Brown Amanda M V, Wasala Sulochana K, Howe Dana K, Peetz Amy B, Zasada Inga A, Denver Dee R
Department of Biological Sciences, Texas Tech University, Lubbock, TX, United States.
Department of Integrative Biology, Oregon State University, Corvallis, OR, United States.
Front Microbiol. 2018 Oct 16;9:2482. doi: 10.3389/fmicb.2018.02482. eCollection 2018.
and are among the most important and widespread of all endosymbionts, occurring in nematodes and more than half of insect and arachnid species, sometimes as coinfections. These symbionts are of significant interest as potential biocontrol agents due to their abilities to cause major effects on host biology and reproduction through cytoplasmic incompatibility, sex ratio distortion, or obligate mutualism. The ecological and metabolic effects of coinfections are not well understood. This study examined a - coinfection in the plant-parasitic nematode (PPN), , producing the first detailed study of such a coinfection using fluorescence hybridization (FISH), polymerase chain reaction (PCR), and comparative genomic analysis. Results from FISH and single-nematode PCR showed 123/127 individuals in a focal population carried (denoted strain cPpe), and 48% were coinfected with strain wPpe. Both endosymbionts showed dispersed tissue distribution with highest densities in the anterior intestinal walls and gonads. Phylogenomic analyses confirmed an early place of cPpe and long distance from a sister strain in another PPN, , supporting a long history of both and in PPNs. The genome of cPpe was 1.36 Mbp with 35.8% GC content, 1,131 predicted genes, 41% having no known function, and missing biotin and lipoate synthetic capacity and a plasmid present in other strains, despite having a slightly larger genome compared to other sequenced . The larger genome revealed expansions of gene families likely involved in host-cellular interactions. More than 2% of the genes of cPpe and wPpe were identified as candidate horizontally transferred genes, with some of these from eukaryotes, including nematodes. A model of the possible - interaction is proposed with possible complementation in function for pathways such as methionine and fatty acid biosynthesis and biotin transport.
[具体共生菌名称1]和[具体共生菌名称2]是所有内共生体中最重要且分布最广泛的，存在于线虫以及超过半数的昆虫和蛛形纲物种中，有时会同时感染。由于这些共生体能够通过细胞质不相容性、性别比例扭曲或专性互利共生对宿主生物学和繁殖产生重大影响，因此作为潜在的生物防治剂备受关注。同时感染的生态和代谢影响尚未得到充分了解。本研究检测了植物寄生线虫（PPN）[具体线虫名称]中的[具体共生菌名称1] - [具体共生菌名称2]同时感染情况，首次利用荧光原位杂交（FISH）、聚合酶链反应（PCR）和比较基因组分析对这种同时感染进行了详细研究。FISH和单线虫PCR结果显示，在一个重点群体中，127个个体中有123个携带[具体共生菌名称1]（记为cPpe菌株），48%同时感染了wPpe菌株。两种内共生体在组织中均呈分散分布，在前肠壁和性腺中的密度最高。系统基因组分析证实cPpe处于早期位置，与另一种PPN中的姐妹菌株距离较远，这支持了[具体共生菌名称1]和[具体共生菌名称2]在PPN中存在悠久历史。cPpe的基因组为1.36 Mbp，GC含量为35.8%，有1131个预测基因，41%的基因功能未知，且缺乏生物素和硫辛酸合成能力以及其他菌株中存在的质粒，尽管其基因组相比其他已测序的[具体共生菌名称]略大。更大的基因组揭示了可能参与宿主 - 细胞相互作用的基因家族的扩张。cPpe和wPpe中超过2%的基因被鉴定为候选水平转移基因，其中一些来自真核生物，包括线虫。提出了一种可能的[具体共生菌名称1] - [具体共生菌名称2]相互作用模型，在甲硫氨酸和脂肪酸生物合成以及生物素转运等途径中可能存在功能互补。
