Editors' Choice

Science  19 Jan 2007:
Vol. 315, Issue 5810, pp. 302

    Generating Varieties

    1. Laura M. Zahn

    Paralogs are the result of a gene duplication event arising after speciation. By examining expressed sequence tags (ESTs) in the B73 strain of maize, Emrich et al. identified gene copies with 98% or more similarity, which they have labeled as nearly identical paralogs (NIPs). Approximately 1% of all genes in maize (Zea mays L.) have a NIP, a significantly higher rate than found in Arabidopsis. Many of these NIPs demonstrate linkage, suggesting that they originated via tandem gene duplication. Among NIP families it was found that both gene copies were often expressed (∼80%) and that the expression of an individual gene often differed from that of its paralog. These data suggest that paralogs may be a means by which organisms generate variation and, in the case of maize, may have been important in providing varieties for selection and domestication by humans. — LMZ

    Genetics 10.1534/genetics.106.064006 (2006).


    Morality on the Web

    1. Gilbert J. Chin

    Inconsistencies—for instance, between what is observed and what is reported—can be fecund ground for researchers to till, and a topic of current interest is the incongruence between the moral judgments that people make and the reasons that people proffer as a basis for those judgments. At one side are the proponents of conscious or deliberative thought as the means for making choices when confronted with moral dilemmas, whereas another view favors intuitions arrived at via automatic or inaccessible processes as the motivation for their responses.

    Cushman et al. have elicited “ought versus ought not” judgments and postjudgment rationales from more than 500 people by using a Web-based script. Participants read carefully constructed scenarios and registered their judgments; they were then presented with their choices in pairs of the scenarios that differed in only one of three dimensions and asked for a justification. In situations where action (or inaction) was involved, participants were consistent in their judgments and generally had no difficulty in articulating a reasoned argument for how they had decided which behavior was morally better. In contrast, when intentional (or unintentional) harm was the issue, the pattern of judgment was just as clear as in the action scenarios, but most participants could not explain why they had chosen as they did. Hence, there may be more than one way to reach a decision on morality. — GJC

    Psychol. Sci. 17, 1082 (2006).


    From Soup to Nuts

    1. Marc S. Lavine

    The promise of microfluidic systems, in which very small volumes of liquids are manipulated, processed, and interrogated, is that it may be possible to develop low-cost diagnostic systems, particularly for use under challenging field conditions. Although there has been tremendous progress in developing microfluidic components, creating an integrated system that can analyze an unpurified sample has remained a goal.

    Easley et al. describe a microfluidic system with three distinct functional domains. The first two are for sample preparation, consisting of solid-phase extraction (SPE) to pull out sample DNA from a crude specimen and for subsequent PCR amplification. After this, the amplified products are then injected along with a DNA standard into an electrophoretic detection domain. One key aspect of the device (3 × 6 cm) is a series of valves that are used to isolate each unit, thus keeping SPE reagents from reaching the PCR domain; these valves are also used in a diaphragm-like fashion to pump the amplified DNA into the analytical chamber. The authors demonstrate the detection of Bacillus anthracis in 750 nl of whole blood taken from infected but asymptomatic mice, and they also are able to measure Bordetella pertussis in 1 μl of nasal aspirate taken from a patient suspected of having whooping cough. — MSL

    Proc. Natl. Acad. Sci. U.S.A. 103, 19272 (2006).


    A Loss of Intestinal Fortitude

    1. Stephen J. Simpson

    The large-scale and rapid depletion of CD4+ T cells in the weeks after HIV infection occurs predominantly in the gastrointestinal tract. Accompanying this loss is a sustained whole-scale activation of the immune system, which corresponds directly with the eventual progression to AIDS.

