More Like this

1. microRNA regulation in an ancient obligate endosymbiosis

   https://doi.org/10.1111/mec.14464  

   Feng, Honglin ; Wang, Lingyu ; Wuchty, Stefan ; Wilson, Alex C. C. ( January 2018 , Molecular Ecology)

   Although many insects are associated with obligate bacterial endosymbionts, the mechanisms by which these host/endosymbiont associations are regulated remain mysterious. While microRNAs (miRNAs) have been recently identified as regulators of host/microbe interactions, including host/pathogen and host/facultative endosymbiont interactions, the role miRNAs may play in mediating host/obligate endosymbiont interactions is virtually unknown. Here, we identified conserved miRNAs that potentially mediate symbiotic interactions between aphids and their obligate endosymbiont,Buchnera aphidicola. Using smallRNAsequence data fromMyzus persicaeandAcyrthosiphon pisum, we annotated 93M. persicaeand 89A. pisummiRNAs, among which 69 were shared. We found 14 miRNAs that were either highly expressed in aphid bacteriome, theBuchnera‐housing tissue, or differentially expressed in bacteriome vs. gut, a non‐Buchnera‐housing tissue. Strikingly, 10 of these 14 miRNAs have been implicated previously in other host/microbe interaction studies. Investigating the interaction networks of these miRNAs using a custom computational pipeline, we identified 103 miRNA::mRNAinteractions shared betweenM. persicaeandA. pisum. Functional annotation of the sharedmRNAtargets revealed only two over‐represented cluster of orthologous group categories: amino acid transport and metabolism, and signal transduction mechanisms. Our work supports a role for miRNAs in mediating host/symbiont interactions between aphids and their obligate endosymbiontBuchnera. In addition, our results highlight the probable importance of signal transduction mechanisms to host/endosymbiont coevolution.

    

   more » « less
2. Dehydroepiandrosterone Heightens Aggression and Increases Androgen Receptor and Aromatase mRNA Expression in the Brain of a Male Songbird

   https://doi.org/10.1111/jne.12443  

   Wacker, D. W. ; Khalaj, S. ; Jones, L. J. ; Champion, T. L. ; Davis, J. E. ; Meddle, S. L. ; Wingfield, J. C. ( December 2016 , Journal of Neuroendocrinology)

   Dehydroepiandrosterone (DHEA) is a testosterone/oestrogen precursor and known modulator of vertebrate aggression. Male song sparrows (Melospiza melodia morphna) show high aggression during breeding and nonbreeding life‐history stages when circulatingDHEAlevels are high, and low aggression during molt whenDHEAlevels are low. We previously showed that androgen receptor and aromatasemRNAexpression are higher during breeding and/or nonbreeding in brain regions associated with reproductive and aggressive behaviour, although the potential role ofDHEAin mediating these seasonal changes remained unclear. In the present study, nonbreeding male song sparrows were captured and held in the laboratory under short days (8 : 16 h light/dark cycle) and implanted with s.c.DHEA‐filled or empty (control) implants for 14 days.DHEAimplants increased aggression in a laboratory‐based simulated territorial intrusion. Brains ofDHEA‐implanted birds showed higher aromatasemRNAexpression in the preoptic area (POA) and higher androgen receptormRNAexpression in the periventricular nucleus of the medial striatum (pvMSt) and ventromedial nucleus of the hypothalamus. TheDHEA‐induced increases in aromatase expression in thePOAand androgen receptor expression in the pvMSt are consistent with previously reported seasonal increases in these markers associated with naturally elevatedDHEAlevels. This suggests thatDHEAfacilitates seasonal increases in aggression in nonbreeding male song sparrows by up‐regulating steroid signalling/synthesis machinery in a brain region‐specific fashion.

    

   more » « less
3. Population genomics of divergence among extreme and intermediate color forms in a polymorphic insect

   https://doi.org/10.1002/ece3.1928  

   Lozier, Jeffrey D. ; Jackson, Jason M. ; Dillon, Michael E. ; Strange, James P. ( January 2016 , Ecology and Evolution)

