Co-evolution between an Endosymbiont and Its Nematode Host: Wolbachia Asymmetric Posterior Localization and AP Polarity Establishment

Sullivan W (2014) Co-evolution between an Endosymbiont and Its Nematode Host: Wolbachia Asymmetric Posterior Localization and AP Polarity Establishment. PLoS Negl Trop Dis 8(8): e3096. doi:10.1371/journal.pntd.0003096 Co-evolution between an Endosymbiont and Its Nematode Host: Wolbachia Asymmetric Posterior Localization and AP Polarity Establishment Frederic Landmann 0 Jeremy M. Foster 0 Michelle L. Michalski 0 Barton E. Slatko 0 William Sullivan 0 Benjamin L. Makepeace, University of Liverpool, United Kingdom 0 1 Department of Molecular, Cell and Developmental Biology, Sinsheimer Labs, University of California, Santa Cruz, California, United States of America, 2 Centre de Recherche de Biochimie Macromole culaire, CNRS, Montpellier, France , 3 Molecular Parasitology, New England Biolabs, Ipswich , Massachusetts, United States of America, 4 Department of Biology and Microbiology, University of Wisconsin Oshkosh , Oshkosh, Wisconsin , United States of America While bacterial symbionts influence a variety of host cellular responses throughout development, there are no documented instances in which symbionts influence early embryogenesis. Here we demonstrate that Wolbachia, an obligate endosymbiont of the parasitic filarial nematodes, is required for proper anterior-posterior polarity establishment in the filarial nematode B. malayi. Characterization of pre- and post-fertilization events in B. malayi reveals that, unlike C. elegans, the centrosomes are maternally derived and produce a cortical-based microtubule organizing center prior to fertilization. We establish that Wolbachia rely on these cortical microtubules and dynein to concentrate at the posterior cortex. Wolbachia also rely on PAR-1 and PAR-3 polarity cues for normal concentration at the posterior cortex. Finally, we demonstrate that Wolbachia depletion results in distinct anterior-posterior polarity defects. These results provide a striking example of endosymbiont-host co-evolution operating on the core initial developmental event of axis determination. - Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files. Funding: This work has been funded from a NSF grant (MCB-1122252) and New England Biolabs (http://www.nsf.gov, https://www.neb.com). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: BES and JMF are employed by New England Biolabs Inc. This does not alter our adherence to all PLOS NTDs policies on sharing data and materials. The phylum Nematoda comprises up to 1 million species and is one of the most diverse and successful, with members colonizing all possible ecological niches on earth [1,2]. Nematodes have an extraordinary ability to adapt to the parasitic life style [36] and as a result exert profound impacts on agriculture and human health. The Spirurina clade contains only animal parasites, among them the Onchocercidae or filarial nematodes [5]. These thread-like worms are tissue-dwelling parasites, transmitted by arthropods, usually black flies or mosquitoes, to all classes of vertebrates except fish. It is estimated that 150 million people are infected with filarial nematodes, with 1 billion living at risk in tropical areas. Filarial nematodes lead to debilitating diseases such as onchocerciasis (caused by Onchocerca volvulus) and lymphatic filariasis (Brugia malayi, Brugia timori, Wuchereria bancrofti) [7]. A total of eight species of filarial nematodes are responsible for these neglected tropical diseases. With the exception of Loa and certain Mansonella sp., all other human filariae harbor an alphaproteobacterium of the genus Wolbachia. This symbiosis is restricted to the family of Onchocercidae among nematodes [7,8]. In addition, Wolbachia are also widespread among arthropods [9] and the bacteria of this genus have been classified into different supergroups, as defined by MultiLocus Sequence Typing [10,11]. The supergroups C and D represent the majority of Wolbachia in filarial species and are restricted to the Onchocercidae [8]. Wolbachia are required for filarial nematode fertility and survival [12] and we previously showed that removal of either supergroup C or D bacteria by antibiotic therapies against O. volvulus or B. malayi leads to extensive apoptosis [13]. Yet little is known about the actual basis of the mutualistic interaction. Genomic analysis and experimental studies suggest that Wolbachia may contribute to metabolic pathways absent or partially missing in the nematode host, including synthesis of riboflavin, nucleotides and hemes [1416]. However, the recent publication of the Loa genome, a Wolbachia-free human filarial parasite, revealed no metabolic compensation for the lack of mutualistic endosymbionts, suggesting caution in drawing conclusions on the basis of the symbiosis from genomic studies [17]. In the vast majority of filarial species, Wolbachia are present in the hypodermal chords of both male and female adult specimens, and in the female germline [8]. This is achieved through both asymmetric segregation during the mitotic divisions and cell-to-cell migration [18]. Immediately following fertilization, Wolbachia concentrate at the posterior region of the embryo. Wolbachia first localize in the posterior germline precursor lineage by rounds of asymmetric segregation until the 12-cell stage. They then reach a Filarial nematodes are responsible for a number of neglected tropical diseases. The vast majority of these human parasites harbor the bacterial endosymbiont Wolbachia. Wolbachia are essential for filarial nematode survival and reproduction, and thus are a promising antifilarial drug target. Understanding the molecular and cellular basis of Wolbachia-nematode interactions will facilitate the development of a new class of drugs that specifically disrupt these interactions. Here we focus on Wolbachia segregation patterns and interactions with the host cytoskeleton during early embryogenesis. Our studies indicate that centrosomes are maternally inherited in filarial nematodes resulting in a posterior microtubuleorganizing center of maternal origin, unique to filarial nematodes. This microtubule-organizing center facilitates the concentration of Wolbachia at the posterior pole. We find that the microtubule motor dynein is required for the proper posterior Wolbachia localization. In addition, we demonstrate that Wolbachia rely on polarity signals in the egg for their preferential localization at the posterior pole. Conversely, Wolbachia are required for normal embryonic axis determination and Wolbachia removal leads to distinct anterior-posterior embryonic polarity defects. To our knowledge, this is the first example of a bacterial endosymbiont required for normal host embryogenesis. hypodermal lineage, and from this subset of pos (...truncated)