Assessment of germination, phytochemicals and transcriptional responses to ethephon-priming in soybean [Glycine max (L.) Merrill].

The present work aims to dissect the underlying signaling pathways associated with soybean [Glycine max (L.) Merrill] seed hormo-priming with ethephon (Eth). Our results demonstrated that soybean germination improved significantly upon Eth priming (Ethp). Phytohormone quantification shows relative enhanced endogenous gibberellin A4 (GA4) levels concomitant with impaired biogenesis and signaling of auxin viz. Indole acetic acid (IAA) and abscisic acid (ABA). Phytochemical analysis revealed relative reduced levels of individual and total raffinose family oligosaccharides (RFOs) components, starch, soluble sugars and sucrose concomitant with enhanced levels of reducing sugars, glucose, cellular ATP and acetyl-CoA pools. Secondary metabolite analysis revealed the activation of mevalonate (MVA) pathway with a concomitant suppression of plastidal 2-methyl-D-erythritol-4-phosphate/1-deoxy-D-xylulose-5-phosphate (MEP/DOX) and phenylpropanoid pathways, substantiated by relative reduced levels of total phenolics, tannins and proanthocyanidin. Ethp also enhances the in vitro antioxidative activity [viz. 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging ability and ferric reducing antioxidant power (FRAP)] and endogenous antioxidants levels (viz. flavonoids, isoflavones, β-carotene, vitamin C and E). Further quantitative real time-polymerase chain reaction (qRT-PCR) analysis showed transcriptional pattern of representative genes in agreement with these metabolic alterations.