Combining phenotypic, physiological, and multi‐omics studies to provide new insights on the role of 2,4‐epibrassinolide in regulation of seed shattering in <i>Elymus sibiricus</i> L.

Abstract Background Seed shattering limits the production of Elymus sibiricus L., and application of exogenous brassinosteroid significantly alleviates plant organ abscission. Methods To explore the potential regulatory network of brassinosteroid on seed shattering, the abscission zone of E. sibiricus cv. Lanyu No. 1 treated with 2,4‐epibrassinolide (EBR) was analyzed from morphological, physiological, transcriptomic, proteomic, and histological perspectives in this study. Results As the dosage of EBR increased, the values of breaking tensile strength, auxin, gibberellin, and lignin showed a trend of an initial increase and then decrease, whereas abscisic acid levels, cellulase, and polygalacturonase activities showed the opposite trend, with significant correlations among different indicators. Differentially expressed transcripts (3645) and proteins (1124), including hub (75), and bridge (121) proteins, were identified in the abscission zone. The identified biosynthetic and metabolic pathways related to plant cell walls and hormones affect seed shattering. During abscission zone development, abscission zone cells in the control group gradually degraded, while this degradation was not significant under tested EBR doses at the same developmental stage, especially at 0.010 mg L −1 EBR. Conclusions This study provides new insights into the regulation of seed shattering in E. sibiricus by brassinosteroids, and findings will also be applicable to other Triticeae species.