Publications by EEOB faculty in Dec 2013-Jan 2014

January 30, 2014

Molecular identification and expression analysis of a diapause hormone receptor in the corn earworm, Helicoverpa zea.

Q Zhang, PM Piermarini, RJ Nachman and DL Denlinger. 2013. Peptides, in press. DOI: 10.1016/j.peptides.2013.12.005

Abstract Diapause hormone (DH) is an insect neuropeptide that is highly effective in terminating the overwintering pupal diapause in members of the Helicoverpa/Heliothis complex of agricultural pests, thus DH and related compounds have promise as tools for pest management. To augment our development of effective DH analogs and antagonists that could be used as diapause disruptors this study focuses on the cloning and identification of the DH receptor (DHR) in the corn earworm, Helicoverpa zea. The full-length dhr cDNA contains 2153 nucleotides encoding 511 amino acids. Our results suggest there are at least two splicing variants of Hezea-DHR. Hydrophobicity analysis and sequence alignment indicate that Hezea- DHR has 7 transmembrane regions and a highly conserved C-terminal region that is also present in related receptors. Hezea-DHR has 95%, 82% and 79% identity to a partial DHR sequence from Heliothis virescens, a full-length DHR in Orgyia thyellina, and DHR-1 in Bombyx mori, but only 45-49% identity to pheromone biosynthesis activating neuropeptide receptor (PBANR). Expression of dhr mRNA remained low in whole body extracts throughout diapause and in young nondiapausing pupae, but was distinctly elevated as development ensued in pharate adults 7 days after pupation. The highest expression of dhr mRNA we noted was in the ovary. A DHR fusion protein with enhanced-green fluorescent protein was successfully expressed heterologously in X. laevis oocytes, as verified by fluorescent imaging and Western blots, but an electrophysiological assay failed to detect receptor-ligand binding activity, which suggests that an essential cofactor and/or accessory protein is required for functional activity of the DHR.

Denlinger lab

Surviving in a frozen desert: environmental stress physiology of terrestrial Antarctic arthropods.

NM Teets and DL Denlinger. 2014. The Journal of Experimental Biology, in press. DOI: 10.1242/jeb.089490

Abstract Abiotic stress is one of the primary constraints limiting the range and success of arthropods, and nowhere is this more apparent than Antarctica. Antarctic arthropods have evolved a suite of adaptations to cope with extremes in temperature and water availability. Here, we review the current state of knowledge regarding the environmental physiology of terrestrial arthropods in Antarctica. To survive low temperatures, mites and Collembola are freeze-intolerant and rely on deep supercooling, in some cases supercooling below -30°C. Also, some of these microarthropods are capable of cryoprotective dehydration to extend their supercooling capacity and reduce the risk of freezing. In contrast, the two best-studied Antarctic insects, the midges Belgica antarctica and Eretmoptera murphyi, are freeze-tolerant year-round and rely on both seasonal and rapid cold-hardening to cope with decreases in temperature. A common theme among Antarctic arthropods is extreme tolerance of dehydration; some accomplish this by cuticular mechanisms to minimize water loss across their cuticle, while a majority have highly permeable cuticles but tolerate upwards of 50--70% loss of body water. Molecular studies of Antarctic arthropod stress physiology are still in their infancy, but several recent studies are beginning to shed light on the underlying mechanisms that govern extreme stress tolerance. Some common themes that are emerging include the importance of cuticular and cytoskeletal rearrangements, heat shock proteins, metabolic restructuring and cell recycling pathways as key mediators of cold and water stress in the Antarctic.

Denlinger lab

Use of "Bioavailability" as a term in ecotoxicology.

MJ McLaughlin and R Lanno. 2014. Integr. Environ. Assess. Manag., 10, 138--140. DOI: 10.1002/ieam.1497

Abstract Two terms commonly used in both aquatic and terrestrial ecotoxicology are ''bioavailability'' and ''bioaccessibility'', and the interchangeable use of these two distinctive concepts in the scientific literature causes great confusion (Semple et al. 2004). Here we remind readers of the differences between these concepts and their distinction from ''extractability'' so that the inappropriate use of these terms can be avoided.

Lanno Lab

Mobile pastoralists in the Logone Floodplain distribute themselves in an Ideal Free Distribution.

Mark Moritz, Ian M Hamilton, Yu-Jen Chen and Paul Scholte. 2014. Current Anthropology 55, in press. DOI: 10.1086/674717

Abstract We examined whether mobile pastoralists in the Logone floodplain of Cameroon distribute themselves according to the ideal free distribution (IFD), which predicts that the number of individuals in each area is proportional to the quality and quantity of resources in each area and that all individuals have access to the same amount of resources. We used the concept to assess the distribution of grazing pressure over available common-pool resources as evidence of a complex adaptive system in which the spatial distribution grazing pressure is adjusted to the distribution of resources through individual decision making and passive coordination of movements among individual pastoralists. We used a combination of spatial and ethnographic approaches to study the distribution of resources and mobile pastoralists in the Logone floodplain in 5 successive years and found evidence for an IFD in 3 years (2008–2009 and 2012) and an approximation of an IFD in years in which pastoralists were terrorized by armed bandits (2010) and the government reestablished security (2011). The findings support our hypothesis that there is a self-organizing management system in which pastoralists distribute themselves effectively over the available resources.

Hamilton Lab

Learning to Detect Basal Tubules of Nematocysts in SEM images.

Michael Lam, Janardhan Rao Doppa, Xu Hu, Sinisa Todorovic, Thomas Dietterich, Abigail Reft, and Marymegan Daly. 2014. PDF

Abstract This paper presents a learning approach for detecting nematocysts in Scanning Electron Microscope (SEM) images. The image dataset was collected and made available to us by biologists for the purposes of morphological studies of corals, jellyfish, and other species in the phylum Cnidaria. Challenges for computer vision presented by this biological domain are rarely seen in general images of natural scenes. We formulate nematocyst detection as labeling of a regular grid of image patches. This structured prediction problem is specified within two frameworks: CRF and HC-Search. The CRF uses graph cuts for inference. The HC-Search approach is based on search in the space of outputs. It uses a learned heuristic function (H) to uncover high-quality candidate labelings of image patches, and then uses a learned cost function (C) to select the final prediction among the candidates. While locally optimal CRF inference may be sufficient for images of natural scenes, our results demonstrate that CRF with graph cuts performs poorly on the nematocyst images, and that HC-Search outperforms CRF with graph cuts. This suggests biological images of flexible objects present new challenges requiring further advances of, or alternatives to existing methods.

Daly Lab