Catalyzes the first step of the osmoprotectant glycine betaine synthesis. choline + 2 H(+) + O2 + 2 reduced [2Fe-2S]-[ferredoxin] = betaine aldehyde hydrate + H2O + 2 oxidized [2Fe-2S]-[ferredoxin] Binds 1 [2Fe-2S] cluster. Binds 1 Fe cation. Amine and polyamine biosynthesis; betaine biosynthesis via choline pathway; betaine aldehyde from choline (monooxygenase route): step 1/1. Expressed in roots and leaves. By salt and drought stress. Belongs to the choline monooxygenase family.