The Pathway of Chlorophyll Degradation: Catabolites, Enzymes and Pathway Regulation

Hörtensteiner, Stefan

doi:10.1007/978-94-007-5724-0_16

Cited by 10 publications

(14 citation statements)

References 198 publications

(288 reference statements)

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“…Next, to confirm that expression of 2YR82aa 101–174 promotes chlorophyll catabolism, we examined the expression levels of two genes encoding pheide A oxygenase (PAO) and pheophytinase (PPH) which are two critical enzymes engaged for chlorophyll degradation (Schelbert et al ., ; Hörtensteiner, ) by quantitative reverse‐transcription PCR (qRT‐PCR). We found that the expression levels of both PAO and PPH were significantly increased in detached leaves of the pER8:2YR82aa 101–174 transgenic lines (#6 and #9) on the 4th day after estrogen treatment (Figure d,e).…”

Section: Resultsmentioning

confidence: 99%

Multiple intramolecular trafficking signals in RESISTANCE TO POWDERY MILDEW 8.2 are engaged in activation of cell death and defense

Huang

Zhang

et al. 2019

The Plant Journal

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The extrahaustorial membrane (EHM) is a host-derived interfacial membrane encasing the haustorium of powdery mildew fungi. Arabidopsis thaliana RESISTANCE TO POWDERY MILDEW 8.2 (RPW8.2) is specifically targeted to the EHM via two EHM-targeting signals. Here, we demonstrate that proper coordination between the trafficking forces engaged via the EHM-targeting signals and the nuclear localization signals (NLSs), as well as the nuclear export signals (NESs), in RPW8.2 is critical for the activation of cell death and defense. We show that in the absence of pathogens, RPW8.2 is partitioned between the cytoplasm and the nucleus, and turned over via both the 26S proteasome-and the vacuole-dependent pathways. Enhanced cytoplasmic localization of RPW8.2 by tagging it with a NES led to lethal cell death. By contrast, enhanced nuclear localization of RPW8.2 by adding an NLS to it resulted in resistance to powdery mildew. Whereas expression of the NES-containing C-terminal domain of RPW8.2 in the cytoplasm is sufficient to trigger cell death, no such cell death-inducing activity is found with RPW8.2 variants that contain the two EHM-targeting signals along with the NES-containing C-terminal domain. In addition, we present evidence for the involvement of a leaf senescence pathway in RPW8.2-mediated cell death and defense. Taken together, our data suggest that RPW8.2 is subject to adjustment by distinct and perhaps coordinated mechanisms for its localization and function via interaction with the multiple intramolecular trafficking signals, which should provide further insights into RPW8.2-activated, EHM-focused resistance against powdery mildew.

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Section: Resultsmentioning

confidence: 99%

Multiple intramolecular trafficking signals in RESISTANCE TO POWDERY MILDEW 8.2 are engaged in activation of cell death and defense

Huang

Zhang

et al. 2019

The Plant Journal

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“…The cleavage of the phytol chain occurs at the early stage of chlorophyll catabolism, including chlorophyll breakdown and turnover (Hörtensteiner, 2013b). Finding the enzymes responsible for the dephytylation reaction is necessary for understanding these issues.…”

Section: Discussionmentioning

confidence: 99%

“…The natural enzyme capable of dephytylating chlorophylls in vivo has been enigmatic (Hörtensteiner, 2013b). Now, at least two enzymes, CLH and CLD1, are capable of cleaving the ester bond of chlorophyll in vitro.…”

Section: Cld1 Is a "Chlorophyllase" Distinct From Clhmentioning

confidence: 99%

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Identification of a Chlorophyll Dephytylase Involved in Chlorophyll Turnover in Arabidopsis

