Any amateur gardener knows plants need two things to survive: sunlight and water. But tweak a few genes and those basic requirements can diminish or even disappear. At least that's what two teams of researchers report in today's issue of Science.

The first group¿from Martek Biosciences Corporation and the Carnegie Institution of Washington¿manipulated genes to wean a type of microalgae, called Phaeodactylum tricornutum, from the sun. To do so, they had to provide these single-celled aquatic plants with an alternative source of energy¿which they did by inserting a gene encoding for a glucose transporter. They found that algae altered with the gene for a human glucose transporter grew in dark fermenters at densities 15 times that of sunlight-grown algae. In addition, these tiny plants¿which are used in a number of dietary supplements¿were less likely to become contaminated.

The second group identified a gene that controls water retention and cell division in the plant kingdom's equivalent to a guinea pig, Arabidopsis thaliana. Alan Jones and his colleagues at the University of North Carolina, Chapel Hill, mutated a gene encoding a so-called G-protein, which regulates many plant processes. Because the resulting plants wilted more quickly than control crops, though, they guessed that the gene also affected water retention. Sarah Assmann's lab at Penn State University found out how: plants lacking the gene didn't respond to a hormone, abscisic acid, that regulates the size of openings in leaves called stomatal pores. If a plant cannot close these pores during times of drought, it will lose water rapidly and expire.

"When I was born in 1957, there were four billion people on Earth," Jones says, "and if I die a natural death sometime around 2030, there will be about 10 billion. That's an enormous increase in just one lifetime. If we are going to be able to feed all these people, we're going to figure out ways of improving and increasing the food supply by nontraditional means. We think this work is an important step toward doing that because researchers should be able to modify this gene to make crops hardier."

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