Dielectric Barrier\nDischarge Cold Plasma Improves\nStorage Stability in Paddy Rice by Activating the Phenylpropanoid\nBiosynthesis Pathway

A nonthermal pretreatment using dielectric barrier discharge\ncold\nplasma (DBD-CP) was developed to improve the stress resistance of\npaddy rice during postharvest storage. The physicochemical properties,\nbioactive characteristics, and secondary metabolites of paddy rice\nwere assessed after applying an optimized DBD-CP procedure, with enzyme\nactivities and gene expression monitored over a 60 day storage period\nat 35 °C. A 17.06% reduction in the total color change index\nwas noted in the DBD-CP group. Bioactive compounds, particularly gallic\nacid, were significantly increased, enhancing the defense mechanisms\nagainst high-temperature stress. Nontargeted metabolomics analysis\nindicated an upregulation of phenylpropanoid metabolism in DBD-CP-treated\nrice compared to controls, with notable increases in secondary metabolites\nsuch as coumaric acid, caffeic acid, and sinapic acid, suggesting\npotential biomarkers for stress resistance. Further verification showed\nsignificant enhancements in key enzymes of phenylpropanoid metabolism,\nincluding phenylalanine ammonia lyase (PAL), cinnamic acid-4-hydroxylase\n(C4H), plant coumaric acid-3-hydroxylase (C3H), and cinnamyl alcohol\ndehydrogenase (CAD), with increases ranging from 1.71 to 2.28 times.\nGene expression levels of <i>OsPAL7</i>, <i>OsC4H4</i>, and <i>OsCAD2</i> aligned with these enzymatic changes\npost-DBD-CP treatment. In conclusion, DBD-CP treatment can modulate\nphenylpropanoid metabolism in paddy rice, thereby enhancing bioactive\ncompound levels to reduce stress damage during high-temperature storage.