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This experiment was carried out to provide a comprehensive insight into the protein activities involved in dormancy establishment in seeds of common cocklebur (Xanthium strumarium), an annual plant with two dimorphic seeds contained in one casing known as a burr. These consist of a smaller dormant seed and a larger non‐dormant seed. The proteome profile was compared between developing dormant and non‐dormant seeds of Xanthium strumarium at five consecutive stages including three, 10, 20, 30, and 45 days after burr emergence (stages 1 to 5). We identified 6524 proteins in total, and approximately 3.6% of these were differentially abundant proteins (DAPs) between the two seed types. Both seed types showed fundamental changes in developmental programs during the examined stages. More than 38% of all DAPs were observed at the first stage, supporting the importance of the early developmental stage in seed fate determination. The detected DAPs at stage 1 were mainly associated with the cell division phase, which showed a delay in the dormant seeds. Over‐representation of proteins responsible for cell wall biosynthesis, cytokinesis, and seed development were detected for non‐dormant seeds at the first stage, while dormancy‐associated proteins showed less abundance. Stage 3 was the critical stage for switching processes toward seed maturation and abscisic acid (ABA) signaling. Interestingly, higher abundance proteins in the mature non‐dormant seed were mainly involved in the facilitation of seed germination. Taken together, the temporal pattern of the accumulated proteins in developing dormant seeds demonstrated a delay in the initiation of active cell division, enriched response to ABA, and defects in seed maturation. Moreover, stored proteins in the mature dormant seed delay germination but not dormancy induction. Finally, our results suggest that dormancy may be established at a stage of seed development earlier than previously thought. [ABSTRACT FROM AUTHOR]

Seed dormancy ensures plant survival but many mechanisms remain unclear. A high-throughput RNA-seq analysis investigated the mechanisms involved in the establishment of dormancy in dimorphic seeds of Xanthium strumarium (L.) developing in one single burr. Results showed that DOG1, the main dormancy gene in Arabidopsis thaliana L., was over-represented in the dormant seed leading to the formation of two seeds with different cell wall properties. Less expression of DME/EMB1649, UBP26, EMF2, MOM, SNL2, and AGO4 in the non-dormant seed was observed, which function in the chromatin remodelling of dormancy-associated genes through DNA methylation. However, higher levels of ATXR7/SDG25, ELF6, and JMJ16/PKDM7D in the nondormant seed that act at the level of histone demethylation and activate germination were found. Dramatically lower expression in the splicing factors SUA, PWI, and FY in non-dormant seed may indicate that variation in RNA splicing for ABA sensitivity and transcriptional elongation control of DOG1 is of importance for inducing seed dormancy. Seed size and germination may be influenced by respiratory factors, and alterations in ABA content and auxin distribution and responses. TOR (a serine/threonine-protein kinase) is likely at the centre of a regulatory hub controlling seed metabolism, maturation, and germination. Over-representation of the respirationassociated genes (ACO3, PEPC3, and D2HGDH) was detected in non-dormant seed, suggesting differential energy supplies in the two seeds. Degradation of ABA biosynthesis and/or proper auxin signalling in the large seed may control germinability, and suppression of endoreduplication in the small seed may be a mechanism for cell differentiation and cell size determination. [ABSTRACT FROM AUTHOR]