Application of saline to seeds enhances the biosynthesis of 2-acetyl-1-pyrroline in aromatic rice seedlings ( Oryza sativa L.)

Salinity was shown to impact the formation of 2-acetyl-1-pyrroline (2-AP), the key flavour compound in aromatic rice cultivars. To study the effects of saline application to seeds on 2-AP biosynthesis in aromatic rice and to further investigate the enzymatic and molecular mechanisms involved, the present study was conducted with nine treatments. The seeds of three aromatic rice cultivars were primed or soaked in 0.01, 0.02, 0.05 and 0.10 mM sodium chloride solutions, and the seeds that were both primed and soaked in distilled water were considered the control group. Then, the seedlings were allowed to grow in an artificial climate box. The results showed that both priming and soaking seeds with saline significantly increased the 2-AP content in aromatic rice seedlings. The highest 2-AP content was recorded in the seeds primed with 0.10 mM sodium chloride. In the seeds treated with saline, increased amounts of proline, P5C and Δ1-pyrroline were observed and resulted in enhanced 2-AP biosynthesis through induced gene expression (P5CS1, P5CS2 and PRODH) and activities of enzymes including PDH and P5CS. In summary, application of saline to seeds increased 2-AP content in aromatic rice seedlings by up-regulating the related precursors contents, enzymes activities and genes expression.