Differential electron flow around photosystem I by two C(4)-photosynthetic-cell-specific ferredoxins.
In the C(4) plant maize (Zea mays L.), two ferredoxin isoproteins, Fd I and Fd II, are expressed specifically in mesophyll and bundle-sheath cells, respectively. cDNAs for these ferredoxins were introduced separately into the cyanobacterium Plectonema boryanum with a disrupted endogenous ferredoxin gene, yielding TM202 and KM2-9 strains expressing Fd I and Fd II. The growth of TM202 was retarded under high light (130 micromol/m(2)/s), whereas KM2-9 grew at a normal rate but exhibited a nitrogen-deficient phenotype. Measurement of photosynthetic O(2) evolution revealed that the reducing power was not efficiently partitioned into nitrogen assimilation in KM2-9. After starvation of the cells in darkness, the P700 oxidation level under far-red illumination increased significantly in TM202. However, it remained low in KM2-9, indicating an active cyclic electron flow. In accordance with this, the cellular ratio of ATP/ADP increased and that of NADPH/NADP(+) decreased in KM2-9 as compared with TM202. These results demonstrated that the two cell type-specific ferredoxins differentially modulate electron flow around photosystem I.
Kimata-Ariga
Y
Y
Division of Enzymology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
Matsumura
T
T
Kada
S
S
Fujimoto
H
H
Fujita
Y
Y
Endo
T
T
Mano
J
J
Sato
F
F
Hase
T
T
D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015139:Blotting, Southern; D015153:Blotting, Western; D002352:Carrier Proteins; D002734:Chlorophyll / Q000378:metabolism; D000458:Cyanobacteria / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D004579:Electron Transport; D005288:Ferredoxins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008027:Light; D045342:Light-Harvesting Protein Complexes; D016297:Mutagenesis, Site-Directed; D009249:NADP / Q000378:metabolism; D017672:Nitrogen Compounds / Q000378:metabolism; D010084:Oxidation-Reduction; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000378:metabolism*; D045331:Photosystem I Protein Complex; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction; D014170:Transformation, Genetic; D003313:Zea mays / Q000235:genetics*
D001426:Bacterial Proteins; D002352:Carrier Proteins; D005288:Ferredoxins; D045342:Light-Harvesting Protein Complexes; D017672:Nitrogen Compounds; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D009249:NADP; C001785:chlorophyll P 700; D000255:Adenosine Triphosphate