Abstract
Chloroplasts undergo drastic morphological and physiological changes during senescence with a visible symptom of chlorophyll (Chl) degradation. A stay green mutant was identified and then isolated from the japonica rice (Oryza sativa) cv. Huazhiwu by gamma-ray irradiation. The stay green mutant was characterized by Chl retention, stable Chl-protein complexes, and stable thylakoid membrane structures, but lost its photosynthetic competence during senescence. The gene, designated Stay Green Rice (SGR), was cloned by a positional cloning strategy encoding an ancient protein containing a putative chloroplast transit peptide. SGR protein was found in both soluble and thylakoid membranes in rice. SGR, like the gene for pheophorbide a oxygenase (PaO), was constitutively expressed, but was upregulated by dark-induced senescence in rice leaves. Senescence-induced expression of SGR and PaO was enhanced by ABA, but inhibited by cytokinin. Overexpression of SGR reduced the number of lamellae in the grana thylakoids and reduced the Chl content of normally growing leaves. This indicates that upregulation of SGR increases Chl breakdown during senescence in rice. A small quantity of chlorophyllide a accumulated in sgr leaves, but this also accumulated in wild-type rice leaves during senescence. Some pheophorbide a was detected in sgr leaves in the dark. According to these observations, we propose that SGR may be involved in regulating or taking part in the activity of PaO, and then may influence Chl breakdown and degradation of pigment-protein complex.
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Claims 14
Claim · model-written summary
A stay-green rice mutant was isolated by irradiation.
- Taxon
- rice
Oryza sativae0 - Material
- stay green mutante0
- Treatment
- gamma-ray irradiatione0
- Outcome
- stay green mutant was identified and then isolatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A stay green mutant was identified and then isolated from the japonica rice (Oryza sativa) cv. Huazhiwu by gamma-ray irradiation”
Claim · model-written summary
The mutant retained chlorophyll, chlorophyll-protein complexes and thylakoid structures.
- Taxon
- riceOryza sativat0
- Material
- stay green mutante0
- Outcome
- Chl retention, stable Chl-protein complexes, and stable thylakoid membrane structurese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The stay green mutant was characterized by Chl retention, stable Chl-protein complexes, and stable thylakoid membrane structures”
t0“rice”
Claim · model-written summary
The mutant lost photosynthetic competence during senescence.
- Taxon
- riceOryza sativat0
- Material
- stay green mutante1
- Outcome
- lost its photosynthetic competence during senescencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lost its photosynthetic competence during senescence”
e1“A stay green mutant was identified and then isolated from the japonica rice (Oryza sativa) cv. Huazhiwu by gamma-ray irradiation”
t0“stay green gene in rice”
Claim · model-written summary
SGR was cloned and encoded a protein with a putative chloroplast transit peptide.
- Taxon
- riceOryza sativat0
- Gene
- Stay Green Rice (SGR)e0
- Outcome
- cloned by a positional cloning strategy encoding an ancient protein containing a putative chloroplast transit peptidee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The gene, designated Stay Green Rice (SGR), was cloned by a positional cloning strategy encoding an ancient protein containing a putative chloroplast transit peptide”
t0“rice”
Claim · model-written summary
SGR protein occurred in soluble and thylakoid membranes.
- Taxon
- riceOryza sativae0
- Gene
- SGR proteine0
- Outcome
- found in both soluble and thylakoid membranese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SGR protein was found in both soluble and thylakoid membranes in rice”
Claim · model-written summary
SGR and PaO were constitutively expressed and upregulated in dark-induced senescence.
- Taxon
- riceOryza sativae0
- Organ / stage
- rice leavese0
- Gene
- SGRe0
- Outcome
- constitutively expressed, but was upregulated by dark-induced senescencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SGR, like the gene for pheophorbide a oxygenase (PaO), was constitutively expressed, but was upregulated by dark-induced senescence in rice leaves”
Claim · model-written summary
ABA enhanced senescence-induced expression of SGR and PaO.
- Taxon
- riceOryza sativat0
- Treatment
- ABAe0
- Gene
- SGR and PaOe0
- Outcome
- Senescence-induced expression of SGR and PaOe0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Senescence-induced expression of SGR and PaO was enhanced by ABA”
t0“rice”
Claim · model-written summary
Cytokinin inhibited senescence-induced expression of SGR and PaO.
- Taxon
- riceOryza sativat0
- Treatment
- cytokinine0
- Gene
- SGR and PaOe1
- Outcome
- Senescence-induced expression of SGR and PaOe1
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“inhibited by cytokinin”
e1“Senescence-induced expression of SGR and PaO was enhanced by ABA”
t0“Molecular cloning and function analysis of the stay green gene in rice”
Claim · model-written summary
SGR overexpression reduced grana thylakoid lamellae.
- Taxon
- riceOryza sativat0
- Treatment
- Overexpression of SGRe0
- Gene
- SGRe0
- Outcome
- number of lamellae in the grana thylakoidse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Overexpression of SGR reduced the number of lamellae in the grana thylakoids”
t0“rice”
Claim · model-written summary
SGR overexpression reduced chlorophyll content in normal leaves.
- Taxon
- riceOryza sativat0
- Treatment
- Overexpression of SGRe0
- Gene
- SGRe0
- Outcome
- Chl content of normally growing leavese0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Overexpression of SGR reduced the number of lamellae in the grana thylakoids and reduced the Chl content of normally growing leaves”
t0“rice”
Claim · model-written summary
A small amount of chlorophyllide a accumulated in mutant leaves.
- Taxon
- riceOryza sativat0
- Material
- sgre0
- Organ / stage
- leavese0
- Outcome
- A small quantity of chlorophyllide a accumulatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A small quantity of chlorophyllide a accumulated in sgr leaves”
t0“rice”
Claim · model-written summary
Chlorophyllide a also accumulated in wild-type rice leaves during senescence.
- Taxon
- riceOryza sativae0
- Material
- wild-type ricee0
- Organ / stage
- leavese0
- Outcome
- this also accumulatede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this also accumulated in wild-type rice leaves during senescence”
Claim · model-written summary
Pheophorbide a was detected in sgr leaves in darkness.
- Taxon
- riceOryza sativat0
- Material
- sgre0
- Organ / stage
- leavese0
- Outcome
- pheophorbide a was detectede0
- Qualifier
- in the darke0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Some pheophorbide a was detected in sgr leaves in the dark”
t0“rice”
Claim · model-written summary
The authors proposed that SGR may affect PaO activity and chlorophyll breakdown.
- Taxon
- riceOryza sativat0
- Gene
- SGRe0
- Outcome
- Chl breakdown and degradation of pigment-protein complexe0
- Qualifier
- activity of PaOe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“SGR may be involved in regulating or taking part in the activity of PaO, and then may influence Chl breakdown and degradation of pigment-protein complex”
t0“rice”
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