Mizzou Scientists Discover the Game of Phototrophism

Plants do not have eyes or legs, but they have the ability to move toward or away from light, which is known as phototrophism. University of Missouri scientists reported the function of a protein in the molecular signaling pathway that controls phototrophism in plants. Two light-sensing proteins (phototrophin 1 and phototrophin 2) have been known to be involved in this mechanism, but the recent study reveals the role of another protein called NPH3.

"If the phototropic signaling pathway were like a baseball game, the phototropins would be the pitcher and NPH3 the catcher who work together to coordinate the signal, or pitch," says Mannie Liscum, a professor at the Christopher S. Bond Life Sciences Center. "Prior to this study, no one knew how NPH3 and the phototropins cooperated to facilitate the signal."

Through different genetic and biochemical techniques, the research team discovered that NPH3 modified phototrophin 1 by the addition of a small protein "tag" called ubiquitin. In the baseball analogy, ubiquitin is the hand signals of NPH3 (catcher) to communicate with phototrophin 1 (pitcher). When there is low amount of light, phototropin 1 is modified with single ubiquitin proteins and then apparently moves to a different part of the cell; if there is intensive light available, phototropin 1 is modified with multiple ubiquitin proteins and is degraded by the cell to shut down further signaling.

More information are available at http://coas.missouri.edu/news/2011/liscum.shtml.