Metabolic engineering of glycinebetaine

Abstract

Drought and salinity are among the worst scourges of agriculture. One effective mechanism to reduce damage from these stresses is the accumulation of high intracellular levels of osmoprotectant compounds. Glycinebetaine is a typical osmoprotectant. Recent studies demonstrated that the introduction of betaine accumulation pathways improves the stress tolerance of plants. Metabolic engineering is a useful technique to improve stress tolerance of important crops. The levels of betaine accumulation is determined by the rates of betaine synthesis, betaine uptake and efllux, and metabolisms. Although betaine is synthesized from choline in plants, some halotolerant cyanobacterium synthesizes betaine from glycine by three step methylation. Introduction of betaine synthesis pathways into plants have been examined. It is largely unknown how betaine is transported among plants. Only few betaine transporter genes have been isolated. In addition to the stress tolerance of plants, betaine uptake from foods would play an important role in human nutrition. As a methyl donor, betaine participates in the methionine cycle. In this review, recent progress on metabolic engineering of betaine will be described. © 2006 Springer. All Rights Reserved.