2. Introduction
Glycine betaine (GB) is a small, water-soluble
organic molecule that is essential to protect plants,
animals and bacteria against abiotic stress.
In plants, this molecule is essential to fight
salt,cold,heat and drought stresses.
3.
4. • Glycine betaine is an amphoteric quaternary
ammonium compound ubiquitously found in
microorganisms, higher plants and animals, and is
electrically neutral over a wide range of pH.
• Because of its unique structural features it interacts
both with hydrophobic and hydrophilic domains of
the macromolecules, such as enzymes and protein
complexes. It plays an important function in stress
condition.
5. Salinity is a major abiotic stress limiting growth
and productivity of plants in many areas of the
world due to increasing use of poor quality of
water for irrigation. Plant adaptation or tolerance to
salinity stress involves complex physiological
traits, metabolic pathways, and molecular or gene
networks.
6. Synthesis of GB
• Glycine betaine is synthesized within the cell from
either choline or glycine. Synthesis of glycine betaine
from choline is a 2-step reaction involving two or
more enzymes.
• In the first step choline is oxidized to betaine
aldehyde which is then again oxidized in the next step
to form glycine betaine. In higher plants the first
conversion is carried out by the enzyme choline
monooxygenase (CMO), whereas the next step is
catalyzed by betaine aldehyde dehydrogenase.
7.
8. Role of GB in salt tolerance
• The addition of GB to salt grown plants reduce Na
content by 40%.
• GB accumulates in the chloroplasts and plastids and
increases the tolerance of plants to salt stress.
• The physiological role of GB in alleviating osmotic
stress.
• It can also protects proteins and enzyme activities
under water stress and stabilize membranes during
freezing.
9. Increase antioxidant enzyme activity such as
SOD,APX,GR etc
Changes in photosynthesis pathway
Induction of hormones such as ABA, ethylene
Ion homeostasis