    Brenchley et al. propose that the two processes are tightly coupled, with impaired intestinal integrity leading to the translocation of gut microbes, or some of their constituent components, which overstimulate the immune system. Circulating levels of bacterial lipopolysaccharide (LPS), which was used as a marker for microbial translocation, were markedly elevated in the sera of chronically infected HIV individuals and in macaques experimentally infected with the simian immunodeficiency virus (SIV). This increase corresponded directly with footprints of immune activation, including circulating cytokines, antibodies to LPS, and immune-cell turnover. In HIV patients undergoing highly active antiretroviral therapy, LPS levels were decreased, with a corresponding rebound in CD4+ T cell numbers. Furthermore, in the absence of pathology—as typified in the infection of natural primate hosts for SIV—signs of substantial microbial translocation or immune activation were not apparent. The link between HIV infection, integrity of the mucosal immune system, and chronic peripheral immune activation may prove important to consider in future therapies for HIV infection. — SJS

    Nat. Med. 12, 1365 (2006).


    Eavesdropping Foiled by Decoys

    1. Ian S. Osborne

    Secure communication between a sender and a receiver generally requires the message to be encrypted, with the sender and recipient sharing a secret key that encodes and deciphers the message. Ideally, the key should be changed often, and so for practical reasons the key should be distributable over normal communication channels. However, the possibility of the interception of the key by an eavesdropper would compromise security. There is, therefore, a need for a method to distribute the key to the recipient securely so that any attack on the communication channel by a potential eavesdropper can be detected and appropriate action taken.

    Yuan et al. use a combination of signal and decoy optical pulses sent over a 25-km optic fiber to demonstrate unconditionally secure quantum-key distribution to a recipient. Because the decoy pulses are weaker than the signal pulses, interception by an eavesdropper considerably reduces their transmission rate to the receiver, thereby revealing the existence of an eavesdropper. Although the use of decoy pulses does provide for secure communication, it also places stringent requirements on the calibration of the sources and the detectors so that artifacts do not compromise security. — ISO

    Appl. Phys. Lett. 90, 011118 (2007).


    Stabilizing Porphyrin Stacks

    1. Phil D. Szuromi

    Expanded porphyrins are larger versions of the familiar tetrapyrrole compounds. These extended aromatic frameworks could potentially form discotic, liquid-crystalline phases, but the floppiness of the electron-rich structure disrupts stacking.

    StGraphicpieñ et al. have prepared cyclo[8]pyrrole cations bearing phenylalkyl side chains and a central sulfate counter-ion. They find that electron- acceptor molecules such as trinitrobenzene (TNB) form 1:1 adducts with the expanded porphyrins, which leads to changes in color and can produce columnar stacking and the formation of discotic mesophases. This approach, if successfully applied to related explosives such as TNT (trinitrotoluene), might provide a simple visual method for detection or sensing. — PDS

    Angew. Chem. Int. Ed. 10.1002/anie.200603893 (2006).

  7. STKE

    A Balance Between Life and Death

    1. L. Bryan Ray

    Cancerous cells often exhibit not only a capacity for excessive proliferation but also a resistance to apoptosis. For example, the oncoprotein c-MYC, an important contributor to many human tumors, activates the transcription of some genes and represses that of others and thus influences many target genes that might contribute to the regulation of apoptosis. Patel and McMahon have extended earlier studies that showed that the binding of c-Myc to the transcription factor MIZ-1 and the inhibition of MIZ-1-dependent transcription were important for promoting apoptosis. In human fibroblasts, a form of c-MYC (c-MYCV394D) that does not interact with MIZ-1 was defective in inducing apoptosis. Furthermore, when the level of MIZ-1 was reduced in these cells, the apoptotic effect of c-MYCV394D was restored. MIZ-1 activates the transcription of several hundred genes, and a search of target genes in microarrays yielded a promising candidate: the gene encoding the antiapoptotic protein BCL2. Indeed, expression of BCL2 was decreased by c-MYC but not by c-MYCV394D, and inhibiting BCL2 expression rescued the ability of c-MYCV394D to promote apoptosis. Previous studies of mouse models and of human tumor cells have shown that BCL2 and c-MYC appear to work together in promoting cancer, and these results indicate that transcription of the BCL2 gene is regulated through c-MYC and MIZ-1. — LBR

    J. Biol. Chem. 282, 5 (2007).

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