How Plants Respond to Light

Plants use a series of photoreceptors to monitor the changes in their light environment, since they depend heavily on light for growth and development. The photoreceptor phyA, which specifically detects the far-red light, mediates light-responsive gene activation like seed germination, development of green pigments in leaves and flowering. Now scientists have discovered interesting new facets of light response in plants.

Upon detection of light signals, phyA accumulates in the cell cytoplasm. Two other proteins, FHY1 and FHL, bind to phyA and signal its activation. It is in the activated form that phyA can control light-responses like flowering and seed germination. The scientists discovered two transcription factors, FHY3 and FAR1,  that mediate FHY1 and FHL activity. Transcription factors (TF) are molecules that directly bind to the DNA and therefore control its expression. Moreover, the researchers discovered that accumulation of activated phyA inhibits FHY3 and FAR1 activity. This negative feedback serves as a built-in brake that limits the flow of light response.

The researchers also showed that the TFs resemble enzymes produced by jumping genes. Jumping genes are so named because they can move and insert themselves randomly in the genome. Because of this discovery the researchers are building a case that the TFs may have evolved from jumping gene material—in which may have helped the establishment and evolution of flowering plants in earth.

The full paper published by the journal Science is available at http://www.sciencemag.org/cgi/reprint/318/5854/1302.pdf Non subscribers can read the abstract at http://www.sciencemag.org/cgi/content/abstract/318/5854/1302