Phytochrome has fascinated plant scientists since its discovery in 1959-1960 by the Beltsville research group of the United States Department of Agriculture. Studies in the first 20 years had evidenced that phytochrome acts as an universal regulator in plant life adapting its behavior to the environmental light, and developed widely the physiological understanding of phytochrome action. In the following 20 years, some thirty world_wide major laboratories have published over two hundred papers a year on various aspects of the subject, and they are making steady progress. The authors’ work has also contributed to the following aspects: coaction of phytochrome and phytohormone in photomorphogenesis, phytochrome purification, phytochrome regulation of male fertility, as well as phytochrome A gene analysis and expression in photoperiod sensitive genic male sterile rice. In the recent decade significant advances have been made in studies on phytochrome molecules, genes and signal transduction in phytochrome response. This is largely due to the advances in molecular genetics, where experiments using mutants and transgenic plants, particularly in Arabidopsis, that have led to the significant insights at the molecular level. The topics in this review include:(1) Discovery of phytochrome; (2) Functions of phytochrome; (3) Phytochrome molecules; (4) Phytochrome regulation in gene expression.
