Paul Blair G, Bagby Sarah C, Czornyj Elizabeth, Arambula Diego, Handa Sumit, Sczyrba Alexander, Ghosh Partho, Miller Jeff F, Valentine David L
Marine Science Institute, University of California, Santa Barbara, California 93106, USA.
Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, California 90095, USA.
Nat Commun. 2015 Mar 23;6:6585. doi: 10.1038/ncomms7585.
In the evolutionary arms race between microbes, their parasites, and their neighbours, the capacity for rapid protein diversification is a potent weapon. Diversity-generating retroelements (DGRs) use mutagenic reverse transcription and retrohoming to generate myriad variants of a target gene. Originally discovered in pathogens, these retroelements have been identified in bacteria and their viruses, but never in archaea. Here we report the discovery of intact DGRs in two distinct intraterrestrial archaeal systems: a novel virus that appears to infect archaea in the marine subsurface, and, separately, two uncultivated nanoarchaea from the terrestrial subsurface. The viral DGR system targets putative tail fibre ligand-binding domains, potentially generating >10(18) protein variants. The two single-cell nanoarchaeal genomes each possess ≥4 distinct DGRs. Against an expected background of low genome-wide mutation rates, these results demonstrate a previously unsuspected potential for rapid, targeted sequence diversification in intraterrestrial archaea and their viruses.
在微生物、其寄生虫及其邻居之间的进化军备竞赛中，快速蛋白质多样化的能力是一种强大的武器。多样性产生反转录元件（DGRs）利用诱变逆转录和逆转归巢来产生靶基因的无数变体。这些反转录元件最初在病原体中被发现，已在细菌及其病毒中得到鉴定，但从未在古菌中发现过。在此，我们报告在两个不同的陆地古菌系统中发现了完整的DGRs：一种似乎感染海洋次表层古菌的新型病毒，以及分别来自陆地次表层的两种未培养的纳米古菌。病毒DGR系统靶向假定的尾纤维配体结合结构域，可能产生>10¹⁸种蛋白质变体。这两个单细胞纳米古菌基因组各自拥有≥4个不同的DGRs。鉴于全基因组突变率较低这一预期背景，这些结果证明了陆地古菌及其病毒中存在此前未被怀疑的快速、靶向序列多样化的潜力。
