism of chlorophylls. The breakdown of chlorophylls has been elucidated during the last decade. Interestingly, nitrogen present in chlorophyll is not exported from senescencing leaves, but remains within the cells in the form of linear tetrapyrrolic catabolites that accumulate in the vacuole. The degradation pathways for chlorophylls and chloroplast proteins are partially interconnected.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS) > Plant nutrition (discontinued)
08 Faculty of Science > Department of Biology > Institute of Plant Sciences (IPS)

UniBE Contributor:

Hörtensteiner, Stefan and Feller, Urs

Subjects:

500 Science > 580 Plants (Botany)

ISSN:

0022-0957

Publisher:

Oxford University Press

Language:

English

Submitter:

Peter Alfred von Ballmoos-Haas

Date Deposited:

17 Dec 2015 16:30

Last Modified:

27 Apr 2018 10:59

Publisher DOI:

10.1093/jexbot/53.370.927

Additional Information:

6th International Symposium on Inorganic Nitrogen Assimilation, REIMS, FRANCE, JUL 08-12, 2001

BORIS DOI:

10.7892/boris.73995

URI:

https://boris.unibe.ch/id/eprint/73995

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