Abstract
Chlorophyllide a oxygenase is a rieske-type monooxygenase that catalyzes conversion of chlorophyll a to chlorophyll b. It has been demonstrated that the levels of CAO protein control accumulation of chlorophyll b. CAO protein is consisted of three domains, namely, A, B and C domains. We hypothesized that A and B domains are involved in the regulation of the CAO levels, while C domain has a catalytic function. In order to identify the functions of A and B domains, we constructed a series of modified CAO sequences that were fused with GFP and overexpressed them in Arabidopsis thaliana. We analyzed the CAO protein levels in these transgenic plants by confocal microscopy and immunoblotting, and found that the B domain is not necessary for the regulation of the CAO protein levels, although this domain contains a phydrophylic region that resembles the PEST sequences known as the targets of the ubiquitin degradation system.
