Abstract
Choline monooxygenase catalyzes the oxidation of choline to betainealdehyde which is a key enzyme for the betaine synthesis in plants. Purified CMO showed extremely low activity probably due to the labile property of the enzyme. For functional characterization of CMO, we constructed the vectors in which the CDH gene of E. coli bet gene clusters was replaced with CMO or deleted, and used for the transformation of E. coli (DH5a) and fresh water cyanobacterium Synechococcus PCC7942, neither of which could synthesis betaine. We found that E. coli cells in which choline dehydrogenase (CDH) was replaced with spinach CMO accumulate betaine. Changes of Cys181 in spinach CMO to Ser, Thr, and Ala and His287 to Gly, Val, and Ala abolished the accumulation of betaine. Overexpression of spinach CMO in E. coli, Synechococcus, and Arabidopsis conferred resistance to abiotic stress. These results will be presented.
