Study Of The Degradation Mechanism Of Arabidopsis Cryptochrome 1

Plants sense different wavelength of light by different photoreceptors,which mediate light regulation of gene expression to modulate plant growth and development.Cryptochromes(CRY)are blue light receptors in plants,which mainly involves in inhibition of hypocotyl elongation and promotion of floral initiation.There are two cryptochromes in Arabidopsis-CRY1 and CRY2.Cryptochromes exist as inactive monomers in the dark,and photoexcited upon blue light illumination.Photoexcited cryptochromes undergo homooligomerization to become biochemically and physiologically active.The CRY homooligomers then interacts with CRY-interacting proteins to regulate gene expression so as to regulate plant light responses.CRY homooligomers also undergoes blue light dependent phosphorylation.Phosphorylation of CRY2 not only enhances its activity but also promotes its ubiquitination and degradation,while CRY1 is thought to be stable in blue light.Arabidopsis CRY2 localizes and completes its life cycle in the nucleus.CRY1 localizes both in the nucleus and cytosol.In order to compare the signal transduction mechanisms of nucleus CRY1 and cytosol CRY1,we have prepared NLS-CRY1 and NES-CRY1 transgenic plants,analyzed their respective physiological and photochemical activities,and have these following findings:(1)Nucleus-localized CRY1(NLS-CRY1)involves in hypocotyl elongation inhibition.(2)Both NLS-CRY1 and NES-CRY1 undergoes blue light-dependent homooligomerization.(3)Nucleus CRY1 undergoes blue light-dependent phosphorylation,unbiquitination and degradation.COP1 is responsible for nucleus CRY1 degradation.(4)Nucleus CRY1 forms photobodies in response to blue light,and the photobodies undergo liquid-liquid phase separation.(5)COP1 affects the dynamics of CRY1 liquid-liquid phase separation,and COP1 and CRY1 co-localizes to the same nuclear bodies,which implies that phase separation of nucleus CRY1 might be related to its nucleus protein degradation.Blue light-dependent degradation of nucleus CRY1 is a new signaling transduction pathway for CRY1,which inactivates or de-sensitized nucleus CRY1 to maintain appropriate photosensitivity of the cell.Further research is needed for studying the mechanisms of cytosol CRY1 signaling.