Phytochromes are Pr-ipatetic kinases

A series of new studies reveal how the red/far-red light photoreceptors cal led phytochromes act. Phytochrome A and phytochrome B each move to the nucl eus when activated by light, and phytochrome A is a kinase. Phytochrome-int eracting proteins provide candidate signal transduction components and a re cent physiological study suggests how phyA may mediate responses to far-red light. Regulation of phytochrome nuclear localization and kinase activitie s creates multiple phytochrome species, which may each have different regul atory activities.