Submitted to: Nature
Publication Type: Review Article
Publication Acceptance Date: 2/1/2002
Publication Date: 2/1/2002
Citation: Quail, P.H. 2002. Phytochrome photosensory signalling networks. Nature, 3(2):85-93. Interpretive Summary: The phytochromes comprise a small family of sensory photoreceptors (with five members in Arabidopsis, designated phyA¿phyE), which monitor informational light signals in the environment and modulate appropriate growth and development responses through induced changes in gene expression. Individual family members have different, albeit frequently partially overlapping, photosensory and/or physiological functional roles in regulating plant responses to light. Five principal developments in recent years have substantially influenced current concepts of the cellular, molecular and biochemical mechanisms by which the phytochromes perceive and transduce light signals to photoresponsive nuclear genes: --light-induced nuclear translocation of phytochrome molecules; --direct interaction of phytochrome molecules with a DNA-bound transcription factor; --transcription-factor genes are early targets of phytochrome signalling; --phytochrome-associated protein kinase activity; --post-translational regulation of signalling through targeted degradation of a key transcriptional regulator. Evidence so far indicates that the phytochromes might use at least two pathways to signal to photoresponsive genes: a primary, early-response pathway, which involves transcriptional regulation by direct targeting of light signals to responsive promoters; and a secondary, longer-term pathway, which involves abrogation of targeted proteolytic degradation of a key transcription factor. Future research efforts can be expected to exploit the unprecedented power that is offered by the combination of mutants and microarrays for the dissection of photosensory signalling and transcriptional networks.
Technical Abstract: Light is life for plants. To continuously assess and adapt to fluctuations in the quality and quantity of this essential commodity, plants deploy sensory photoreceptors, including the phytochromes. Having captured an incoming photon, the activated phytochrome molecule must relay this information to nuclear genes that are poised to respond by directing appropriate adjustments in growth and development. Defining the intricate intracellular signalling networks through which this sensory information is transduced is an area of intense research activity.