Woolfit Megan, Iturbe-Ormaetxe Iñaki, Brownlie Jeremy C, Walker Thomas, Riegler Markus, Seleznev Andrei, Popovici Jean, Rancès Edwige, Wee Bryan A, Pavlides Jennifer, Sullivan Mitchell J, Beatson Scott A, Lane Amanda, Sidhu Manpreet, McMeniman Conor J, McGraw Elizabeth A, O'Neill Scott L
School of Biological Sciences, Monash University, Clayton, Victoria, Australia.
Genome Biol Evol. 2013;5(11):2189-204. doi: 10.1093/gbe/evt169.
Most strains of the widespread endosymbiotic bacterium Wolbachia pipientis are benign or behave as reproductive parasites. The pathogenic strain wMelPop is a striking exception, however: it overreplicates in its insect hosts and causes severe life shortening. The mechanism of this pathogenesis is currently unknown. We have sequenced the genomes of three variants of wMelPop and of the closely related nonpathogenic strain wMelCS. We show that the genomes of wMelCS and wMelPop appear to be identical in the nonrepeat regions of the genome and differ detectably only by the triplication of a 19-kb region that is unlikely to be associated with life shortening, demonstrating that dramatic differences in the host phenotype caused by this endosymbiont may be the result of only minor genetic changes. We also compare the genomes of the original wMelPop strain from Drosophila melanogaster and two sequential derivatives, wMelPop-CLA and wMelPop-PGYP. To develop wMelPop as a novel biocontrol agent, it was first transinfected into and passaged in mosquito cell lines for approximately 3.5 years, generating wMelPop-CLA. This cell line-passaged strain was then transinfected into Aedes aegypti mosquitoes, creating wMelPop-PGYP, which was sequenced after 4 years in the insect host. We observe a rapid burst of genomic changes during cell line passaging, but no further mutations were detected after transinfection into mosquitoes, indicating either that host preadaptation had occurred in cell lines, that cell lines are a more selectively permissive environment than animal hosts, or both. Our results provide valuable data on the rates of genomic and phenotypic change in Wolbachia associated with host shifts over short time scales.
广泛存在的内共生细菌沃尔巴克氏体（Wolbachia pipientis）的大多数菌株是良性的，或表现为生殖寄生虫。然而，致病菌株wMelPop是一个显著的例外：它在昆虫宿主中过度复制并导致严重的寿命缩短。目前尚不清楚这种发病机制。我们已经对wMelPop的三个变体以及密切相关的非致病菌株wMelCS的基因组进行了测序。我们发现，wMelCS和wMelPop的基因组在基因组的非重复区域似乎是相同的，仅在一个不太可能与寿命缩短相关的19 kb区域发生了三倍复制，这表明这种内共生菌引起的宿主表型的巨大差异可能只是微小基因变化的结果。我们还比较了来自黑腹果蝇的原始wMelPop菌株及其两个连续衍生物wMelPop-CLA和wMelPop-PGYP的基因组。为了将wMelPop开发成一种新型生物防治剂，它首先被转染到蚊子细胞系中并传代约3.5年，产生了wMelPop-CLA。然后将这个细胞系传代菌株转染到埃及伊蚊中，创建了wMelPop-PGYP，它在昆虫宿主中培养4年后进行了测序。我们观察到在细胞系传代过程中基因组变化迅速爆发，但在转染到蚊子中后未检测到进一步的突变，这表明要么在细胞系中发生了宿主预适应，要么细胞系是比动物宿主更具选择性的宽松环境，或者两者皆是。我们的结果提供了关于沃尔巴克氏体在短时间尺度上与宿主转移相关的基因组和表型变化速率的有价值数据。
