Anderson S L, McIntosh L
DOE Plant Research Laboratory, Michigan State University, East Lansing 48824.
Plant Mol Biol. 1991 Apr;16(4):487-99. doi: 10.1007/BF00023416.
The psaC gene, which encodes the 8.9 kDa iron-sulfur containing subunit of Photosystem I, has been sequenced from Synechocystis sp. PCC 6803 and shows greater similarity to reported plant sequences than other cyanobacterial psaC sequences. The deduced amino acid sequence of the protein encoded by the Synechocystis psaC gene is identical to the tobacco PSA-C sequence. In plants psaC is located in the small single-copy region of the chloroplast genome between two genes (designated ndhE and ndhD) with similarity to genes encoding subunits of the mitochondrial NADH Dehydrogenase Complex I. The 5' ndhE-psaC-ndhD3' gene arrangement of higher plants is only partially conserved in Synechocystis. An open reading frame (ORF) upstream of the Synechocystis psaC gene has 85% identity to the tobacco ndhE gene. Downstream of psaC there is a 273 bp ORF with 48% identity to the 5' portion of the tobacco ndhD gene (1527 bp). psaC, ndhE and the region of similarity to ndhD are present in a single copy in the Synechocystis genome. Part of the wheat ndhD gene was sequenced and used as a probe for the presence of the 3' portion of the ndhD gene. The wheat ndhD probe did not hybridize to Synechocystis or Anabaena sp. PCC 7120 genomic DNA, but did hybridize to Oenothera chloroplast DNA. These results indicate the complete ndhD gene is absent in two cyanobacteria, and raises the question of what role, if any, the ndhD gene product plays in the facultative heterotroph Synechocystis sp. PCC 6803.
编码光系统I中含8.9 kDa铁硫亚基的psaC基因，已从集胞藻属PCC 6803中测序得到，与已报道的植物序列相比，它与其他蓝藻psaC序列具有更高的相似性。集胞藻psaC基因编码的蛋白质推导氨基酸序列与烟草PSA - C序列相同。在植物中，psaC位于叶绿体基因组的小单拷贝区域，在两个与线粒体NADH脱氢酶复合体I亚基编码基因相似的基因（命名为ndhE和ndhD）之间。高等植物的5' ndhE - psaC - ndhD3'基因排列在集胞藻中仅部分保守。集胞藻psaC基因上游的一个开放阅读框（ORF）与烟草ndhE基因有85%的同一性。在psaC下游有一个273 bp的ORF，与烟草ndhD基因（1527 bp）的5'部分有48%的同一性。psaC、ndhE以及与ndhD相似的区域在集胞藻基因组中以单拷贝形式存在。对小麦ndhD基因的一部分进行了测序，并用作探测ndhD基因3'部分存在情况的探针。小麦ndhD探针未与集胞藻或鱼腥藻属PCC 7120基因组DNA杂交，但与月见草叶绿体DNA杂交。这些结果表明，在两种蓝藻中不存在完整的ndhD基因，并提出了ndhD基因产物在兼性异养集胞藻属PCC 6803中是否起作用（如果有作用的话）的问题。
