Dielectric Barrier Discharge Cold Plasma Improves Storage Stability in Paddy Rice by Activating the Phenylpropanoid Biosynthesis Pathway

A nonthermal pretreatment using dielectric barrier discharge
cold
plasma (DBD-CP) was developed to improve the stress resistance of
paddy rice during postharvest storage. The physicochemical properties,
bioactive characteristics, and secondary metabolites of paddy rice
were assessed after applying an optimized DBD-CP procedure, with enzyme
activities and gene expression monitored over a 60 day storage period
at 35 °C. A 17.06% reduction in the total color change index
was noted in the DBD-CP group. Bioactive compounds, particularly gallic
acid, were significantly increased, enhancing the defense mechanisms
against high-temperature stress. Nontargeted metabolomics analysis
indicated an upregulation of phenylpropanoid metabolism in DBD-CP-treated
rice compared to controls, with notable increases in secondary metabolites
such as coumaric acid, caffeic acid, and sinapic acid, suggesting
potential biomarkers for stress resistance. Further verification showed
significant enhancements in key enzymes of phenylpropanoid metabolism,
including phenylalanine ammonia lyase (PAL), cinnamic acid-4-hydroxylase
(C4H), plant coumaric acid-3-hydroxylase (C3H), and cinnamyl alcohol
dehydrogenase (CAD), with increases ranging from 1.71 to 2.28 times.
Gene expression levels of OsPAL7, OsC4H4, and OsCAD2 aligned with these enzymatic changes
post-DBD-CP treatment. In conclusion, DBD-CP treatment can modulate
phenylpropanoid metabolism in paddy rice, thereby enhancing bioactive
compound levels to reduce stress damage during high-temperature storage.