Light perception in plants is mediated by photoreceptors called phytochromes for the red/far-red portions of the spectrum. Sweere et al. show that the first component in the signal transduction pathway for phytochrome B in Arabidopsis is the response regulator ARR4. Phytochrome B regulates the expression of ARR4, which in turn interacts with phytochrome B to further light signaling. Hormone-regulated expression of ARR4 and the effect of phosphorylation on its function suggest how the light signaling pathway may interact with other signaling pathways.
U. Sweere, K. Eichenberg, J. Lohrmann, V. Mira-Rodado, I. Bäurle, J. Kudla, F. Nagy, E. Schäfer, K. Harter, Interaction of the response regulator ARR4 with phytochrome B in modulating red light signaling. Science 294, 1108-1111 (2001). [Abstract] [Full Text]