2-Acetyl-1-Pyrroline Biosynthesis: from Fragrance to a Rare Metabolic Disease

2-acetyl-1-pyrroline has been reported as a major compound responsible for pleasant aroma in basmati and other scented rice varieties. The biosynthesis of this molecule is due to deletion in the betaine aldehyde dehydrogenase2 gene. This deletion leads in the accumulation of Δ1-pyrroline which reacts non-enzymatically with methylglyoxal to form 2-acetyl-1-pyrroline. Due to non-functionality of this gene that regulates the synthesis of Gamma-amino butyric acid, the plant species synthesizing 2-acetyl-1-pyrroline suffers for the yield losses, sterility and susceptibility to biotic and abiotic stresses. Thus the non-functionality of betaine aldehyde dehydrogenase2 gene coupled with 2-acetyl-1-pyrroline synthesis serves as a metabolic disease. In this review these aspects are discussed in detail.