phyB-1 sorghum maintains responsiveness to simulated shade, irradiance and red light: far-red light. Academic Article uri icon


  • The sorghum [Sorghum bicolor (L.) Moench] phyB-1 mutant exhibits a constitutive shade-avoidance phenotype including excessive shoot elongation. It was previously shown that this mutant also overproduces ethylene. Although phytochrome B (phyB) is assumed to be the pigment most important in sensing and transducing shade signals, the sorghum phyB-1 mutant still responds to light signals characteristic of shade. Specifically, it was determined that the leaf blade : leaf sheath elongation of phyB-1 is responsive to red : far red (R : FR), but this response is opposite that of wild type (WT). Reducing the photosynthetic photon flux density (PPFD) strongly reduced the leaf blade : leaf sheath of WT but did not affect phyB-1, demonstrating a role for phyB in sensing PPFD. Using light-emitting diode (LED) lighting, it was found that WT ethylene production was increased with low R : FR while PPFD had no effect. Conversely, phyB-1 ethylene production increased only with high PPFD, high R : FR which was the treatment resulting in the least ethylene production by WT. Elevated ethylene production inhibits shoot elongation, but may contribute to shade avoidance by reducing leaf blade : leaf sheath elongation. Ethylene responses to light treatments designed to promote or reduce phytochrome A (phyA) activity, and the analysis of PHYA levels in the two cultivars suggests that phyA could be involved in transducing shade signals in light-grown sorghum. Responses potentially tranduced by phyA are elevated in phyB-1 which also over-expresses PHYA.

published proceedings

  • Plant Cell Environ

author list (cited authors)

  • Finlayson, S. A., Hays, D. B., & Morgan, P. W.

citation count

  • 16

complete list of authors

  • Finlayson, Scott A||Hays, Dirk B||Morgan, Page W

publication date

  • August 2007