Poster: Photomorphogenesis

Abs # 517: Association of blue light-dependent phosphorylation with the function of arabidopsis cryptochrome 1 and cryptochrome 2

Presenter:	Maymon, Maskit , maskit@ucla.edu
Authors	Maymon, Maskit  (A)   Dror Shalitin,   (A)   Xuhong Yu,   (A)   Todd Mockler,   (A) (B)  Hongyun Yang,   (A)   Hongwei Guo,   (A) (B)  Gary C. Whitelam,   (C)   Chentao Lin,   (A)
Affiliations:	(A): ucla (B): salk institute (C): university of leicester, uk

Cryptochromes are photolyase-like blue/UV A light receptors that regulate various light responses in animals and plants. Arabidopsis cryptochrome 1 (cry1) is the major photoreceptor mediating blue light inhibition of hypocotyls elongation, while cryptochrome 2 (cry2) mediates light regulation of seedling development and photoperiodic flowering. Here we report that both cry1 and cry2 undergo a blue-light dependent phosphorylation. Cry1 is detected primarily as an unphosphorylated protein in etiolated seedlings, but is phosphorylated in plants exposed to blue light. Cry1 phosphorylation increases in response to elevations in blue light intensities, whereas phosphorylated cry1 rapidly disappears upon transfer of plants from light to dark. Little cry1 phosphorylation is detected in seedlings treated with red or far-red light, and phytochrome mutations show no significant effect on the blue-light dependent phosphorylation of cry1, suggesting that phytochromes might not be directly involved in cry1 phosphorylation. Missense cry1 mutants that express full-length CRY1 apoprotein do not show blue light-induced phosphorylation. Similarly, our results suggest that cry2, in the absence of light, remains unphosphorylated, inactive and stable. No phosphorylation has been detected in red or far-red light, and single, double and triple phytochrome mutants do not seem to affect cry2 phosphorylation. Fluence-rate is closely associated with cry2 phosphorylation, however, a further increase of fluence results in decreased phosphorylation. Overall, our data suggest that blue-light dependent phosphorylation of cry1 and cry2 triggers photomorphogenic responses that are closely associated with the photoreceptors function and structure.