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Enzyme Nomenclature
Information on EC 1.1.1.294 - chlorophyll(ide) b reductase
for references in articles please use BRENDA:EC1.1.1.294
Word Map on EC 1.1.1.294
- 1.1.1.294
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stay-green
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light-harvesting
- oxygenase
- chloroplast
- pheophorbide
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thylakoids
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photosystem
- barley
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dark-induced
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hordeum
- lhcii
- vulgare
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reductases
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7-hydroxymethyl
- cotyledon
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acclimation
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ripening
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chlorophyll-binding
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grana
- pao
- etioplasts
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land
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postharvest
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photochemistry
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degreening
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storability
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storable
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peel
- chlorophyllase
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senescence-induced
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pheophytinase
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The enzyme appears in viruses and cellular organisms
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EC NUMBER 
COMMENTARY 
1.1.1.294
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RECOMMENDED NAME
GeneOntology No.
chlorophyll(ide) b reductase
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
71-hydroxychlorophyllide a + NAD(P)+ = chlorophyllide b + NAD(P)H + H+
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PATHWAY
BRENDA Link
KEGG Link
MetaCyc Link
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SYSTEMATIC NAME
IUBMB Comments
71-hydroxychlorophyllide-a:NAD(P)+ oxidoreductase
This enzyme carries out the first step in the conversion of chlorophyll b to chlorophyll a. It is involved in chlorophyll degradation, which occurs during leaf senescence [3] and it also forms part of the chlorophyll cycle, which interconverts chlorophyll a and b in response to changing light conditions [4,5].
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CAS REGISTRY NUMBER
COMMENTARY
185915-08-6
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
isozymes NYC1 and NOL, i.e Non-Yellow Coloring1 and Non-Yellow Coloring1-Like , encoded by genes nyc1 and nol, respectively
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two isoforms of chlorophyll b reductase termed NYC1 and NOL, respectively
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two isoforms of chlorophyll b reductase termed NYC1 and NOL, respectively
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
evolution
malfunction
metabolism
physiological function
additional information
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rice mutants lacking either NYC1 or NOL are deficient in chlorophyll b reductase activity during leaf senescence. Recombinant NOL enzyme shows in vitro chlorophyll b reductase activity in the absence of NYC1, it is possible that NOL could function independently of NYC1. It is possible that the heterodimer formation of NYC1 and NOL is necessary only under specific developmental conditions such as leaf senescence
evolution
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chlorophyll b reductase belongs to the short-chain dehydrogenase superfamily
evolution
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chlorophyll b reductase belongs to the short-chain dehydrogenase superfamily
evolution
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chlorophyll b reductase belongs to the short-chain dehydrogenase superfamily
malfunction
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Arabidosis thaliana mutants lacking either NYC1 or NOL are deficient in chlorophyll b reductase activity during leaf senescence. Impairment in the chlorophyll b reduction leads to LHC stabilization during leaf senescence in the rice mutant lacking chlorophyll b reductase
malfunction
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rice mutants lacking either NYC1 or NOL are deficient in chlorophyll b reductase activity during leaf senescence. Impairment in the chlorophyll b reduction leads to LHC stabilization during leaf senescence in the rice mutant lacking chlorophyll b reductase
malfunction
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germination rates of mutants rapidly decrease during storage, the non-yellow coloring1 (nyc1)/nyc1-like (nol) mutant seeds fail to germinate after storage for 23 months, whereas 75% of the wild-type seeds germinate after 42 months. Mutations in the chlorophyll degradation enzymes, e.g. in chlorophyll b reductase, result in the stay-green phenotype in leaves, only a nyc1 mutation was accompanied by a stay-green phenotype in Arabidopsis thaliana. Lack of chlorophyll b reductase results in the retention of LHC proteins as well as both chlorophyll a and b that are associated with LHC proteins in leaves. Large amount of LHCII apoproteins accumulated in the nyc1 and nyc1/nol mutants
metabolism
