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Plant biologists have been working for years to nail down the series of chemical signals that one class of plant hormones, called brassinosteroids, send from a protein on the surface of a plant cell to the cell’s nucleus. New research has isolated another link in this chain. Fully understanding the brassinosteroid pathway could help scientists better understand plant growth and help improve food and energy crop production.

The ability of embryonic stem cells to differentiate into different types of cells with different functions is regulated and maintained by a complex series of chemical interactions, which are not well understood. Learning more about this process could prove useful for stem cell-based therapies down the road. New research from a team led by Carnegie’s Yixian Zheng zeroes in on the process by which stem cells maintain their proper undifferentiated state.

Plants are very sensitive to light conditions, in part due to a signal that activates some special photoreceptors that regulate growth, metabolism, and physiological development. Scientists believe that these light signals control plant growth and development by activating or inhibiting plant hormones. New research from Carnegie plant biologists has altered the prevailing theory on how light signals and hormones interact. Their findings could have implications for food crop production.

Plants grow upward from a tip of undifferentiated tissue called the shoot apical meristem. As the tip extends, stem cells at the center of the meristem divide and increase in numbers. But the cells on the periphery differentiate to form plant organs, such as leaves and flowers. In between these two layers, a group of boundary cells go into a quiescent state and form a barrier that not only separates stem cells from differentiating cells, but eventually forms the borders that separate the plant’s organs. Because each plant's form and shape is determined by organ formation and organ boundary creation, elucidating the underlying mechanisms that govern these functions could help scientists design the architecture of crop plants to better capture light and ultimately produce more crop yield with less input.

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Until now, Earth was the only planet known to have vast reservoirs of water in its interior. Scientists analyzed the water content of two Martian meteorites originating from inside the Red Planet. They found that the amount of water in places of the Martian mantle is vastly larger than previous estimates and is similar to that of Earth’s. The results not only affect what we know about the geologic history of Mars, but also have implications for how water got to the Martian surface. The data raise the possibility that Mars could have sustained life.

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Scientists at Plant Biology, with colleagues,* have found that a plant steroid prompts two genes to battle each other—one suppresses the other to ensure that leaves grow normally in rice and the experimental plant Arabidopsis thaliana, a relative of mustard. The results, published in the December 15, 2009, issue of The Plant Cell, have important implications for understanding how to manipulate crop growth and yield.