Science  09 Dec 2011:
Vol. 334, Issue 6061, pp. 1329

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  1. Voltage Change Forms Eyes In Head—Or Wherever

    Electric eye.

    A little voltage produces peepers.


    A natural bioelectrical current jumpstarts normal eye development in frogs, researchers have discovered—suggesting a new route toward repairing damaged or diseased eyes.

    Almost all cell membranes have “ion channels” that let charged particles move in and out—the essence of an electrical current. But the first clue that bioelectricity might be critical to eyes came a decade ago when Michael Levin at Tufts University in Medford, Massachusetts, and his colleagues altered the number of ion channels in cells in different parts of a frog embryo and found that lens and retinal tissue formed outside the head. Later work by others showed that cells destined to become eyes had an excessive negative charge.

    Levin's team has now verified that these pre-eye cells were hyperpolarized, produced DNA regulatory proteins important for eye formation, and did become a lens and retina. Modifying the function of ion channels in four-cell frog embryos led to eyes in the tail and on the gut, but only where cells experienced a particular voltage range, the researchers reported this week in Development. “Bioelectrical information is both necessary and sufficient for inducing development of the vertebrate eye,” comments James Coffman, a developmental biologist at the Mount Desert Island Biological Laboratory in Salisbury Cove, Maine.

  2. New Planet: Not Too Hot, Not Too Cold

    Just right.

    Artist's impression of Kepler-22b.


    For the first time, astronomers have used the Kepler space telescope to spot a planet smack in the middle of the habitable zone of its sunlike star, where temperatures are good for life. The planet, named Kepler-22b, is 2.4 times the size of Earth and 600 light-years away, researchers announced on 5 December at the start of the 5-day First Kepler Science Conference at the NASA Ames Research Center in California. “If this planet has a surface, it would have a very nice temperature of some 70° Fahrenheit [21°C],” said NASA's William Borucki. Overall, Kepler has found 1094 new planet candidates since February 2011, researchers reported, bringing the total to a whopping 2326.

  3. Biofuel Bugs

    In the biofuels business, the idea of converting nonfood plants into fuels is like a mirage: enticing, but seemingly just out of reach. It requires a cocktail of expensive enzymes to break down the plants into sugars that microbes can easily transform into chemical precursors for gasoline, diesel, and jet fuel. Now, researchers have genetically engineered bacteria, coaxing them to produce the costly cocktail and then synthesize the fuel precursors.

    Currently, most biofuel makers use microbes to synthesize ethanol from either cornstarch or sugar from sugar cane. But these ethanol crops compete for valuable agricultural land. Biofuel brewers would prefer to convert agricultural waste or non-food plants, such as trees and grasses. But it's harder to transform that “cellulosic biomass” into fuel.

    A team led by bioengineer Jay Keasling of the Joint BioEnergy Institute in Emeryville, California, has now eased the process by inserting new genes into the bacterium Escherichia coli. In general, the genes enable the bacteria to produce enzymes that break down cellulose and hemicellulose in a common biofuels plant called switchgrass. And different versions of the E. coli were given added genes for metabolic pathways that allow the microbes to make chemical precursors for either gasoline, diesel, or jet fuel, the researchers reported online 28 November in the Proceedings of the National Academy of Sciences.

    The bugs produce only about one-tenth of the enzymes they need to break industrial quantities of cellulose and hemicellulose, however, and they don't make much fuel. To improve both measures, Keasling says his team will try engineering similar genes into yeast.