Diverse Phage-Encoded Toxins in a Protective Insect Endosymbiont
Diverse Phage-Encoded Toxins in a Protective Insect Endosymbiont
复制标题
DOI：
10.1128/aem.01285-08
复制
发表时间：
2008-11-01
影响因子：
4.4
通讯作者：
Moran, Nancy A.
中科院分区：
文献类型：
--
作者：
Degnan, Patrick H.;Moran, Nancy A.
溶原性噬菌体APSE感染蚜虫和其他以汁液为食的昆虫的兼性内共生体“防御Hamiltonella”。这种内共生体与蚜虫建立了有益的联系，增加了寄生蜂攻击后的存活率。虽然APSE和“Ca。防御汉米尔顿菌在蚜虫世代间通过母系有效地传播，但也可以在昆虫寄主间水平传播，从而导致遗传上不同的防御汉米尔顿菌。防御汉密尔顿氏体”菌株感染同一种蚜虫，APSE和“Ca.防御汉米尔顿菌”的宿主。蚜虫只感染了“钙。防御汉密尔顿氏菌”比感染这两种病毒的人保护作用明显更小“。防御汉密尔顿氏菌”和APSE。这种保护已经被提出与先前在两种特征性APSE菌株的基因组中发现的真核生物靶向毒素有关。在这项研究中，我们已经从另外七个APSE菌株的部分基因组测序，以解决这个噬菌体中毒素变异的演变和程度。APSE裂解区已成为新型毒力盒非同源重组的热点。我们从三个蛋白质家族中鉴定了四种新的毒素，志贺样毒素，细胞致死膨胀毒素和YD重复毒素。这些重组事件也导致下游溶菌酶和holin基因的重配。保守的APSE基因侧翼的可变毒素盒的分析揭示了一个密切的系统发育相关的噬菌体序列从其他两个兼性内共生昆虫。因此，噬菌体可以作为一个管道进行基因交换之间的遗传内共生体。
The lysogenic bacteriophage APSE infects "Candidatus Hamiltonella defensa," a facultative endosymbiont of aphids and other sap-feeding insects. This endosymbiont has established a beneficial association with aphids, increasing survivorship following attack by parasitoid wasps. Although APSE and "Ca. Hamiltonella defensa" are effectively maternally transmitted between aphid generations, they can also be horizontally transferred among insect hosts, which results in genetically distinct "Ca. Hamiltonella defensa" strains infecting the same aphid species and sporadic distributions of both APSE and "Ca. Hamiltonella defensa" among hosts. Aphids infected only with "Ca. Hamiltonella defensa" have significantly less protection than those infected with both "Ca. Hamiltonella defensa" and APSE. This protection has been proposed to be connected to eukaryote-targeted toxins previously discovered in the genomes of two characterized APSE strains. In this study, we have sequenced partial genomes from seven additional APSE strains to address the evolution and extent of toxin variation in this phage. The APSE lysis region has been a hot spot for nonhomologous recombination of novel virulence cassettes. We identified four new toxins from three protein families, Shiga-like toxin, cytolethal distending toxin, and YD-repeat toxins. These recombination events have also resulted in reassortment of the downstream lysozyme and holin genes. Analysis of the conserved APSE genes flanking the variable toxin cassettes reveals a close phylogenetic association with phage sequences from two other facultative endosymbionts of insects. Thus, phage may act as a conduit for ongoing gene exchange among heritable endosymbionts.