SignificanceNutritional symbionts in sap-feeding insects are characterized by highly degenerate genomes. It is poorly understood how hosts evolve to maintain these symbionts, particularly when hosts rely on more than one symbiont that requires distinct support for basic cell functions. We show that the aster leafhopper (Macrosteles quadrilineatus), which depends on two symbionts with tiny genomes (Sulcia and Nasuia), has differentially reprogramed gene-expression patterns in symbiont-associated cells. The host has acquired novel genetic traits and likely recruited preexisting mitochondrial support mechanisms to meet the specific needs of each symbiont. Broad comparisons across anciently diverged sap-feeding hosts reveal that the evolution of symbiont support mechanisms is largely unique to each host lineage. Important parallels are further observed with organelle evolution.

We previously determined that several diets used to rear Aedes aegypti and other mosquito species support the development of larvae with a gut microbiota but do not support the development of axenic larvae. In contrast, axenic larvae have been shown to develop when fed other diets. To understand the mechanisms underlying this dichotomy, we developed a defined diet that could be manipulated in concert with microbiota composition and environmental conditions. Initial studies showed that axenic larvae could not grow under standard rearing conditions (27 °C, 16-h light: 8-h dark photoperiod) when fed a defined diet but could develop when maintained in darkness. Downstream assays identified riboflavin decay to lumichrome as the key factor that prevented axenic larvae from growing under standard conditions, while gut community members like Escherichia coli rescued development by being able to synthesize riboflavin. Earlier results showed that conventional and gnotobiotic but not axenic larvae exhibit midgut hypoxia under standard rearing conditions, which correlated with activation of several pathways with essential growth functions. In this study, axenic larvae in darkness also exhibited midgut hypoxia and activation of growth signaling but rapidly shifted to midgut normoxia and arrested growth in light, which indicated that gut hypoxia was not due to aerobic respiration by the gut microbiota but did depend on riboflavin that only resident microbes could provide under standard conditions. Overall, our results identify riboflavin provisioning as an essential function for the gut microbiota under most conditions A. aegypti larvae experience in the laboratory and field.

Three-dimensional (3D) electrodes are critical for enabling high-performance power sources. We report here on the design and fabrication, by combining imprint and soft-printing technologies, of 3D nanocone arrays as a novel platform for high performance pseudocapacitors. Such purpose-built 3D nanocone arrays have the advantages of simplicity/versatility/reliability of fabrication, generality to a vast range of active materials, high electrode surface area, and ease of electrolyte permeation. As a demonstration of principle, Au and MnO2 were sequentially deposited forming a 3D Au/MnOx nanocone array electrode for a pseudocapacitor device. This device achieved a specific mass (areal) capacitance of 840.3 F g(-1) (88.2 mF cm(-2)) at a current density of 2 A g(-1). Additionally, the asymmetric supercapacitor using the Au/MnOx nanocone array as the positive electrode and a carbon-based material as the negative electrode achieved a capacitance of 108.5 F g(-1) at a current density of 1 A g(-1), corresponding to an energy density of as high as 46.8 W h kg(-1) at a power density of 0.72 kW kg(-1). The cell still preserved 96.5% of the initial capacitance even after 2000 cycles at a current density of 2 A g(-1). The initial result is at least on a par with those of the best asymmetric supercapacitors reported so far, and thus bolsters the development value of the conductive nanocone arrays for high-performance supercapacitors and other energy-storage devices.

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Insect species in the Auchenorrhyncha suborder (Hemiptera) maintain ancient obligate symbioses with bacteria that provide essential amino acids (EAAs) deficient in their plant-sap diets. Molecular studies have revealed that two complementary symbiont lineages, “Candidatus Sulcia muelleri” and a betaproteobacterium (“Ca. Zinderia insecticola” in spittlebugs [Cercopoidea] and “Ca. Nasuia deltocephalinicola” in leafhoppers [Cicadellidae]) may have persisted in the suborder since its origin ∼300 Ma. However, investigation of how this pair has co-evolved on a genomic level is limited to only a few host lineages. We sequenced the complete genomes of Sulcia and a betaproteobacterium from the treehopper, Entylia carinata (Membracidae: ENCA), as the first representative from this species-rich group. It also offers the opportunity to compare symbiont evolution across a major insect group, the Membracoidea (leafhoppers + treehoppers). Genomic analyses show that the betaproteobacteria in ENCA is a member of the Nasuia lineage. Both symbionts have larger genomes (Sulcia = 218 kb and Nasuia = 144 kb) than related lineages in Deltocephalinae leafhoppers, retaining genes involved in basic cellular functions and information processing. Nasuia-ENCA further exhibits few unique gene losses, suggesting that its parent lineage in the common ancestor to the Membracoidea was already highly reduced. Sulcia-ENCA has lost the abilities to synthesize menaquinone cofactor and to complete the synthesis of the branched-chain EAAs. Both capabilities are conserved in other Sulcia lineages sequenced from across the Auchenorrhyncha. Finally, metagenomic sequencing recovered the partial genome of an Arsenophonus symbiont, although it infects only 20% of individuals indicating a facultative role.

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Aim East Asia is known for its exceptionally high levels of biodiversity, which is connected to its high level of species differentiation. Geological movements are the most important factor promoting the species differentiation in East Asia. In this paper, we choose Biston panterinaria, a moth species widely distributed in East Asia, to study the relative contributions of geographical isolation and glaciation cycles to its current genetic constitution. Location East Asia.Methods Phylogenetic analyses were based on three data sets. beast was used to estimate the divergence time and reconstruct the maximum clade credibility tree. Mismatch distribution and Bayesian skyline plots (BSP) were used to infer historical population fluctuations. maxent was used to predict the potential species distributions during two periods: the present day and the Last Glacial Maximum (LGM).Results The phylogenetic tree and the median joining network strongly supported four reciprocally monophyletic lineages: northern, Yunnan-Tibet, southern and Yunnan-SE. The estimates of divergence time suggested that three differentiation processes occurred at approximately 1.17, 0.76 and 0.67 Ma. Within the northern and southern lineages, lineage divergence occurred at approximately 0.17 and 0.16 Ma. Mismatch distribution and BSP suggested that the northern and southern lineages experienced one expansion after the LGM, and this result was consistent with the result of the ecological niche model. Main conclusionsOur results suggested that B. panterinaria experienced three fragmentations of wide-ranging ancestral populations, and that mountain barrier isolation induced by geological movements is the main driver of lineage differentiation. Climatic oscillations during the Pleistocene affected the population differentiation within both the northern and southern lineages. The distribution of the four lineages of B. panterinaria is generally consistent with the zoogeographical regionalization of China. This study provides direct evidence for the importance of mountain barriers in promoting population differentiation.