Abstract: Phytoehrome is one of the most important photoreceptors in plants and plays a pivotal role in plant growth and development. GTP-binding protein, calcium-calmodulin, cGMP and the COP- DET-FUSCA molecules are signaling intermediates in phototransduction. Scientists focus efforts on defining the biochemical mechanism of phytochrome action and the signal transduction pathway from photoperception to gene expression, as well as understanding the nature, structure and fimction of phytochrome. Evidence indicates that the amino-terminal domain determines the photosensory specificity whereas the carboxyl-tenninal domain transfers signals to the downstream components.

Key words: Phytochrome, Photoregulation, Camodulin, Gene expression