Analysis of the effects of mepiquat chloride priming on the seedling growth-promoting in cotton under salt stress by multi-omics

A multi-omics study was conducted on cotton seedlings to determine the growth promotion caused by mepiquat chloride (MC)-priming under salt stress. MC-priming markedly alleviated salt stress inhibition in root anatomical structures, increasing seedling establishment. Comparative multi-omics analyses revealed various energy metabolic pathways as key influencers of MC-priming, explaining the alleviation of salt stress. MC-priming up-regulated key proteins and phosphorylation for triacylglycerol (TAG) mobilization, γ-aminobutyric acid (GABA) shunt, and adenosine triphosphate (ATP) synthesis under salt stress. The coexpression network analyses also suggested that MC-priming regulates these metabolic pathways in a mutual-functioning fashion involving salt tolerance responses. Importantly, the inhibitor of β-oxidation and GABA-synthesis disrupted the MC-priming-induced growth under salt stress, confirming the importance of these pathways in forming the MC-priming response. MC-priming significantly blocked the salt-triggered TAG accumulation and early enhanced GABA shunt activities under salt stress. Meanwhile, MC-priming improved energy efficiency by up-regulating ATP synthase and down-regulating cytochrome b5-like reductase, thereby enhancing ATP formation and reducing reactive oxygen species production. In addition, MC-priming enhanced antioxidant enzymatic activities under salt stress. These findings provide insights into the energy regulatory pathway of MC-priming that mediates growth-promotion under salt stress. Thus, this study reinforces the potential of MC-priming to improve cotton seed germination under salt stress.