Transient down-regulation of phytochrome mRNA abundance in etiolated cucumber cotyledons in response to continuous white light.

Phytochrome mRNA abundance decreased to 20% of the initial level in etiolated cucumber (Cucumis sativus L.) cotyledons exposed to continuous white light. Unexpectedly, by 12 hours of continuous white light, phytochrome mRNA had reaccumulated to 60% of the control level. High stringency RNA blot analyses suggest that it is the mRNA encoding type I phytochrome that reaccumulates.