Figure 7.

Overview of the variety of blue light receptors in Chlamydomonas and the functions of pCRY. A, Overview of absorption spectra of the unusually large number of blue light receptors found in Chlamydomonas to date. The overlap in the absorption in the region of blue light (around 450 nm) presents a challenge to study overlaps in function. UV/visible absorption spectra are shown for pCRY (first 504 amino acids, overexpressed in E. coli) compared with aCRY, PHOT, ChR2 (seven-transmembrane helix domain; taken from Hegemann, 2008), and HKR1 (UV-illuminated rhodopsin fragment; taken from Luck et al., 2012). Spectra are scaled for better visibility. Contributions at greater than 510 nm for pCRY and PHOT do not originate from absorption but are caused by scattering. B, Complex formation and degradation of pCRY and its influence on clock properties and on the life cycle of Chlamydomonas. The accumulation of pCRY during the night along with its complex formation is shown. Potential unknown interaction partners are indicated by question marks (?). The proteasome-induced degradation of pCRY at early day and in the dark upon the formation of pregametes (by removal of the nitrogen source from the medium) probably trigger a signal cascade resulting in the regulation of important clock features and crucial steps in the life cycle in Chlamydomonas. Positive and negative roles of pCRY in the life cycle are indicated by + and ⁻, respectively.