Glycine Betaine (GB) is an organic compound which acts as compatible solute for plant acclimation to various types of abiotic stresses. It also stimulates the growth of plants by increasing photosynthesis rate and chlorophyll contents.

Exogenous GB supplementation significantly mitigates oxidative stress induced by Cd toxicity in cotton plant through reduction of MDA content and EL levels [81]. It also upholds the photosynthetic activities under water deficit conditions.
Osmoprotectant

Glycine betaine (GB) is a major component of human urine and has been shown to protect bacteria from hypertonic salt stress. GB is produced by the oxidation of choline in the liver and then transported across the membrane into the kidney. This osmoprotective property has been demonstrated for enteric bacteria such as E. coli.

The synthesis of GB is regulated by a set of enzymes, including two choline aldehyde dehydrogenases. These metabolize choline to form betaine aldehyde, which is then converted by the two GB synthases into GB and acetylcholine. This osmoprotective function of GB has made it a popular choice as a dietary supplement.

In the mung bean rhizosphere, bacterial isolates that accumulated GB exhibited enhanced resilience to salinity stress. These rhizobacteria also produced a number of other secondary metabolites, which may help them counteract the negative effects of salinity stress. The osmoprotective capacity of GB has prompted scientists to explore the possibility of engineering this molecule into crops that naturally lack it.
Antioxidant

Glycine Betaine is an organic compound with a dipolar molecular structure that allows it to interact with both the hydrophilic and hydrophobic regions of proteins and other macromolecules. This is why it has been found to be effective as an antioxidant, protecting cells from damage by reactive oxygen species (ROS) that are induced by various stresses.

It is an amphoteric quaternary ammonium molecule and is electrically neutral at physiological pH. It is derived from choline and is synthesized in plants through two pathways, one involving N-methylation of glycine and the other involving oxidation of choline by a soluble NAD+-dependent choline aldehyde dehydrogenase to produce betaine aldehyde.

GB can significantly mitigate salt stress in plants by enhancing levels of compatible solutes, reducing membrane damage and oxidative stress and regulating activities of antioxidant enzymes. Moreover, it can enhance the tolerance of plants to high temperature by adjusting cell membrane permeability and osmotic adjustment. It also increases root and shoot growth, leaf number, stomatal conductance, photosynthetic rate (Pn), relative water content (RWC) and soluble protein (SP) accumulation.
Growth Promoter

Glycine betaine (GB) is an N,N’-trimethylglycine quaternary ammonium compound that is produced in many organisms including plant species. It is a vital compatible osmolyte that plays critical roles in osmoregulation, maintaining membrane integrity against various stresses and scavenging ROS. Many halophytes and certain crop plants have the capacity to naturally accumulate GB. However, the mechanism by which they do so has not been elucidated.

GB is produced in two pathways involving either the N methylation of choline or the oxidation of glycine to betaine aldehyde by a choline betaine dehydrogenase. In plants, synthesis of GB is regulated by both chloroplasts and the cytosol. The accumulation of GB in the chloroplast is positively correlated with stress tolerance, while that in the cytosol does not.

Stress Reliever

The accumulation of glycine betaine (GB; N,N,N-trimethyl glycine) in cells acts as an osmolyte and protects bacteria and some plant species from osmotic stress. In addition, GB reduces membrane-lipid peroxidation and increases the activity of antioxidant enzymes.

In organisms that cannot synthesize de novo solutes, the size of intracellular betaine pools is regulated by balancing uptake with catabolism or export. For example, P. syringae uptakes betaine during hyperosmotic stress and the resulting accumulation is balanced by catabolism. This balancing is also demonstrated by the observed higher betaine levels in the gbcAB catabolic mutant.

The changes in foliar GB concentrations among seedlings that survived and succumbed to post-freeze exposure suggest that glycine betaine accumulation is an adaptation for cold tolerance. The magnitude of the change in GB was not significantly influenced by source region or freeze exposure location, suggesting that this adaptation is common to all A. germinans populations in the study area.