   Geographic variation in insect coloration is among the most intriguing examples of rapid phenotypic evolution and provides opportunities to study mechanisms of phenotypic change and diversification in closely related lineages. The bumble beeBombus bifariuscomprises two geographically disparate color groups characterized by red‐banded and black‐banded abdominal pigmentation, but with a range of spatially and phenotypically intermediate populations across western North America. Microsatellite analyses have revealed thatB. bifariusin the USA are structured into two major groups concordant with geography and color pattern, but also suggest ongoing gene flow among regional populations. In this study, we better resolve the relationships among major color groups to better understand evolutionary mechanisms promoting and maintaining such polymorphism. We analyze >90,000 and >25,000 single‐nucleotide polymorphisms derived from transcriptome (RNAseq) and double digest restriction site associatedDNAsequencing (ddRAD), respectively, in representative samples from spatial and color pattern extremes inB. bifariusas well as phenotypic and geographic intermediates. Both ddRADandRNAseq data illustrate substantial genome‐wide differentiation of the red‐banded (eastern) color form from both black‐banded (western) and intermediate (central) phenotypes and negligible differentiation among the latter populations, with no obvious admixture among bees from the two major lineages. Results thus indicate much stronger background differentiation amongB. bifariuslineages than expected, highlighting potential challenges for revealing loci underlying color polymorphism from population genetic data alone. These findings will have significance for resolving taxonomic confusion in this species and in future efforts to investigate color‐pattern evolution inB. bifariusand other polymorphic bumble bee species.

    

   more » « less
4. The Magnitude of Regional‐Scale Tree Mortality Caused by the Invasive Pathogen Phytophthora ramorum

   https://doi.org/10.1029/2020EF001500  

   Cobb, Richard C. ; Haas, Sarah E. ; Kruskamp, Nicholas ; Dillon, Whalen W. ; Swiecki, Tedmund J. ; Rizzo, David M. ; Frankel, Susan J. ; Meentemeyer, Ross K. ( July 2020 , Earth's Future)

   Forest pathogens are important drivers of tree mortality across the globe, but it is exceptionally challenging to gather and build unbiased quantitative models of their impacts. Here we harness the rare data set matching the spatial scale of pathogen invasion, host, and disease heterogeneity to estimate infection and mortality for the four most susceptible host species ofPhytophthora ramorum, an invasive pathogen that drives the most important biological cause of tree mortality in a broad geographic region of coastal California and southwest Oregon. As of 2012, the most current field survey year, we estimate 17.5 (±4.6, 95% CI [confidence interval]) million tanoak (Notholithocarpus densiflorus) stems were pathogen killed with an additional 71 (±21.5) million infected. We estimated 9.0 million (±2.2) coast live oak (Quercus agrifolia) and 1.7 million (±0.5) California black oak (Quercus kelloggii) stems are disease impacted (mortality and infection combined). Lastly, our estimates suggest infection in 95.2 million (±8.6) California bay laurel (Umbellularia californica), which does not suffer mortality from infection and represents a critical source of continued spread. Prevalent infection as of 2012 suggests the cumulative number of disease‐killed stems likely increased from 20.8 to 42.8 million between 2012 and 2019 for all species. While these impacts are substantial, most host populations occur in a yet to be invaded region of northern California indicating that the disease will intensify in the coming decades.

    

   more » « less
5. TaADF4 , an actin‐depolymerizing factor from wheat, is required for resistance to the stripe rust pathogen Puccinia striiformis f. sp. tritici

   https://doi.org/10.1111/tpj.13459  

   Zhang, Bing ; Hua, Yuan ; Wang, Juan ; Huo, Yan ; Shimono, Masaki ; Day, Brad ; Ma, Qing ( February 2017 , The Plant Journal)

   Actin filament assembly in plants is a dynamic process, requiring the activity of more than 75 actin‐binding proteins. Central to the regulation of filament assembly and stability is the activity of a conserved family of actin‐depolymerizing factors (ADFs), whose primarily function is to regulate the severing and depolymerization of actin filaments. In recent years, the activity ofADFproteins has been linked to a variety of cellular processes, including those associated with response to stress. Herein, a wheatADFgene,TaADF4,was identified and characterized.TaADF4encodes a 139‐amino‐acid protein containing five F‐actin‐binding sites and two G‐actin‐binding sites, and interacts with wheat (Triticum aestivum) Actin1 (TaACT1),in planta. Following treatment of wheat, separately, with jasmonic acid, abscisic acid or with the avirulent race,CYR23, of the stripe rust pathogenPuccinia striiformisf. sp.tritici, we observed a rapid induction in accumulation ofTaADF4mRNA. Interestingly, accumulation ofTaADF4mRNAwas diminished in response to inoculation with a virulent race,CYR31. Silencing ofTaADF4resulted in enhanced susceptibility toCYR23, demonstrating a role forTaADF4in defense signaling. Using a pharmacological‐based approach, coupled with an analysis of host response to pathogen infection, we observed that treatment of plants with the actin‐modifying agent latrunculin B enhanced resistance toCYR23, including increased production of reactive oxygen species and enhancement of localized hypersensitive cell death. Taken together, these data support the hypothesis thatTaADF4 positively modulates plant immunity in wheat via the modulation of actin cytoskeletal organization.

    

   more » « less