March 23, 2015

Publications by EEOB faculty March 1 - March 31

Development of neuropeptide analogs capable of traversing the integument: A case study using diapause hormone analogs in Helicoverpa zea

Qirui Zhang, Ronald J. Nachman, Krzysztof Kaczmarek, Krzysztof Kierus, Janusz Zabrocki, David L. Denlinger. 2015. Insect Biochemistry and Molecular Biology. doi:10.1016/j.ibmb.2015.02.015

Abstract

Diapause hormone and its analogs terminate pupal diapause in Helicoverpa zea when injected, but if such agents are to be used as effective diapause disruptors it will be essential to develop simple techniques for administering active compounds that can exert their effect by penetrating the insect epidermis. In the current study, we used two molecules previously shown to have high diapause-terminating activity as lead molecules to rationally design and synthesize new amphiphilic compounds with modified hydrophobic components. An assay for diapause termination identified 13 active compounds with EC₅₀'s ranging from 0.9 to 46.0 pmol per pupa. Three compounds, Decyl-1963, Dodecyl-1967, and Heptyl-1965, selected from the 13 compounds most active in breaking diapause following injection, also successfully prevented newly-formed pupae from entering diapause when applied topically. These compounds feature straight-chain, aliphatic hydrocarbons from 7 to 12 carbons in length; DH analogs with either a short-chain length of 4 or an aromatic phenethyl group failed to act topically. Compared to a high diapause incidence of 80–90% in controls, diapause incidence in pupae receiving a 10 nmole topical application of Decyl-1963, Dodecyl-1967, or Heptyl-1965 dropped to 30–45%. Decyl-1963 and Dodecyl-1967 also remained effective when topically applied at the 1 nmole level. These results suggest the feasibility of developing DH agonists that can be applied topically and suggest the identity of new lead molecules for development of additional topically-active DH analogs. The ability to penetrate the insect epidermis and/or midgut lining is critical if such agents are to be considered for future use as pest management tools.

The spread and persistence of influenza A viruses in waterfowl hosts in the North American Mississippi Migratory Flyway

Anthony C. Fries, Jacqueline M. Nolting, Andrew S. Bowman, Xudong Lin, Rebecca A. Halpin, Eric Wester, Nadia Fedorova, Timothy B. Stockwell, Suman Das, Vivien G. Dugan, David E. Wentworth, H. Lisle Gibbs, and Richard D. Slemons. 2015. Journal of Virology 89(8). doi: 10.1128/JVI.03249-14

Abstract

While geographic distance often restricts the spread of pathogens via hosts, this barrier may be compromised when host species are mobile. Migratory waterfowl in the Order Anseriformes are important reservoir hosts for diverse populations of avian-origin influenza A viruses (AIVs) and are assumed to spread AIVs during their annual continental-scale migrations. However, support for this hypothesis is limited and rarely tested using data from comprehensive surveillance efforts incorporating both the temporal and spatial aspects of host migratory patterns. Over three autumn migratory seasons we conducted intensive AIV surveillance in waterfowl using the North American Mississippi Migratory Flyway (MMF). Viral isolates (n=297) from multiple host species were sequenced and analyzed for patterns of gene dispersal between northern staging and southern wintering locations. Using a phylogenetic and nucleotide identity framework, we observed a greater amount of gene dispersal within rather than between the other three longitudinally identified North American flyways. Across seasons, we observed patterns of regional persistence of diversity for each genomic segment along with the limited survival of dispersed AIV gene lineages. Reassortment increased with both time and distance resulting in transient AIV constellations. This study shows that within the MMF,AIV gene flow favors spread along the migratory corridor within a season and that intensive surveillance during bird migration is important to identify virus dispersal on time scales relevant to pandemic responsiveness. In addition, this study indicates that comprehensive monitoring programs to capture AIV diversity are critical to provide insight into AIV evolution and ecology in a major natural reservoir.

