Peptidomic Analysis of Tobacco Seeds with Variable Plumpness Reveals Development-Associated Peptides and Proteins

Seed plumpness is a key trait influencing germination vigor and seedling establishment quality. To elucidate the molecular mechanisms underlying tobacco seed development and facilitate the breeding of high-vigor seeds, this study characterized and analyzed the peptidome of tobacco seeds exhibiting different plumpness levels. Plump seeds demonstrated highly significant superiority over non-plump seeds in germination potential, germination rate, germination index, root length, vigor index, and 1000-seed weight. Interestingly, germination time did not differ significantly between the groups. We identified a total of 523 differentially expressed polypeptides (DEPs), comprising 284 up-regulated (corresponding to 65 proteins) and 239 down-regulated polypeptides (corresponding to 68 proteins).Functional enrichment analysis (GO) of the proteins corresponding to these DEPs revealed significant enrichment in biological processes including embryogenesis, seed development, reproductive processes, and the catabolism of amino acids, carboxylic acids, and organic acids. Pathway enrichment analysis (KEGG) indicated significant involvement in amino acid metabolism, lipid metabolism, carbohydrate metabolism, MAPK signaling, and secondary metabolite synthesis pathways. The study identified 11 key seed development-associated proteins (such as late embryogenesis abundant (LEA) proteins, glutathione reductase-like proteins, small hydrophilic plant seed proteins, and aldehyde dehydrogenases) that were all up-regulated in non-plump seeds. Concurrently, 6 signal peptide-related proteins (including glycine-rich protein precursor, 2S sulfur-rich seed storage protein, and phosphatidylinositol transfer protein) were identified. Among these, the glycine-rich protein precursor and Nitab4.5_0002257g0090 were up-regulated in non-plump seeds, while the others were up-regulated in plump seeds.