Abstract
Rice phytochrome family is comprised of three members, phyA, phyB and phyC. We analyzed relative levels and interactions of three phytochromes in rice (Oryza sativa cv. Nipponbare). Percent ratios of three phytochrome proteins, PHYA : PHYB : PHYC, were 84:9.5:6.5 and 57:21.5:21.5 in coleoptiles and leaves of dark-grown seedlings, respectively. However, in white light-grown seedlings the ratio was 5:65:29. The physical interactions among rice phytochromes were analyzed by co-immunoprecipitation experiments using plant extracts. Not only PHYB but also PHYA was found to be co-immunoprecipated with PHYC, which is not consistent with the results obtained in Arabidopsis. No direct physical interaction between PHYA and PHYB was detected. Formation of heterodimers between PHYB and PHYC was confirmed by gel filtration analysis. We will discuss the implications of the physical interactions between different phytochrome species in regulating plant photomorphogenesis.
