title: In vivo participation of red chlorophyll catabolite reductase in chlorophyll breakdown.
abstract: A central reaction of chlorophyll breakdown, porphyrin ring opening of pheophorbide a to the primary fluorescent chlorophyll catabolite (pFCC), requires pheophorbide a oxygenase (PAO) and red chlorophyll catabolite reductase (RCCR), with red chlorophyll catabolite (RCC) as a presumably PAO-bound intermediate. In subsequent steps, pFCC is converted to different fluorescent chlorophyll catabolites (FCCs) and nonfluorescent chlorophyll catabolites (NCCs). Here, we show that RCCR-deficient Arabidopsis thaliana accumulates RCC and three RCC-like pigments during senescence, as well as FCCs and NCCs. We also show that the stereospecificity of Arabidopsis RCCR is defined by a small protein domain and can be reversed by a single Phe-to-Val exchange. Exploiting this feature, we prove the in vivo participation of RCCR in chlorophyll breakdown. After complementation of RCCR mutants with RCCRs exhibiting alternative specificities, patterns of chlorophyll catabolites followed the specificity of complementing RCCRs. Light-dependent leaf cell death observed in different RCCR-deficient lines strictly correlated with the accumulation of RCCs and the release of singlet oxygen, and PAO induction preceded lesion formation. These findings suggest that RCCR absence causes leaf cell death as a result of the accumulation of photodynamic RCC. We conclude that RCCR (together with PAO) is required for the detoxification of chlorophyll catabolites and discuss the biochemical role(s) for this enzyme.
authors.affiliation: Institute of Plant Sciences, University of Bern, CH-3013 Bern, Switzerland.
authors.forename: Adriana
authors.initials: A
authors.lastname: Pruzinská
authors.forename: Iwona
authors.initials: I
authors.lastname: Anders
authors.forename: Sylvain
authors.initials: S
authors.lastname: Aubry
authors.forename: Nicole
authors.initials: N
authors.lastname: Schenk
authors.forename: Esther
authors.initials: E
authors.lastname: Tapernoux-Lüthi
authors.forename: Thomas
authors.initials: T
authors.lastname: Müller
authors.forename: Bernhard
authors.initials: B
authors.lastname: Kräutler
authors.forename: Stefan
authors.initials: S
authors.lastname: Hörtensteiner
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry / Q000502:physiology*; D017360:Arabidopsis / Q000201:enzymology* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000502:physiology*; D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism*; D005453:Fluorescence; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010088:Oxidoreductases / Q000737:chemistry / Q000502:physiology*; D010105:Oxygenases / Q000378:metabolism; D010641:Phenotype; D010860:Pigments, Biological / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D051017:Apoptosis Regulatory Proteins; D029681:Arabidopsis Proteins; D010860:Pigments, Biological; D002734:Chlorophyll; D010088:Oxidoreductases; D010105:Oxygenases; C112915:pheide a oxygenase; C408689:ACD2 protein, Arabidopsis