Weyandt Nicholas, Aghdam Shiva A, Brown Amanda M V
Department of Biological Sciences, Texas Tech University, Lubbock, TX, United States.
Front Microbiol. 2022 Apr 25;13:867392. doi: 10.3389/fmicb.2022.867392. eCollection 2022.
is a widespread endosymbiont of insects and filarial nematodes that profoundly influences host biology. has also been reported in rhizosphere hosts, where its diversity and function remain poorly characterized. The discovery that plant-parasitic nematodes (PPNs) host strains with unknown roles is of interest evolutionarily, ecologically, and for agriculture as a potential target for developing new biological controls. The goal of this study was to screen communities for PPN endosymbionts and analyze genes and genomic patterns that might indicate their role. Genome assemblies revealed 1 out of 16 sampled sites had nematode communities hosting a strain, designated Tex, that has highly diverged as one of the early supergroup L strains. Genome features, gene repertoires, and absence of known genes for cytoplasmic incompatibility, riboflavin, biotin, and other biosynthetic functions placed Tex between mutualist C + D strains and reproductive parasite A + B strains. Functional terms enriched in group L included protoporphyrinogen IX, thiamine, lysine, fatty acid, and cellular amino acid biosynthesis, while dN/dS analysis suggested the strongest purifying selection on arginine and lysine metabolism, and vitamin B6, heme, and zinc ion binding, suggesting these as candidate roles in PPN . Higher dN/dS pathways between group L, Pni from aphids, Fol from springtails, and CfeT from cat fleas suggested distinct functional changes characterizing these early host transitions. PPN had several putative horizontally transferred genes, including a lysine biosynthesis operon like that of the mitochondrial symbiont , a spirochete-like thiamine synthesis operon shared only with CfeT, an ATP/ADP carrier important in , and a eukaryote-like gene that may mediate plant systemic acquired resistance through the lysine-to-pipecolic acid system. The Discovery of group L-like variants from global rhizosphere databases suggests diverse PPN strains remain to be discovered. These findings support the hypothesis of plant-specialization as key to shaping early evolution and present new functional hypotheses, demonstrating promise for future genomics-based rhizosphere screens.
是昆虫和丝虫线虫广泛存在的内共生体，对宿主生物学有深远影响。在根际宿主中也有报道，但其多样性和功能仍知之甚少。植物寄生线虫（PPN）宿主携带作用未知的菌株这一发现，在进化、生态以及作为开发新生物防治潜在靶点的农业方面都具有重要意义。本研究的目的是筛选PPN内共生体群落，并分析可能表明其作用的基因和基因组模式。基因组组装显示，16个采样位点中有1个位点的线虫群落携带有一种菌株，命名为Tex，它作为早期超群L菌株之一高度分化。基因组特征、基因库以及缺乏细胞质不相容性、核黄素、生物素和其他生物合成功能的已知基因，使得Tex处于互利共生C + D菌株和生殖寄生虫A + B菌株之间。L组中富集的功能术语包括原卟啉原IX、硫胺素、赖氨酸、脂肪酸和细胞氨基酸生物合成，而dN/dS分析表明对精氨酸和赖氨酸代谢以及维生素B6、血红素和锌离子结合的纯化选择最强，表明这些是PPN中可能的作用。L组、蚜虫的Pni、跳虫的Fol和猫蚤的CfeT之间较高的dN/dS途径表明，这些早期宿主转变具有明显的功能变化。PPN有几个假定的水平转移基因，包括一个类似于线粒体共生体的赖氨酸生物合成操纵子、一个仅与CfeT共享的螺旋体样硫胺素合成操纵子、一个在[具体方面]重要的ATP/ADP载体，以及一个可能通过赖氨酸到哌啶酸系统介导植物系统获得性抗性的类真核生物基因。从全球根际数据库中发现类似L组的变体表明，仍有待发现多种PPN菌株。这些发现支持了植物特化是塑造早期[具体对象]进化关键的假设，并提出了新的功能假设，证明了未来基于基因组学的根际筛选的前景。
