| The survival of plants is highly dependent upon their ability to respond morphologically to environmental variations in light conditions. This developmental plasticity is a result of complex interactions of internal signaling cascades initiated by the absorption of external light signals. The absorption of light is accomplished by photoreceptors that perceive far-red/red, blue/UV-A, and UV-B light. The internal signaling cascades that follow the initial absorption of light are a result of gene activation, gene repression and biochemical signaling. However, the precise steps in the pathway from photoperception to a photosynthetically active plant are largely unknown.; Our understanding of the light signaling processes involved in the development of plants is increasing. The use of mutants with altered light or dark-grown phenotypes as indicators of genetic loci involved in plant development have been extremely important in the progress made in understanding photomorphogenesis. The specific aim of this research was to isolate and characterize new mutations within the phytochrome A light signal transduction pathway. A novel component of the phytochrome A pathway, fry2 (f&barbelow;ar-r&barbelow;ed elongated hy&barbelow;pocotyl), has been identified in Arabidopsis . This mutant shows an elongated phenotype specific to far-red light indicating that the genetic locus is specifically involved in phytochrome A signaling. In addition, fry1, a dominant allele of PHYA was identified. The dominant nature of this mutation suggests that the mutated region of the protein is critical for PHYA function. Molecular analysis revealed that this mutation is caused by a single amino acid change at position 631 from valine to methionine. The two mutant seedlings recovered during this research have greatly advanced our understanding of the phytochrome A signaling pathway. |
