Abstract
Phototropin (phot) is a plant blue light photoreceptor of about 110 kDa consisting of the N-terminal chromo domain and the C-terminal kinase domain. The signal transduction mechanism of phot remains unknown. We have recently identified a phot in the green algae, Chlamydomonas reinhardtii. To investigate the biological activity of Chlamydomonas phot (Crphot), we expressed it in the Arabidopsis phot1 phot2 mutant and examined whether it complemented the mutation. The results indicated that phot responses were restored in the lines expressing Crphot at a high level. Hence, certain aspects of signal transduction appear to be conserved between two distantly related species. We then examined roles for the kinase domain. The full-length phot and its kinase domain were expressed in the Cytotrap yeast two-hybrid system. Consequently, the kinase domain has been shown to have membrane localization activity. We are currently investigating the mechanism and functional significance of this activity.
