Kimata-Ariga Y, Matsumura T, Kada S, Fujimoto H, Fujita Y, Endo T, Mano J, Sato F, Hase T
Division of Enzymology, Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka, 565-0871, Japan.
EMBO J. 2000 Oct 2;19(19):5041-50. doi: 10.1038/sj.emboj.7593319.
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.
在C4植物玉米（Zea mays L.）中，两种铁氧还蛋白同工型Fd I和Fd II分别在叶肉细胞和维管束鞘细胞中特异性表达。将这些铁氧还蛋白的cDNA分别导入具有破坏的内源性铁氧还蛋白基因的蓝细菌鞘丝藻（Plectonema boryanum）中，产生表达Fd I和Fd II的TM202和KM2 - 9菌株。TM202在高光（130微摩尔/平方米/秒）下生长受到抑制，而KM2 - 9以正常速率生长，但表现出缺氮表型。光合放氧的测量表明，在KM2 - 9中还原力没有有效地分配到氮同化中。在黑暗中使细胞饥饿后，远红光照射下TM202中P700的氧化水平显著增加。然而，KM2 - 9中的该水平保持较低，表明存在活跃的循环电子流。与此一致的是，与TM202相比，KM2 - 9中细胞的ATP/ADP比值增加，NADPH/NADP(+)比值降低。这些结果表明，两种细胞类型特异性铁氧还蛋白对光系统I周围的电子流有不同的调节作用。