Lin

Charng

2016

Plant Cell

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Chlorophyll turns over in green organs during photosystem repair and is salvaged via de-and rephytylation, but the enzyme involved in dephytylation is unknown. We have identified an Arabidopsis thaliana thylakoid protein with a putative hydrolase domain that can dephytylate chlorophyll in vitro and in vivo. The corresponding locus, CHLOROPHYLL DEPHYTYLASE1 (CLD1), was identified by mapping a semidominant, heat-sensitive, missense allele (cld1-1). CLD1 is conserved in oxygenic photosynthetic organisms, sharing structural similarity with pheophytinase, which functions in chlorophyll breakdown during leaf senescence. Unlike pheophytinase, CLD1 is predominantly expressed in green organs and can dephytylate chlorophyll in vitro. The specific activity is significantly higher for the mutant protein encoded by cld1-1 than the wild-type enzyme, consistent with the semidominant nature of the cld1-1 mutation. Supraoptimal CLD1 activities in cld1-1 mutants and transgenic seedlings led to the proportional accumulation of chlorophyllides derived from chlorophyll dephytylation after heat shock, which resulted in light-dependent cotyledon bleaching. Reducing CLD1 expression diminished thermotolerance and the photochemical efficiency of photosystem II under prolonged moderate heat stress. Taken together, our results suggest that CLD1 is the long-sought enzyme for removing the phytol chain from chlorophyll during its turnover at steady state within the chloroplast.

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“…This has been substantiated by numerous investigations using different approaches, among them GFP fusion protein analysis, subcellular fragmentation studies, and enzyme activity measurements on isolated chloroplast fractions (for recent reviews on the biochemistry of chlorophyll breakdown, see Hörtensteiner, 2013aHörtensteiner, , 2013b. However, the subchloroplast location of respective reactions remained largely unclear until recently, in particular because of the inconsistency with regard to the presence or absence of transmembrane domains in these proteins.…”

Section: Spatial Distribution Of Chlorophyll Catabolic Enzymes Withinmentioning

confidence: 99%

A Role for TIC55 as a Hydroxylase of Phyllobilins, the Products of Chlorophyll Breakdown during Plant Senescence

et al. 2016

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ORCID IDs: 0000-0002-0044-0490 (M.H.); 0000-0002-7598-3609 (S.A.) Chlorophyll degradation is the most obvious hallmark of leaf senescence. Phyllobilins, linear tetrapyrroles that are derived from opening of the chlorin macrocycle by the Rieske-type oxygenase PHEOPHORBIDE a OXYGENASE (PAO), are the end products of chlorophyll degradation. Phyllobilins carry defined modifications at several peripheral positions within the tetrapyrrole backbone. While most of these modifications are species-specific, hydroxylation at the C3 2 position is commonly found in all species analyzed to date. We demonstrate that this hydroxylation occurs in senescent chloroplasts of Arabidopsis thaliana. Using bell pepper (Capsicum annuum) chromoplasts, we establish that phyllobilin hydroxylation is catalyzed by a membrane-bound, molecular oxygen-dependent, and ferredoxin-dependent activity. As these features resemble the requirements of PAO, we considered membrane-bound Rieske-type oxygenases as potential candidates. Analysis of mutants of the two Arabidopsis Rieske-type oxygenases (besides PAO) uncovered that phyllobilin hydroxylation depends on TRANSLOCON AT THE INNER CHLOROPLAST ENVELOPE55 (TIC55). Our work demonstrates a catalytic activity for TIC55, which in the past has been considered as a redox sensor of protein import into plastids. Given the wide evolutionary distribution of both PAO and TIC55, we consider that chlorophyll degradation likely coevolved with land plants.

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The Pathway of Chlorophyll Degradation: Catabolites, Enzymes and Pathway Regulation

Cited by 10 publications

References 198 publications

Multiple intramolecular trafficking signals in RESISTANCE TO POWDERY MILDEW 8.2 are engaged in activation of cell death and defense

Multiple intramolecular trafficking signals in RESISTANCE TO POWDERY MILDEW 8.2 are engaged in activation of cell death and defense

Identification of a Chlorophyll Dephytylase Involved in Chlorophyll Turnover in Arabidopsis

A Role for TIC55 as a Hydroxylase of Phyllobilins, the Products of Chlorophyll Breakdown during Plant Senescence

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