Transcriptional response of glycinebetaine-related genes to salt stress and light in leaf beet

Beta vulgaris L. accumulates a large amount of glycinebetaine (betaine), a metabolite that is related to salt- tolerance. Production of betaine involves expression of many genes that encode enzymes such as betaine aldehyde dehydrogenase, choline monooxygenase, phosphoethanolamine N-methyltransferase, S-adenosyl-L-methionine synthetase, S-adenosyl-L-homocysteine hydrolase, and methionine synthase. We examined transcriptional regulation of the betaine- related genes in leaf beet (Beta vulgaris L. var cicla, cv. shirogukifudanna). Transcript expression of these betaine-related genes in leaf tissue had the following common features: (1) a similar pattern of transcript induction under salt stress, (2) reduced induction under salt stress in a dark condition, and (3) diurnal rhythms of transcript levels under a photoperiod of 16 h light/8 h darkness. The co-regulation of transcripts may contribute to the effective betaine production without disturbing the biosynthesis of other products in leaf beet.