Publications

• Chlorophyll degradation during senescence.

  Hortensteiner S.

  The catabolic pathway of chlorophyll (Chl) during senescence and fruit ripening leads to the accumulation of colorless breakdown products (NCCs). This review updates an earlier review on Chl breakdown published here in 1999 ( 69 ). It summarizes recent advances in the biochemical reactions of the ... >> More

  The catabolic pathway of chlorophyll (Chl) during senescence and fruit ripening leads to the accumulation of colorless breakdown products (NCCs). This review updates an earlier review on Chl breakdown published here in 1999 ( 69 ). It summarizes recent advances in the biochemical reactions of the pathway and describes the characterization of new NCCs and their formation inside the vacuole. Furthermore, I focus on the recent molecular identification of three chl catabolic enzymes, chlorophyllase, pheophorbide a oxygenase (PAO), and red Chl catabolite reductase (RCCR). The analysis of Chl catabolic mutants demonstrates the importance of Chl breakdown for plant development and survival. Mutants defective in PAO or RCCR develop a lesion mimic phenotype, due to the accumulation of breakdown intermediates. Thus, Chl breakdown is a prerequisite to detoxify the potentially phototoxic pigment within the vacuoles in order to permit the remobilization of nitrogen from Chl-binding proteins to proceed during senescence. << Less

  Annu Rev Plant Biol 57:55-77(2006) [PubMed] [EuropePMC]

  This publication is cited by 6 other entries.

• Chlorophyll Breakdown in Senescent Chloroplasts (Cleavage of Pheophorbide a in Two Enzymic Steps).

  Rodoni S., Muhlecker W., Anderl M., Krautler B., Moser D., Thomas H., Matile P., Hortensteiner S.

  The cleavage of pheophorbide (Pheide) a into primary fluoescent chlorophyll (Chl) catabolites (pFCCs) in senescent chloroplasts was investigated. Chloroplast preparations isolated from senescent canola (Brassica napus) cotyledons exhibited light-dependent production of pFCC when assay mixtures wer ... >> More

  The cleavage of pheophorbide (Pheide) a into primary fluoescent chlorophyll (Chl) catabolites (pFCCs) in senescent chloroplasts was investigated. Chloroplast preparations isolated from senescent canola (Brassica napus) cotyledons exhibited light-dependent production of pFCC when assay mixtures were supplemented with ferredoxin (Fd). pFCC production in detergent-solubilized membranes was dependent on the presence of an Fd-reducing system. Pheide a cleavage required the action of two proteins, Pheide a oxygenase and a stroma protein. In the absence of stroma protein, Pheide a oxygenase converted Pheide a into a red Chl catabolite (RCC), the presumptive intermediary product of Pheide a cleavage. Incubation of the stroma protein (RCC reductase) together with chemically synthesized RCC resulted in the production of three different FCCs. Two of these catabolites were identical to the pFCCs from canola or barley (Hordeum vulgare) (pFCC-1) and sweet pepper (Capsicum annuum) (pFCC-2), respectively. Thus, the conversion of Pheide a to pFCC could be demonstrated to proceed in two consecutive steps, and both reactions depended on reduced Fd as the source of electrons. The function of Fd in Chl breakdown in vivo is corroborated by the marked retention of this protein until the late stages of senescence, as demonstrated by immunoblotting. << Less

  Plant Physiol 115:669-676(1997) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• The key step in chlorophyll breakdown in higher plants. Cleavage of pheophorbide a macrocycle by a monooxygenase.

  Hortensteiner S., Wuthrich K.L., Matile P., Ongania K.H., Krautler B.

  Chlorophyll breakdown in green plants is a long-standing biological enigma. Recent work has shown that pheophorbide a (Pheide a) derived from chlorophyll (Chl) is converted oxygenolytically into a primary fluorescent catabolite (pFCC-1) via a red Chl catabolite (RCC) intermediate. RCC, the product ... >> More

  Chlorophyll breakdown in green plants is a long-standing biological enigma. Recent work has shown that pheophorbide a (Pheide a) derived from chlorophyll (Chl) is converted oxygenolytically into a primary fluorescent catabolite (pFCC-1) via a red Chl catabolite (RCC) intermediate. RCC, the product of the ring cleavage reaction catalyzed by Pheide a oxygenase, which is suggested to be the key enzyme in Chl breakdown in green plants, is converted into pFCC-1 by a reductase. In the present study, an in vitro assay comprising 18O2 Pheide a oxygenase and RCC reductase yielded labeled pFCC-1. Fast atom bombardment-mass spectrometric analysis of the purified pFCC-1 product revealed that only one of the two oxygen atoms newly introduced into Pheide a in the course of the cleavage reaction is derived from molecular oxygen. Analysis of the fragment ions located the oxygen atom derived from molecular oxygen on the formyl group of pyrrole B. This finding demonstrates that the cleavage of Pheide a in vascular plants is catalyzed by a monooxygenase. Chlorophyll breakdown is therefore indicated to be mechanistically related in higher plants and in the green alga Chlorella protothecoides. << Less

  J Biol Chem 273:15335-15339(1998) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• In vivo participation of red chlorophyll catabolite reductase in chlorophyll breakdown.