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three enzymes participating in the chlorophyll cycle, namely, chlorophyllide a oxygenase, chlorophyll b reductase, and 7-hydroxymethylchlorophyll reductase, overview. In the reverse reactions from chlorophyll b to chlorophyll a, the 7-formyl group of chlorophyll b is first reduced to a hydroxyl group by the action of chlorophyll b reductase. The activities of chlorophyll b reductase and7-hydroxymethylchlorophyll reductase are coordinated in their regulation, otherwise, imbalance of those activities may lead to accumulation of the intermediate of the pathway. The conversion of chlorophyll b into chlorophyll a precedes the degradation of LHC during leaf senescence
metabolism
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three enzymes participating in the chlorophyll cycle, namely, chlorophyllide a oxygenase, chlorophyll b reductase, and 7-hydroxymethylchlorophyll reductase, overview. In the reverse reactions from chlorophyll b to chlorophyll a, the 7-formyl group of chlorophyll b is first reduced to a hydroxyl group by the action of chlorophyll b reductase. The activities of chlorophyll b reductase and7-hydroxymethylchlorophyll reductase are coordinated in their regulation, otherwise, imbalance of those activities may lead to accumulation of the intermediate of the pathway. The conversion of chlorophyll b into chlorophyll a precedes the degradation of LHC during leaf senescence
metabolism
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three enzymes participating in the chlorophyll cycle, namely, chlorophyllide a oxygenase, chlorophyll b reductase, and 7-hydroxymethylchlorophyll reductase, overview. In the reverse reactions from chlorophyll b to chlorophyll a, the 7-formyl group of chlorophyll b is first reduced to a hydroxyl group by the action of chlorophyll b reductase. The activities of chlorophyll b reductase and7-hydroxymethylchlorophyll reductase are coordinated in their regulation, otherwise, imbalance of those activities may lead to accumulation of the intermediate of the pathway. The conversion of chlorophyll b into chlorophyll a precedes the degradation of LHC during leaf senescence
metabolism
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the enzyme is part of the chlorophyll metabolism pathway, overview. Chlorophyll b reductase catalyzes the conversion of chlorophyll b to 7-hydroxymethyl chlorophyll a, which is the first step in chlorophyll b degradation
physiological function
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when greening seedlings are transferred back to darkness, conversion of chlorophyll b to chlorophyll a occurs, which results in degradation of LHC and an increase in the core antenna complexes
physiological function
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chlorophyll b reductase plays an essential role in maturation and storability of seeds. Both isozymes NYC1 and NOL participate in chlorophyll degradation during seed maturation
physiological function
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inflorescence degreening is associated with increased mRNA abundance of NYC1, pheophytin pheophorbide hydrolase and pheophorbide a oxygenase. Mutants of NYC1 show preferential retention of chlorophyll b during dark incubation
physiological function
isoform NYC1 degrades the chlorophyll b on photosystem II under high-light conditions, thus decreasing the photosystem II content. During high-light treatment, the chlorophyll a/b ratio is stable in the wild-type and plants lacking NYC1-Like (NOL) activity, and the photosystem II content decreases in wiild-type plants. The chlorophyll a/b ratio decreases in the NYC1 and NYC1/NOL deficient plants, and a substantial degree of photosystem II is retained in NYC1/NOL deficient plants after the high-light treatment; NOL is not the primary enzyme responsible for degradation. During high-light treatment, the chlorophyll a/b ratio is stable in the wild-type and plants lacking NYC1-Like (NOL) activity, and the photosystem II content decreases in wiild-type plants. The chlorophyll a/b ratio decreases in NYC1/NOL deficient plants, and a substantial degree of photosystem II is retained in NYC1/NOL deficient plants after the high-light treatment
physiological function
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when the level of chlorophyll b is enhanced by the introduction of a truncated chlorophyllide a oxygenase gene and leaves are incubated in the dark, the amount of NYC1 is greatly increased compared while the amount of NYC1 mRNA is the same as in the wild type. In contrast, NYC1 does not accumulate in the mutant without chlorophyll b. The NYC1 level is related to the energetically uncoupled light-harvesting chlorophyll a/b protein complex
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
zinc (132R)-pheophorbide b + NADPH + H+
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zinc (132S)-pheophorbide b is a better substrate than zinc (132R)-pheophorbide b
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zinc (132S)-pheophorbide b + NADPH + H+
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zinc (132S)-pheophorbide b is a better substrate than zinc (132R)-pheophorbide b
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?
additional information
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chlorophyll b reduction is considered to be an early and obligatory step of chlorophyll b breakdown
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71-hydroxychlorophyllide a + NADP+
chlorophyllide b + NADPH + H+
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?
