Physiological and proteomic analyses for seed dormancy and release in the perennial grass of Leymus chinensis

Seed dormancy is an important trait determining seed germination and seedling establishment of plants. Despite extensive studies on seed dormancy, relatively few studies have specifically focused on mechanisms underlying seed dormancy in wild perennial species. Leymus chinensis is a perennial grass forage with excellent nutritional value and one of the dominant species in the Eurasian steppe. In this study, the proteomic features for seed dormancy and release in the wild germplasm after ripening were analyzed by iTRAQ technology. Based on the wheat (Triticum aestivum) protein database, a total of 281 differently expressed proteins were identified in L. chinensis non-dormant seeds versus dormant seeds, with 188 differentially decreased (fold change < 0.8, P < 0.05) and 93 differentially increased proteins (fold change > 1.2, P < 0.05). Based on the COG annotation, the proteins involved in chromatin structure and dynamics, intracellular trafficking, section, and vesicular transport, cytoskeleton were all increased differentially. In contrast, the proteins involved in RNA processing and modification, cell wall/membrane/envelope biogenesis, and signal transduction mechanisms were all decreased differentially. Based on the Mapman annotation and function enrichment, the decreased proteins mainly participated in photosynthesis and TCA cycle, while the increased proteins were involved in protein targeting, degradation, and synthesis, amino acid metabolism, lipid metabolism, redox, cell cycle, and DNA synthesis/chromatin structure. After-ripening of L. chinensis dormant seeds was the transition from maturation to storage. Our proteomic analyses revealed that the dormancy release of L. chinensis seeds was related to the increases in tubulin, histone, and thioredoxins, and the decrease in L- ascorbate peroxidase. Based on these results, we proposed that an increase in reactive oxygen species (ROS) during after-ripening is an important driver to regulate dormancy release in L. chinensis seeds by modulating cytoskeleton and chromatin. These findings provide new insight for our mechanistic understanding of dormancy control in perennial grass forage.