Mechanism of 2-acetyl-1-pyrroline biosynthesis in Bassia latifolia Roxb. flowers.

The flowers of Bassia latifolia are known to contain 2-acetyl-1-pyrroline (2AP), the compound responsible for pleasant aroma in basmati and other scented rice. Four growth stages of Bassia flowers were identified and 2AP contents were analysed in each stage. It was found that 2AP (3.30 ppm) gets synthesized only in fleshy corolla of mature flowers (fourth stage). The activity of γ-aminobutyraldehyde dehydrogenase (AADH); an enzyme responsible for synthesis of γ-aminobutyricacid (GABA) from γ-aminobutyraldehyde (GABald) was assessed in these four stages. The AADH activity was absent in the fourth stage. It was concluded that ceased activity of AADH in fourth stage flowers leads to the accumulation of γ-aminobutyraldehyde which is cyclised spontaneously to Δ(1)-pyrroline, the key precursor of 2AP. Δ(1)-pyrroline further reacts unenzymatically with methylglyoxal to form 2AP.

Determination of some minerals and ß-carotene contents in aromatic indica rice (Oryza sativa L.) germplasm.

39 aromatic indica rice (Oryza sativa L.) cultivars were characterized for Iron, Zinc, Calcium, Magnesium, Copper and ß-carotene contents. The ß-carotene contents were ranging from 1.23 to 9.9µg/g in brown and 0.08 to 1.99µg/g in milled rice. Among the mineral contents, Magnesium was found ranging from 855µg/g (Gham) to maximum of 1636µg/g (Badshahbhog) followed by Iron in 32µg/g (Jirga) to 218µg/g (Kalsal), Copper content from 2µg/g (Girga) to 1004µg/g (Gham), Zinc content from 25 (Gham) to 165µg/g (Ambemohar-157) and Calcium ranged from 14µg/g (Ambemohar pandhara) to 67µg/g (Kate chinoor). The study showed that the germplasm assessed is a good source of micronutrients and can be further exploited in breeding programme.

2-Acetyl-1-pyrroline augmentation in scented indica rice (Oryza sativa L.) varieties through Δ(1)-pyrroline-5-carboxylate synthetase (P5CS) gene transformation.

2-Acetyl-1-pyrroline (2AP) has been identified as a principal aroma compound in scented rice varieties. Δ(1)-Pyrroline-5-carboxylate synthetase (P5CS) gene is reported to regulate the proline synthesis in plants and acts as the precursor of 2AP. Two scented indica rice varieties, namely Ambemohar 157 and Indrayani, were subjected to Agrobacterium tumefaciens-mediated genetic transformation containing P5CS gene. Overexpression of P5CS led to a significant increase in proline, P5CS enzyme activity and 2AP levels in transgenic calli, vegetative plant parts, and seeds over control in both the varieties. 2AP level increased more than twofold in transgenic seeds in both varieties. This is the first report of enhancement in 2AP content through overexpression of using P5CS gene, indicating the role of proline as a precursor amino acid in the biosynthesis of 2AP in scented rice.