2,4-Epibrassinolide delays lignification, softening, and quality deterioration during asparagus storage

Asparagus is prone to weight loss and aging after harvest. 2,4-Epibrassinolide (EBR), a brassinosteroid hormone, is widely involved in plant growth, development, and stress response. This study investigated the effects of different EBR treatments (0, 2.5, 5, 7.5, 10, and 15 μmol L⁻¹) on the sensory quality and biochemical substance content of asparagus stored at 4°C for 5, 10, 15, 20, and 25 d. The results showed that EBR application effectively mitigates weight loss and quality deterioration during storage. This effect was evidenced by higher firmness, total chlorophyll content, soluble protein, total saponins, mechanical tissue thickness, and lower lignin content and malondialdehyde levels. Moreover, EBR enhances the antioxidant capacity of asparagus by regulating the enzymatic antioxidant system (superoxide dismutase, catalase, peroxidase, and polyphenol oxidase activities) and the non-enzymatic antioxidant system (DPPH free radical scavenging ability, vitamin C, total phenol, total flavonoids, rutin, amino acids, and proline content), thus, reducing oxidative damage. Furthermore, transcriptome analysis revealed that the softening and aging of asparagus are closely related to phenylpropanoid biosynthesis and starch and sucrose metabolism. 2,4-Epibrassinolide inhibits lignification by reducing the expression of lignin synthesis-related genes (PAL, C4H, 4CL, COMT, CCR, CAD, and POD). Additionally, EBR delays asparagus softening by suppressing cell wall degradation-related genes (Egase, β-BGL, PE, and PG). Weighted Gene Co-expression Network Analysis (WGCNA) identified 12 lignification-related candidate genes and five softening-related candidate genes. Additionally, the RT-qPCR expression of the 17 candidate genes was consistent with the transcriptome results. Altogether, this study provides a basis for EBR application in asparagus storage and preservation and offers insights into the molecular mechanisms by which EBR delays lignification and softening in asparagus.