Photoactivation and inactivation of Arabidopsis cryptochrome 2

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Science  21 Oct 2016:
Vol. 354, Issue 6310, pp. 343-347
DOI: 10.1126/science.aaf9030

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Turning off the blue-light response

In plants, blue light is perceived by cryptochromes, which, once activated, set off signaling events that regulate gene expression, circadian rhythms, and photomorphogenesis. Wang et al. now show that in the model plant Arabidopsis, one of the functions of activated cryptochromes, which are dimers or oligomers when active, is to activate production of the protein BIC1 (blue-light inhibitor of cryptochromes 1) (see the Perspective by Fankhauser and Ulm). BIC1 then favors monomerization and thus inactivation of the cryptochromes. This feedback loop resets the system so that blue-light responses can be turned off as well as turned on.

Science, this issue p. 343; see also p. 282


Cryptochromes are blue-light receptors that regulate development and the circadian clock in plants and animals. We found that Arabidopsis cryptochrome 2 (CRY2) undergoes blue light–dependent homodimerization to become physiologically active. We identified BIC1 (blue-light inhibitor of cryptochromes 1) as an inhibitor of plant cryptochromes that binds to CRY2 to suppress the blue light–dependent dimerization, photobody formation, phosphorylation, degradation, and physiological activities of CRY2. We hypothesize that regulated dimerization governs homeostasis of the active cryptochromes in plants and other evolutionary lineages.

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