Gibbs Lab

Identification of FOXO targets that generate diverse features of the diapause phenotype in the mosquito Culex pipiens

Cheolho Sim, David S. Kang, Sungshil Kim, Xiaodong Bai, and David L. Denlinger. 2015. PNAS. doi: 10.1073/pnas.1502751112

Abstract

Insulin and juvenile hormone signaling direct entry of the mosquito Culex pipiens into its overwintering adult diapause, and these two critical signaling pathways appear to do so by converging on the regulation of forkhead transcription factor (FOXO). Diapause is a complex phenotype, and FOXO emerges as a prime candidate for activating many of the diverse physiological pathways that generate the diapause phenotype. Here, we used ChIP sequencing to identify direct targets of FOXO. The nearest gene in a 10-kb region surrounding a predicted binding site was extracted for each binding site, resulting in a dataset containing genes potentially regulated by FOXO. By selecting candidate genes based on their functional relevance to diapause, we identified five gene categories of potential interest, including stress tolerance, metabolic pathways, lifespan extension, cell cycle and growth regulation, and circadian rhythms. Twelve targets were prioritized for further analysis, 10 of which were validated by ChIP-quantitative PCR and quantitative real-time PCR. These 10 genes activated by FOXO are highly up-regulated during diapause and are thus strong candidates for implementation of the diapause syndrome.

Lemuralges propithecus sp. n.(Acariformes: Psoroptidae), an ectoparasite of the diademed sifaka Propithecus diadema (Primates: Indriidae)

Andre V. Bochkov, Hans Klompen, Randall E. Junge and Cathy V. Williams. 2015. Folia Parasitologica 62:011 doi: 10.14411/fp.2015.011

Abstract

A new species of the genus Lemuralges Fain, 1963 (Acariformes: Psoroptidae: Makialginae) is described from the Mala-gasy lemur Propithecus diadema (Bennett) (Primates: Indriidae) based on all postembryonic instars. This new species differs from the only known species in this genus, Lemuralges intermedius Fain, 1963, by the following features: both sexes of L. propithecus sp. n. show a pair of medioventral projections of the subcapitulum (vs without projections in L. intermedius) and the propodonotal shield is slightly ornamented (vs unornamented); in males the hysteronotal shield is completely covered by longitudinal striae (vs median part without striae), setae c2 are 120–140 μm long (vs 200–210 μm long), and femur III has a short transverse furrow dorsally (vs a longitudinal furrow); in females, setae h2 are, at least, 2 times shorter than h3 (vs slightly longer, or subequal to, h3), tibia IV has a ventro-apical projection (vs without projection). Larvae and protonymphs of the new species show some unique developmental delays. Female and male tritonymphs differ by their external morphology.

Acarology lab

Net primary production of a temperate deciduous forest exhibits a threshold response to increasing disturbance severity

Ellen Stuart-Haëntjens, Peter S. Curtis, Robert T. Fahey, Christoph S. Vogel, and Christopher M. Gough. In press. Ecology. http://dx.doi.org/10.1890/14-1810.1

Abstract

The global carbon (C) balance is vulnerable to disturbances that alter terrestrial C storage. Disturbances to forests occur along a continuum of severity, from low intensity disturbance causing the mortality or defoliation of only a subset of trees to severe stand-replacing disturbance that kills all trees; yet, considerable uncertainty remains in how forest production changes across gradients of disturbance intensity. We used a gradient of tree mortality in an upper Great Lakes forest ecosystem to: 1) quantify how aboveground wood net primary production (ANPPw) responds to a range of disturbance severities and; 2) identify mechanisms supporting ANPPw resistance or resilience following moderate disturbance. We found that ANPPw declined non-linearly with rising disturbance severity, remaining stable until > 60 % of the total tree basal area senesced. As upper canopy openness increased from disturbance, greater light availability to the subcanopy enhanced the leaf-level photosynthesis and growth of this formerly light-limited canopy stratum, compensating for upper canopy production losses and a reduction in total leaf area index (LAI). As a result, whole-ecosystem production efficiency (ANPPw/LAI) increased with rising disturbance severity, except in plots beyond the disturbance threshold. These findings provide a mechanistic explanation for a non-linear relationship between ANPPw and disturbance severity, in which the physiological and growth enhancement of undisturbed vegetation is proportional to the level of disturbance until a threshold is exceeded. Our results have important ecological and management implications, demonstrating that in some ecosystems moderate levels of disturbance minimally alter forest production.

Curtis Lab