Seed dormancy is a suspension of germination in seeds until the occurrence of favourable growth conditions. Xanthium strumarium L. (common cocklebur) is an annual plant with burrs containing two seeds with different dormancy characteristics. Experiencing the same environmental conditions during the development of both seeds makes X. strumarium seeds ideal candidates to study the molecular mechanisms of seed dormancy.
Proteome analysis of seed dormancy in X. strumarium was performed at 5 stages of seed development in both dormant and non-dormant seeds collected from the same burr. Proteins were extracted from dormant and non-dormant seeds at 3, 10, 20, 30 days after burr emergence as well as the mature burr. In-solution digested peptides were analysed in an ABI-Sciex TripleTOF 6600 mass spectrometer using sequential window acquisition of all theoretical fragment-ion spectra-mass spectrometry (SWATH-MS).
Our results showed out of 6524 identified proteins, 172 proteins were differentially regulated over developmental stages in both dormant and non-dormant seeds. Proteins involved in ABA (abscisic acid) signalling such as AREB3 (ABA-responsive element binding protein 3) and RAE1 (Ribonucleic Acid Export 1) were more abundant in the final stages of seed development, especially in dormant seeds. ABA has been shown to play an important role in maintenance of seed dormancy. The abundance of late embryogenesis abundant proteins (LEAs) and heat shock proteins, which are known as key indicators of seed maturity and longevity, were decreased in dormant seeds throughout the seed development. Our results provide a more detailed understanding of the changes in the proteome profile of dormancy in seeds at different stages experiencing the same environmental conditions.