Abstract
Chlorophyll synthesis in barley is controlled by two different light-dependent NADPH:protochlorophyllide oxidoreductases, termed PORA and PORB. PORA is present abundantly in etioplasts but selectively disappears soon after the beginning of illumination. This negative light effect is mediated simultaneously at three different levels. First, the concentration of porA mRNA declines drastically during illumination of dark-grown seedlings. Second, the plastids' ability to import the precursor of PORA (pPORA) is reduced during the transition from etioplasts to chloroplasts. This effect is due to a rapid decline in the plastidic level of protochlorophyllide (Pchlide), which is required for the translocation of the pPORA. Third, PORA becomes selectively destabilized in illuminated seedlings. When illuminated, PORA-Pchlide-NADPH complexes formed in the dark photoreduce their Pchlide to Chlide and become simultaneously susceptible to attack by plastid proteases. The PORA-degrading protease activity is not detectable in etioplasts but is induced during illumination. In contrast to PORA, the second Pchlide-reducing enzyme, PORB, remains operative in both illuminated and green plants. Its translocation into plastids does not depend on its substrate, Pchlide.
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Claims 10
Claim · model-written summary
Two light-dependent oxidoreductases control chlorophyll synthesis in barley.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaree0 - Gene
- PORA and PORBe0
- Outcome
- Chlorophyll synthesise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Chlorophyll synthesis in barley is controlled by two different light-dependent NADPH:protochlorophyllide oxidoreductases, termed PORA and PORB.”
Claim · model-written summary
PORA is abundant in etioplasts and disappears after illumination begins.
- Taxon
- barleyHordeum vulgaree1
- Organ / stage
- etioplastse0
- Treatment
- illuminatione0
- Gene
- PORAe0
- Outcome
- selectively disappearse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PORA is present abundantly in etioplasts but selectively disappears soon after the beginning of illumination.”
e1“Chlorophyll synthesis in barley”
Claim · model-written summary
porA mRNA concentration declines drastically during illumination.
- Taxon
- barleyHordeum vulgaree1
- Treatment
- illuminatione0
- Gene
- porAe0
- Outcome
- concentration of porA mRNAe0
- Direction
- declinese0
- Comparator
- dark-grown seedlingse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the concentration of porA mRNA declines drastically during illumination of dark-grown seedlings”
e1“Chlorophyll synthesis in barley”
Claim · model-written summary
Plastid import of pPORA declines during the transition to chloroplasts.
- Taxon
- barleyHordeum vulgaree1
- Organ / stage
- etioplasts to chloroplastse0
- Gene
- PORAe0
- Outcome
- plastids' ability to import the precursor of PORAe0
- Direction
- reducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the plastids' ability to import the precursor of PORA (pPORA) is reduced during the transition from etioplasts to chloroplasts”
e1“Chlorophyll synthesis in barley”
Claim · model-written summary
A rapid decline of plastid protochlorophyllide mediates reduced pPORA translocation.
- Taxon
- barleyHordeum vulgaree1
- Compound
- protochlorophyllidee0
- Outcome
- translocation of the pPORAe0
- Direction
- declinee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This effect is due to a rapid decline in the plastidic level of protochlorophyllide (Pchlide), which is required for the translocation of the pPORA.”
e1“Chlorophyll synthesis in barley”
Claim · model-written summary
PORA becomes selectively destabilized in illuminated seedlings.
- Taxon
- barleyHordeum vulgaree1
- Treatment
- illuminatede0
- Gene
- PORAe0
- Outcome
- selectively destabilizede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PORA becomes selectively destabilized in illuminated seedlings.”
e1“Chlorophyll synthesis in barley”
Claim · model-written summary
Illuminated PORA complexes photoreduce Pchlide to Chlide and become susceptible to plastid proteases.
- Taxon
- barleyHordeum vulgaree1
- Gene
- PORAe0
- Outcome
- photoreduce their Pchlide to Chlidee0
- Qualifier
- susceptible to attack by plastid proteasese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PORA-Pchlide-NADPH complexes formed in the dark photoreduce their Pchlide to Chlide and become simultaneously susceptible to attack by plastid proteases.”
e1“Chlorophyll synthesis in barley”
Claim · model-written summary
PORA-degrading protease activity is induced by illumination and absent in etioplasts.
- Taxon
- barleyHordeum vulgaree1
- Treatment
- illuminatione0
- Gene
- PORA-degrading proteasee0
- Outcome
- protease activitye0
- Direction
- inducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The PORA-degrading protease activity is not detectable in etioplasts but is induced during illumination.”
e1“Chlorophyll synthesis in barley”
Claim · model-written summary
PORB remains operative in illuminated and green plants.
- Taxon
- barleyHordeum vulgaree1
- Gene
- PORBe0
- Outcome
- remains operativee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“PORB, remains operative in both illuminated and green plants.”
e1“Chlorophyll synthesis in barley”
Claim · model-written summary
PORB import into plastids does not depend on Pchlide.
- Taxon
- barleyHordeum vulgaree2
- Gene
- PORBe1
- Compound
- Pchlidee0
- Outcome
- translocation into plastidse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Its translocation into plastids does not depend on its substrate, Pchlide.”
e1“PORB, remains operative in both illuminated and green plants.”
e2“Chlorophyll synthesis in barley”
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