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Kubanek, Julia

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Now showing 1 - 4 of 4
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    Genetic determinants of mate recognition in Brachionus manjavacas (Rotifera)
    (Georgia Institute of Technology, 2009-09-09) Snell, Terry W. ; Shearer, Tonya L ; Smith, Hilary A. ; Kubanek, Julia ; Gribble, Kristin E. ; Welch , David B. Mark
    Background: Mate choice is of central importance to most animals, influencing population structure, speciation, and ultimately the survival of a species. Mating behavior of male brachionid rotifers is triggered by the product of a chemosensory gene, a glycoprotein on the body surface of females called the mate recognition pheromone. The mate recognition pheromone has been biochemically characterized, but little was known about the gene(s). We describe the isolation and characterization of the mate recognition pheromone gene through protein purification, N-terminal amino acid sequence determination, identification of the mate recognition pheromone gene from a cDNA library, sequencing, and RNAi knockdown to confirm the functional role of the mate recognition pheromone gene in rotifer mating. Results: A 29 kD protein capable of eliciting rotifer male circling was isolated by high-performance liquid chromatography. Two transcript types containing the N-terminal sequence were identified in a cDNA library; further characterization by screening a genomic library and by polymerase chain reaction revealed two genes belonging to each type. Each gene begins with a signal peptide region followed by nearly perfect repeats of an 87 to 92 codon motif with no codons between repeats and the final motif prematurely terminated by the stop codon. The two Type A genes contain four and seven repeats and the two Type B genes contain three and five repeats, respectively. Only the Type B gene with three repeats encodes a peptide with a molecular weight of 29 kD. Each repeat of the Type B gene products contains three asparagines as potential sites for N-glycosylation; there are no asparagines in the Type A genes. RNAi with Type A double-stranded RNA did not result in less circling than in the phosphate-buffered saline control, but transfection with Type B double-stranded RNA significantly reduced male circling by 17%. The very low divergence between repeat units, even at synonymous positions, suggests that the repeats are kept nearly identical through a process of concerted evolution. Information-rich molecules like surface glycoproteins are well adapted for chemical communication and aquatic animals may have evolved signaling systems based on these compounds, whereas insects use cuticular hydrocarbons. Conclusion: Owing to its critical role in mating, the mate recognition pheromone gene will be a useful molecular marker for exploring the mechanisms and rates of selection and the evolution of reproductive isolation and speciation using rotifers as a model system. The phylogenetic variation in the mate recognition pheromone gene can now be studied in conjunction with the large amount of ecological and population genetic data being gathered for the Brachionus plicatilis species complex to understand better the evolutionary drivers of cryptic speciation.
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    Chemically mediated competition between microbes and animals: microbes as consumers in food webs
    (Georgia Institute of Technology, 2006-11) Burkepile, Deron E. ; Parker, John D. ; Woodson, Clifton Brock ; Mills, Heath Jordan ; Kubanek, Julia ; Sobecky, Patricia A. ; Hay, Mark E.
    Microbes are known to affect ecosystems and communities as decomposers, pathogens, and mutualists. However, they also may function as classic consumers and competitors with animals if they chemically deter larger consumers from using rich food-falls such as carrion, fruits, and seeds that can represent critical windfalls to both microbes and animals. Microbes often use chemicals (i.e., antibiotics) to compete against other microbes. Thus using chemicals against larger competitors might be expected and could redirect significant energy subsidies from upper trophic levels to the detrital pathway. When we baited traps in a coastal marine ecosystem with fresh vs. microbe-laden fish carrion, fresh carrion attracted 2.6 times as many animals per trap as microbe-laden carrion. This resulted from fresh carrion being found more frequently and from attracting more animals when found. Microbe-laden carrion was four times more likely to be uncolonized by large consumers than was fresh carrion. In the lab, the most common animal found in our traps (the stone crab Menippe mercenaria) ate fresh carrion 2.4 times more frequently than microbe-laden carrion. Bacteria-removal experiments and feeding bioassays using organic extracts of microbe-laden carrion showed that bacteria produced noxious chemicals that deterred animal consumers. Thus bacteria compete with large animal scavengers by rendering carcasses chemically repugnant. Because food-fall resources such as carrion are major food subsidies in many ecosystems, chemically mediated competition between microbes and animals could be an important, common, but underappreciated interaction within many communities.
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    Drugs from the Sea
    (Georgia Institute of Technology, 2006-08-26) Ludovice, Peter J. ; Hunt, William D. ; Kubanek, Julia
    Our guest Prof. Julia Kubanek from the School of Biology and the School of Chemistry and Biochemistry at Georgia Tech will discuss how pharmaceutical agents can be extracted from marine organisims.
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    Chemical Cues in the Ocean
    (Georgia Institute of Technology, 2006-04-25) Kubanek, Julia
    We are all at the mercy of molecules: hormones affect our sexual interests, toxins give us food poisoning, polluting chemicals give us asthma, and the smell of Krispy Kreme tugs on the steering wheel whenever we drive along Ponce de Leon Ave. Molecules play an even greater role in the lives of marine plants, animals, and microorganisms. On coral reefs and in the open ocean, chemicals affect who eats who, who settles down next to who, and who can fight off a potentially deadly infection. In lab and field experiments, Georgia Tech faculty and students are working to understand the role of natural chemical compounds in the survival and reproduction of marine organisms.