Abstract
Chlorophyllide a oxygenase (CAO) plays an essential role in chlorophyll b synthesis. Recently, we reported that Arabidopsis CAO is composed of three domains (A, B and C) and that the N-terminal domain (A-domain) regulates CAO protein levels in chloroplasts.
In this study, we fused the various domains with GFP and the fusion proteins were overexpressed in wild-type and ch 1-1 (chlorophyll b-less mutant) of Arabidopsis thaliana to investigate the function of A-domain. GFP-BC fusion proteins accumulated in the etioplasts and increased during greening in both wild-type and ch 1-1 backgrounds. AB-GFP proteins accumulated in the cotyledons of ch 1-1 background during greening, but the protein levels were low in wild-type background when chlorophyll a/b ratio decreased to stable level. The regulation of CAO protein levels by A-domain will be discussed.
