From The Hour I First Believed

Wally Lamb, a resident of Willimantic, Connecticut is the author of numerous best-selling novels including She\u27s Come Undone and I Know This Much Is True (both selections of the Oprah Book Club), and Couldn\u27t Keep It To Myself: Testimonies. The excerpt in this issue of OR is from his next novel, to appear from HarperCollins

Exploring Transferrin-Receptor Interactions at the Single-Molecule Level

Interaction between the iron transporter protein transferrin (Tf) and its receptor at the cell surface is fundamental for most living organisms. Tf receptor (TfR) binds iron-loaded Tf (holo-Tf) and transports it to endosomes, where acidic pH favors iron release. Iron-free Tf (apo-Tf) is then brought back to the cell surface and dissociates from TfR. Here we investigated the Tf-TfR interaction at the single-molecule level under different conditions encountered during the Tf cycle. An atomic force microscope tip functionalized with holo-Tf or apo-Tf was used to probe TfR. We tested both purified TfR anchored to a mica substrate and in situ TfR at the surface of living cells. Dynamic force measurements showed similar results for TfR on mica or at the cell surface but revealed striking differences between holo-Tf-TfR and apo-Tf-TfR interactions. First, the forces necessary to unbind holo-Tf and TfR are always stronger compared to the apo-Tf–TfR interaction. Second, dissociation of holo-Tf-TfR complex involves overcoming two energy barriers, whereas the apo-Tf-TfR unbinding pathway comprises only one energy barrier. These results agree with a model that proposes differences in the contact points between holo-Tf-TfR and apo-Tf-TfR interactions

Genetics and Genomics of Carrot Biotic Stress

International audienceCarrot (Daucus carota ssp. sativus) production can be affected by a wide range of pests and pathogens. At least five diseases of carrot are caused by bacterial pathogens, 36 by fungal and oomycete pathogens, two by phytoplasmas, and 13 by viruses; and seven genera of nematodes and two genera of parasitic plants affect carrot. In addition, numerous insect and mite pests can cause losses. There have been extensive efforts to select carrot cultivars with partial or complete resistance to many of these pathogens and pests, and to identify wild species with resistance to specific biotic stresses for introgression into breeding populations and commercial cultivars. For some pathogens and pests, significant advances have been made at identifying resistance and mapping that resistance to the carrot genome. For others, resistance has been identified, but the genetic basis is yet to be determined. For a majority of these diverse stresses, however, there has been little success at identifying highly effective resistance and understanding the genetic basis of resistance. The diversity of stresses as well as interactions among these pests and pathogens can complicate efforts to develop cultivars with resistance to all key biotic stresses in a region that also meet market and consumer expectations. New approaches to identifying resistant material and speeding traditional breeding are being developed with molecular breeding tools, including simple sequence repeat markers and deep-coverage libraries of the carrot genome. These valuable genomic resources will enhance efforts to identify and breed for resistance to carrot pests and pathogens