Lai C Y, Baumann P, Moran N A
Microbiology Section, University of California, Davis 95616-8665, USA.
Insect Mol Biol. 1995 Feb;4(1):47-59. doi: 10.1111/j.1365-2583.1995.tb00007.x.
Two DNA fragments (3941 and 7152 base pairs) from the procaryotic endosymbiont (Buchnera) of the aphid Schlechtendalia chinensis were cloned and sequenced. The smaller fragment contained trpEG and the larger fragment contained trpDC(F)BA, genes coding for enzymes of the tryptophan biosynthetic pathway which convert chorismate to tryptophan. Both of these gene clusters were present as one copy on the endosymbiont chromosome and probably constitute two transcription units. The deduced amino acid sequences of the proteins was 51-61% identical to the corresponding proteins were previously studied in Buchnera of the aphid Schizaphis graminum. In this endosymbiont, trpEG is amplified and located on a plasmid, whereas, in the endosymbiont of S. chinensis, as in other eubacteria, trpEG occurs as a single copy on the bacterial chromosome. Implications of these findings for the evolution of this mutualistic association are discussed.
克隆并测序了来自中华蚱蜢内共生菌（布赫纳氏菌）的两个DNA片段（3941和7152个碱基对）。较小的片段包含trpEG，较大的片段包含trpDC(F)BA，这些基因编码色氨酸生物合成途径中从分支酸转化为色氨酸的酶。这两个基因簇在内共生菌染色体上均以单拷贝形式存在，可能构成两个转录单元。推导的蛋白质氨基酸序列与先前在麦二叉蚜布赫纳氏菌中研究的相应蛋白质有51%-61%的同一性。在这种内共生菌中，trpEG被扩增并位于一个质粒上，而在中华蚱蜢的内共生菌中，与其他真细菌一样，trpEG以单拷贝形式存在于细菌染色体上。讨论了这些发现对这种共生关系进化的影响。
