Integrated transcriptomics and metabolomics analysis provide insights into the alleviation of waterlogging stress in maize by exogenous spermidine application

Waterlogging stress has been found to have adverse impacts on plant growth, subsequently reducing crop yields. Spermidine (Spd), a second messenger, positively affects the growth of plants under waterlogging stress. However, the molecular mechanisms of exogenous Spd application alleviating waterlogging stress remained unclear. In this study, we performed physiological analysis and multi-omics to underlying the effect of Spd application on waterlogging stress. Spd application increased genes expression level of light-harvesting complex (LHC) and photosynthesis-related and starch-related pathway, inhibited chlorophyll degradation and maintained higher photosynthetic rate, thus increased biomass accumulation under waterlogging stress. The activation of genes related trehalose and Spd biosynthesis would result in high accumulation of trehalose and endogenous Spd. Inhibiting 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO,) expression contributed to reduced ethylene emission. All those changes increased maize resistance to waterlogging. After Spd sparying, auxin-related genes up-regulated and IAA content was increased, those favor cell elongation in maize and thus keep normal growth after Spd application under waterlogging stress. Most of genes involved in lipids were up-regulated and thus increased lipids content and protected cell membranes in maize after Spd application under waterlogging conditions. All those changes contributed to increasing the resistance to waterlogging stress. These findings broaden our understanding of the regulatory roles of Spd in alleviating waterlogging damage and will provide evidence for breeding waterlogging-tolerant maize varieties.