Phytochrome B and the regulation of circadian ethylene production in sorghum. U sing NRI funding, Morgan and colleagues examined the role of phytochrome B, a light-sensing protein of plants, in the regulation of circadian rhythms in sorghum. A circadian rhythm is a pattern of activity, in this case ethylene production, characterized by cycles of approximately 24 hours. The cycles can be reset by environmental cues such as light.
Ethylene is a plant hormone that is an implicated regulator of plant growth.
Finlayson, Lee, and Morgan showed that normal plants that possessed phytochrome B and mutants that did not possess the protein both produced ethylene in a circadian rhythm with peak amounts during the day and low amounts at night. Normal plants grown in the shade manifested the same peaks as the mutant plants. Thus, while phytochrome B is not required for circadian timing, it appears to be involved in biosynthesis of ethylene. Because the mutant plants are taller than normal plants, this research may lead to better understanding of plant growth in general. Furthermore, it may explain how growth relates to phytochrome B, ethylene, and the circadian clock.