The bacterial endosymbiont Wolbachia manipulates arthropod reproduction to facilitate its maternal spread through host populations. The most common manipulation is cytoplasmic incompatibility (CI): Wolbachia-infected males produce modified sperm that cause embryonic mortality, unless rescued by embryos harboring the same Wolbachia. The genes underlying CI, cifA and cifB, were recently identified in the eukaryotic association module of Wolbachia’s prophage WO. Here, we use transcriptomic and genomic approaches to address three important evolutionary facets of the cif genes. First, we assess whether or not cifA and cifB comprise a classic toxin–antitoxin operon in wMel and show that the two genes exhibit striking, transcriptional differences across host development. They can produce a bicistronic message despite a predicted hairpin termination element in their intergenic region. Second, cifA and cifB strongly coevolve across the diversity of phage WO. Third, we provide new domain and functional predictions across homologs within Wolbachia, and show that amino acid sequences vary substantially across the genus. Finally, we investigate conservation of cifA and cifB and find frequent degradation and loss of the genes in strains that no longer induce CI. Taken together, we demonstrate that cifA and cifB exhibit complex transcriptional regulation in wMel, provide functional annotations that broaden the potential mechanisms of CI induction, and report recurrent erosion of cifA and cifB in non-CI strains, thus expanding our understanding of the most widespread form of reproductive parasitism.
Chemoautotrophic endosymbionts are the metabolic cornerstone of hydrothermal vent communities, providing invertebrate hosts with nearly all of their nutrition. The Calyptogena magnifica (Bivalvia: Vesicomyidae) symbiont, Candidatus Ruthia magnifica , is the first intracellular sulfur-oxidizing endosymbiont to have its genome sequenced, revealing a suite of metabolic capabilities. The genome encodes major chemoautotrophic pathways as well as pathways for biosynthesis of vitamins, cofactors, and all 20 amino acids required by the clam.
As pollinators, bees are cornerstones for terrestrial ecosystem stability and key components in agricultural productivity. All animals, including bees, are associated with a diverse community of microbes, commonly referred to as the microbiome. The bee microbiome is likely to be a crucial factor affecting host health. However, with the exception of a few pathogens, the impacts of most members of the bee microbiome on host health are poorly understood. Further, the evolutionary and ecological forces that shape and change the microbiome are unclear. Here, we discuss recent progress in our understanding of the bee microbiome, and we present challenges associated with its investigation. We conclude that global coordination of research efforts is needed to fully understand the complex and highly dynamic nature of the interplay between the bee microbiome, its host, and the environment. High-throughput sequencing technologies are ideal for exploring complex biological systems, including host-microbe interactions. To maximize their value and to improve assessment of the factors affecting bee health, sequence data should be archived, curated, and analyzed in ways that promote the synthesis of different studies. To this end, the BeeBiome consortium aims to develop an online database which would provide reference sequences, archive metadata, and host analytical resources. The goal would be to support applied and fundamental research on bees and their associated microbes and to provide a collaborative framework for sharing primary data from different research programs, thus furthering our understanding of the bee microbiome and its impact on pollinator health.
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