71-hydroxychlorophyllide a + NADP+
chlorophyllide b + NADPH + H+
chlorophyll b is important for LHCP stability, and no pigment-bound LHCP is detected in chlorophyll b-deficient mutants
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71-hydroxychlorophyllide a + NADP+
chlorophyllide b + NADPH + H+
the enzyme NYC1 is required for proper chloroplast degeneration, chlorophyll b is important for LHCP stability, and no pigment-bound LHCP is detected in chlorophyll b-deficient mutants
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chlorophyll b + NADPH
7-hydroxymethyl chlorophyll a + NADP+
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when purified trimeric photosystem II is incubated with recombinant chlorophyll b reductase (NOL), conversion of chlorophyll b in photosystem II to 7-hydroxymethyl chlorophyll a. Chlorophyll b reductase catalyzes the initial step of photosystem II degradation
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chlorophyll b + NADPH
7-hydroxymethyl chlorophyll a + NADP+
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catalyzed by recombinant NOL, whereas NYC1 protein alone shows no activity, but it is required for a functional chlorophyll b reductase
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?
chlorophyllide b + NADPH + H+
7-hydroxychlorophyllide a + NADP+
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?
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
additional information
?
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chlorophyll b reduction is considered to be an early and obligatory step of chlorophyll b breakdown
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71-hydroxychlorophyllide a + NADP+
chlorophyllide b + NADPH + H+
Q5N800, Q84ST4
chlorophyll b is important for LHCP stability, and no pigment-bound LHCP is detected in chlorophyll b-deficient mutants
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?
71-hydroxychlorophyllide a + NADP+
chlorophyllide b + NADPH + H+
Q5N800, Q84ST4
the enzyme NYC1 is required for proper chloroplast degeneration, chlorophyll b is important for LHCP stability, and no pigment-bound LHCP is detected in chlorophyll b-deficient mutants
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?
chlorophyllide b + NADPH + H+
7-hydroxychlorophyllide a + NADP+
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?
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COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
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INHIBITORS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
additional information
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chlorophyll b reductase decreases during senescence and finally disappears after 8-day-dark incubation
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ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
additional information
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NYC1 and NO have enhanced expression in senescing tissues
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SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SOURCE
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expression of NYC1 during embryo development and regulation, semiquantitative reverse transcription-PCR analysis, overview
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innercellular structures of the enzyme wild-type and mutant seeds
additional information
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isozymes NOL and NYC1 are differentially expressed in Arabidopsis during development
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during fruit development, no obvious change of chlorophyll b reductase mRNA is found. Chlorophyll loss is greatly accelerated by postharvest ethylene fumigation, and NYC transcript abundance is only related to accelerated chlorophyll degradation in ethylene-induced degreening
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during fruit development, no obvious change of chlorophyll b reductase mRNA is found. Chlorophyll loss is greatly accelerated by postharvest ethylene fumigation, and NYC transcript abundance is only related to accelerated chlorophyll degradation in ethylene-induced degreening
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low abundance of mRNA and protein in green leaves, levels increase in response to dark-induced senescence
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a pronounced maximum of Chl b reductase activity at day 2 of senescence
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LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
NYC1 is a transmembrane protein with three transmembrane domains
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NYC1 isoform has three putative membrane-spanning domains, while NOL does not contain any predictable membrane-spanning domains
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NYC1 isoform has three putative membrane-spanning domains, while NOL does not contain any predictable membrane-spanning domains
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NYC1 isoform has three putative membrane-spanning domains, while NOL does not contain any predictable membrane-spanning domains
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the bulk of activity (83%) is found in the thylakoids and only traces (5%) in the envelope fraction
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NOL is localized on the stromal side of the thylakoid membrane despite the lack of a transmembrane domain. NOL and NYC1 interact physically in vitro, NOL and NYC1 are co-localized in the thylakoid membrane and act in the form of a complex as a chlorophyll b reductase