  Pruzinska A., Anders I., Aubry S., Schenk N., Tapernoux-Luthi E., Muller T., Krautler B., Hortensteiner S.

  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 i ... >> More

  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. << Less

  Plant Cell 19:369-387(2007) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• The role of pheophorbide a oxygenase expression and activity in the canola green seed problem.

  Chung D.W., Pruzinska A., Hortensteiner S., Ort D.R.

  Under normal field growth conditions, canola (Brassica napus) seeds produce chloroplasts during early seed development and then catabolize the photosynthetic machinery during seed maturation, producing mature seeds at harvest that are essentially free of chlorophyll (Chl). However, frost exposure ... >> More

  Under normal field growth conditions, canola (Brassica napus) seeds produce chloroplasts during early seed development and then catabolize the photosynthetic machinery during seed maturation, producing mature seeds at harvest that are essentially free of chlorophyll (Chl). However, frost exposure early in canola seed development disrupts the normal programming of Chl degradation, resulting in green seed at harvest and thereby significantly devaluing the crop. Pheophorbide a oxygenase (PaO), a key control point in the overall regulation of Chl degradation, was affected by freezing. Pheophorbide a, the substrate of PaO, accumulated during late stages of maturation in seeds that had been exposed to freezing during early seed development. Freezing interfered with the induction of PaO activity that normally occurs in the later phases of canola seed development when Chl should be cleared from the seed. Moreover, we found that the induction of PaO activity in canola seed was largely posttranslationally controlled and it was at this level that freezing interfered with PaO activation. The increased accumulation of PaO transcript and protein levels during seed development was not altered by the freezing episode, and the increase in PaO protein was small compared to the increase in PaO activity. We found that PaO could be phosphorylated and that phosphorylation decreased with increasing activity, implicating PaO dephosphorylation as an important posttranslational control mechanism for this enzyme. Two PaO genes, BnPaO1 and BnPaO2, were identified in senescing canola leaves and during early seed development, but only BnPaO2 was expressed in maturing, degreening seeds. << Less

  Plant Physiol 142:88-97(2006) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Chlorophyll breakdown: pheophorbide a oxygenase is a Rieske-type iron-sulfur protein, encoded by the accelerated cell death 1 gene.

  Pruzinska A., Tanner G., Anders I., Roca M., Hortensteiner S.

  Chlorophyll (chl) breakdown during senescence is an integral part of plant development and leads to the accumulation of colorless catabolites. The loss of green pigment is due to an oxygenolytic opening of the porphyrin macrocycle of pheophorbide (pheide) a followed by a reduction to yield a fluor ... >> More

  Chlorophyll (chl) breakdown during senescence is an integral part of plant development and leads to the accumulation of colorless catabolites. The loss of green pigment is due to an oxygenolytic opening of the porphyrin macrocycle of pheophorbide (pheide) a followed by a reduction to yield a fluorescent chl catabolite. This step is comprised of the interaction of two enzymes, pheide a oxygenase (PaO) and red chl catabolite reductase. PaO activity is found only during senescence, hence PaO seems to be a key regulator of chl catabolism. Whereas red chl catabolite reductase has been cloned, the nature of PaO has remained elusive. Here we report on the identification of the PaO gene of Arabidopsis thaliana (AtPaO). AtPaO is a Rieske-type iron-sulfur cluster-containing enzyme that is identical to Arabidopsis accelerated cell death 1 and homologous to lethal leaf spot 1 (LLS1) of maize. Biochemical properties of recombinant AtPaO were identical to PaO isolated from a natural source. Production of fluorescent chl catabolite-1 required ferredoxin as an electron source and both substrates, pheide a and molecular oxygen. By using a maize lls1 mutant, the in vivo function of PaO, i.e., degradation of pheide a during senescence, could be confirmed. Thus, lls1 leaves stayed green during dark incubation and accumulated pheide a that caused a light-dependent lesion mimic phenotype. Whereas proteins were degraded similarly in wild type and lls1, a chl-binding protein was selectively retained in the mutant. PaO expression correlated positively with senescence, but the enzyme appeared to be post-translationally regulated as well. << Less

  Proc. Natl. Acad. Sci. U.S.A. 100:15259-15264(2003) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.