Abstract
Malate dehydrogenases (MDHs) convert malate to oxaloacetate using NAD(H) or NADP(H) as a cofactor. Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype. The reason for these severe phenotypes is unknown. Here, we rescued the embryo lethality of pdnad-mdh via embryo-specific expression of pdNAD-MDH. Rescued seedlings developed white leaves with aberrant chloroplasts and failed to reproduce. Inducible silencing of pdNAD-MDH at the rosette stage also resulted in white newly emerging leaves. These data suggest that pdNAD-MDH is important for early plastid development, which is consistent with the reductions in major plastidial galactolipid, carotenoid, and protochlorophyllide levels in miR-mdh-1 seedlings. Surprisingly, the targeting of other NAD-dependent MDH isoforms to the plastid did not complement the embryo lethality of pdnad-mdh, while expression of enzymatically inactive pdNAD-MDH did. These complemented plants grew indistinguishably from the wild type. Both active and inactive forms of pdNAD-MDH interact with a heteromeric AAA-ATPase complex at the inner membrane of the chloroplast envelope. Silencing the expression of FtsH12, a key member of this complex, resulted in a phenotype that strongly resembles miR-mdh-1. We propose that pdNAD-MDH is essential for chloroplast development due to its moonlighting role in stabilizing FtsH12, distinct from its enzymatic function.
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Claims 10
Claim · model-written summary
Embryo-specific pdNAD-MDH expression rescued pdnad-mdh embryo lethality.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae1 - Treatment
- embryo-specific expression of pdNAD-MDHe0
- Gene
- pdNAD-MDHe0
- Outcome
- embryo lethalitye0
- Direction
- rescuede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Here, we rescued the embryo lethality of pdnad-mdh via embryo-specific expression of pdNAD-MDH.”
e1“Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype.”
Claim · model-written summary
Rescued seedlings had white leaves, aberrant chloroplasts and failed reproduction.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Outcome
- white leaves with aberrant chloroplasts and failed to reproducee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rescued seedlings developed white leaves with aberrant chloroplasts and failed to reproduce.”
e1“Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype.”
Claim · model-written summary
Rosette-stage pdNAD-MDH silencing produced white emerging leaves.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- Inducible silencing of pdNAD-MDHe0
- Gene
- pdNAD-MDHe0
- Outcome
- white newly emerging leavese0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Inducible silencing of pdNAD-MDH at the rosette stage also resulted in white newly emerging leaves.”
e1“Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype.”
Claim · model-written summary
miR-mdh-1 seedlings had reduced galactolipid, carotenoid and protochlorophyllide levels.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Material
- miR-mdh-1e0
- Outcome
- major plastidial galactolipid, carotenoid, and protochlorophyllide levelse0
- Direction
- reductionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reductions in major plastidial galactolipid, carotenoid, and protochlorophyllide levels in miR-mdh-1 seedlings.”
e1“Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype.”
Claim · model-written summary
Other plastid-targeted NAD-dependent MDH isoforms did not rescue embryo lethality.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- targeting of other NAD-dependent MDH isoforms to the plastide0
- Outcome
- embryo lethalitye0
- Direction
- did not complemente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the targeting of other NAD-dependent MDH isoforms to the plastid did not complement the embryo lethality of pdnad-mdh”
e1“Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype.”
Claim · model-written summary
Enzymatically inactive pdNAD-MDH rescued embryo lethality.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- expression of enzymatically inactive pdNAD-MDHe0
- Gene
- pdNAD-MDHe0
- Outcome
- complemented plantse0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“expression of enzymatically inactive pdNAD-MDH did. These complemented plants grew indistinguishably from the wild type.”
e1“Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype.”
Claim · model-written summary
Complemented plants grew like wild type.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Outcome
- grew indistinguishablye0
- Direction
- indistinguishablye0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These complemented plants grew indistinguishably from the wild type.”
e1“Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype.”
Claim · model-written summary
Active and inactive pdNAD-MDH interacted with a chloroplast envelope AAA-ATPase complex.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- pdNAD-MDHe0
- Outcome
- interact with a heteromeric AAA-ATPase complexe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both active and inactive forms of pdNAD-MDH interact with a heteromeric AAA-ATPase complex at the inner membrane of the chloroplast envelope.”
e1“Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype.”
Claim · model-written summary
FtsH12 silencing produced a phenotype resembling miR-mdh-1.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- Silencing the expression of FtsH12e0
- Gene
- FtsH12e0
- Outcome
- a phenotype that strongly resembles miR-mdh-1e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Silencing the expression of FtsH12, a key member of this complex, resulted in a phenotype that strongly resembles miR-mdh-1.”
e1“Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype.”
Claim · model-written summary
The authors propose pdNAD-MDH stabilizes FtsH12 to support chloroplast development.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- pdNAD-MDHe0
- Outcome
- chloroplast developmente0
- Qualifier
- stabilizing FtsH12e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We propose that pdNAD-MDH is essential for chloroplast development due to its moonlighting role in stabilizing FtsH12, distinct from its enzymatic function.”
e1“Arabidopsis thaliana mutants lacking plastidial NAD-dependent MDH (pdnad-mdh) are embryo-lethal, and constitutive silencing (miR-mdh-1) causes a pale, dwarfed phenotype.”
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