Phosphoenolpyruvate carboxykinase in the C4 monocot Urochloa panicoides is encoded by four differentially expressed genes
Phosphoenolpyruvate carboxykinase in the C4 monocot Urochloa panicoides is encoded by four differentially expressed genes
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DOI：
10.1104/pp.120.4.1033
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发表时间：
1999-08-01
期刊：
影响因子：
7.4
通讯作者：
Burnell, JN
中科院分区：
文献类型：
--
作者：
Finnegan, PM;Suzuki, S;Burnell, JN
早先通过对草履虫叶片聚(A(+))RNA文库的筛选，获得了编码草履虫PCK亚单位PCK1的cDNAs。通过重新筛选文库，现在已经发现了第二个PCK序列，命名为PCK2。推导出的PCK2多肽全长626个残基，预测分子质量为68686D，与推导的PCK1序列有96%的同源性。基因组DNA片段的分离和鉴定表明，PCK1和PCK2基因分别与另一个PCK基因紧密连锁。这些额外的基因分别被命名为PCK3和PCK4。在每种情况下，第二个基因都位于上游，与通过cdna分析确定的基因具有相同的转录方向。逆转录-聚合酶链式反应分析表明，PCK1和PCK2的转录本在叶片中占优势，而PCK3和PCK4的转录本在根中占优势。此外，PCK1和PCK2转录本的积累是光依赖的。对从叶片中纯化的PCK多肽的N末端直接测序表明，PCK2是产生的。这些结果有力地表明，PCK1和PCK2参与了盘根草的光合作用CO2浓缩机制。
Previous screening of a cDNA library of leaf poly(A(+)) RNA from Urochloa panicoides, a phosphoenolpyruvate carboxykinase (PCK)-type C-4 monocot, led to the characterization of cDNAs encoding the U. panicoides PCK subunit PCK1. A second PCK sequence, designated PCK2, has now been found by rescreening the library. The deduced PCK2 polypeptide is 626 residues in length, has a predicted molecular mass of 68,686 D, and is 96% identical to the deduced PCK1 sequence. Isolation and characterization of genomic DNA fragments revealed that the PCK1 and PCK2 genes are each closely linked to another PCK gene. These additional genes have been designated PCK3 and PCK4, respectively. In each case, the second gene is located upstream and in the same transcriptional orientation as the gene characterized through cDNA analysis. A reverse transcription-polymerase chain reaction assay was used to demonstrate that PCK1 and PCK2 transcripts predominate in leaves, whereas PCK3 and PCK4 transcripts predominate in roots. Moreover, accumulation of PCK1 and PCK2 transcripts is light dependent. Direct N-terminal sequencing of PCK polypeptides purified from leaves demonstrated that PCK2 is produced. These results strongly suggest that PCK1 and PCK2 are involved in the photosynthetic CO2-concentrating mechanism active in U. panicoides.