Chlorophyll Breakdown in Senescent Arabidopsis Leaves. Characterization of Chlorophyll Catabolites and of Chlorophyll Catabolic Enzymes Involved in the Degreening Reaction

• Published in: Plant physiology (Bethesda) Vol. 139; no. 1; pp. 52 - 63
• Main Authors: Pružinská, Adriana, Tanner, Gaby, Aubry, Sylvain, Anders, Iwona, Moser, Simone, Můller, Thomas, Ongania, Karl-Hans, Kräutler, Bernhard, Youn, Ji-Young, Liljegren, Sarah J, Hörtensteiner, Stefan
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Biologists 01-09-2005; American Society of Plant Physiologists
• Subjects: Apoptosis Regulatory Proteins - metabolism; Arabidopsis - enzymology; Arabidopsis - metabolism; Arabidopsis Proteins - metabolism; Arabidopsis thaliana; biochemical pathways; Biochemical Processes and Macromolecular Structures; Biological and medical sciences; Canola; Cell Death; Cellular senescence; chlorophyll; Chlorophyll - analogs & derivatives; Chlorophyll - chemistry; Chlorophyll - metabolism; Chlorophylls; DNA, Bacterial - genetics; Enzymes; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; insertional mutagenesis; leaf development; leaf senescence; Leaves; Light; Metabolism; molecular sequence data; Molecular Structure; Mutagenesis, Insertional - genetics; nucleotide sequences; oxidoreductases; Oxidoreductases - metabolism; oxygenases; Oxygenases - genetics; Oxygenases - metabolism; pheide a oxygenase; Phenotype; Phenotypes; phenotypic variation; plant biochemistry; plant genetics; Plant Leaves - enzymology; Plant Leaves - growth & development; Plant Leaves - metabolism; plant morphology; Plant physiology and development; plant proteins; Plants; Polymerase chain reaction; red chlorophyll catabolite reductase; Time Factors; transfer DNA; Chlorophyll; Flower; Senescence; Enzyme; Plant leaf; Gene expression; Arabidopsis thaliana; Oxygenase; Cruciferae; Dicotyledones; Angiospermae; Brassica napus; Development; Spermatophyta; Oxidoreductases; Mutation; Reductase
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.105.065870

During senescence, chlorophyll (chl) is metabolized to colorless nonfluorescent chl catabolites (NCCs). A central reaction of the breakdown pathway is the ring cleavage of pheophorbide (pheide) a to a primary fluorescent chl catabolite. Two enzymes catalyze this reaction, pheide a oxygenase (PAO) and red chl catabolite reductase. Five NCCs and three fluorescent chl catabolites (FCCs) accumulated during dark-induced chl breakdown in Arabidopsis (Arabidopsis thaliana). Three of these NCCs and one FCC (primary fluorescent chl catabolite-1) were identical to known catabolites from canola (Brassica napus). The presence in Arabidopsis of two modified FCCs supports the hypothesis that modifications, as present in NCCs, occur at the level of FCC. Chl degradation in Arabidopsis correlated with the accumulation of FCCs and NCCs, as well as with an increase in PAO activity. This increase was due to an up-regulation of Pao gene expression. In contrast, red chl catabolite reductase is not regulated during leaf development and senescence. A pao1 knockout mutant was identified and analyzed. The mutant showed an age- and light-dependent cell death phenotype on leaves and in flowers caused by the accumulation of photoreactive pheide a. In the dark, pao1 exhibited a stay-green phenotype. The key role of PAO in chl breakdown is discussed.