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NYC1 protein may have three transmembrane spanning domains. NOL is located on the stromal surface of the thylakoid membrane. NYC1 and NOL interact with one another, forming a functional chlorophyll b reductase complex
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STORAGE STABILITY
ORGANISM
UNIPROT
LITERATURE
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
by centrifugation, sonication, on a nickel column and by ultrafiltration
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
coding region of chlorophyll b reductase (NOL) lacking its transit peptide amplified and cloned into pET-30a(+) at NspV and HindIII sites, expressed in Escherichia coli Rosetta DE3
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fusion of the region encoding the putative transit peptide of NOL to the green fluorescent protein (GFP) gene and introduced into the epidermal cells of Allium cepa by particle bombardment
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gene nol, DNA and amino acid determination and anaylsis, phylogenetic tree, promoter analysis, semiquantitative RT-PCR expression analysis, overview; gene nyc1, DNA and amino acid determination and anaylsis, phylogenetic tree, promoter analysis, semiquantitative RT-PCR expression analysis, overview
genes nyc1 and nol, the NYC1 promoter contains a potential abscisic acid-responsive element, semiquantitative reverse transcription-PCR expression analysis of isozymes
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EXPRESSION
ORGANISM
UNIPROT
LITERATURE
Chlorophyll loss in fruit peel is greatly accelerated by postharvest ethylene fumigation, which greatly increases the expression of chlorophyll b reductase NYC and chlorophyllase Chlase. The increase in Chlase and NYC transcript abundance is only related to accelerated chlorophyll degradation in ethylene-induced degreening
NYC1 expression is repressed in the abscisic acid-insensitive mutants during embryogenesis
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Chlorophyll loss in fruit peel is greatly accelerated by postharvest ethylene fumigation, which greatly increases the expression of chlorophyll b reductase NYC and chlorophyllase Chlase. The increase in Chlase and NYC transcript abundance is only related to accelerated chlorophyll degradation in ethylene-induced degreening
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Chlorophyll loss in fruit peel is greatly accelerated by postharvest ethylene fumigation, which greatly increases the expression of chlorophyll b reductase NYC and chlorophyllase Chlase. The increase in Chlase and NYC transcript abundance is only related to accelerated chlorophyll degradation in ethylene-induced degreening
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
P360S
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mutation changes the 3D structure of the NADPH binding site, leading to delays in postharvest degreening
additional information
additional information
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Arabidopsis nol/nyc1 double mutant, when the genes for chlorophyll b reductases NOL and NYC1 are disrupted, chlorophyll b and photosystem II are not degraded during senescence, whereas other pigment complexes completely disappear
additional information
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a double mutant constructed between nyc1 and cao (enzyme for chlorophyll b biosynthesis) fails to display a stay-green phenotype during dark-induced senescence
additional information
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a mutation producing a termination codon, and a mutation interfering with correct intron splicing both lead to delays in postharvest degreening
additional information
the non-yellow coloring, nyc1, recessive mutant is a rice stay-green phenotype mutant due to a defect in chlorophyl degradation, in which chlorophyll degradation during senescence is impaired, the mutant NYC1 does not show chlorophyll b reductase activity, but NOL, i.e. NYC1-like, a protein closely related to NYC1 in rice, shows chlorophyll b reductase activity in vitro, phenotype, overview, a double mutant from a cross between nyc1-2 and a chlorophyll b-deficient mutant cao-2 does not show the stay-green senescence phenotype, overview
additional information
the non-yellow coloring, nyc1, recessive mutant is a rice stay-green phenotype mutant due to a defect in chlorophyl degradation, in which chlorophyll degradation during senescence is impaired, the mutant NYC1 does not show chlorophyll b reductase activity, but NOL, i.e. NYC1-like, a protein closely related to NYC1 in rice, shows chlorophyll b reductase activity in vitro, phenotype, overview, a double mutant from a cross between nyc1-2 and a chlorophyll b-deficient mutant cao-2 does not show the stay-green senescence phenotype, overview
additional information
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nyc1 mutant, shows the stay-green phenotype. Nol mutant (lines G079-11B, C130-10H and G087-9H) shows a stay-green phenotype very similar to that of the nyc1 mutant, i.e. the degradation of chlorophyll b is severely inhibited and light-harvesting complex II is selectively retained during senescence, resulting in the retention of thylakoid grana even at a late stage of senescence. The nyc1 nol double mutant does not show prominent enhancement of inhibition of chlorophyll degradation
additional information
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nyc1-mutant is a stay-green mutant. The double mutant nyc1/nol only slightly enhances the corresponding single mutant phenotypes
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