Proteomic analysis of Arabidopsis seed germination and priming

To better understand seed germination, a complex developmental process, we developed a proteome analysis of the model plant Arabidopsis for which comp lete genome sequence is now available. Among about 1,300 total seed protein s resolved in two-dimensional gels, changes in the abundance (up- and down- regulation) of 74 proteins were observed during germination sensu stricto ( i.e. prior to radicle emergence) and the radicle protrusion step. This appr oach was also used to analyze protein changes occurring during industrial s eed pretreatments such as priming that accelerate seed germination and impr ove seedling uniformity. Several proteins were identified by matrix-assiste d laser-desorption ionization time of flight mass spectrometry. Some of the m had previously been shown to play a role during germination and/or primin g in several plant species, a finding that underlines the usefulness of usi ng Arabidopsis as a model system for molecular analysis of seed quality. Fu rthermore, the present study, carried out at the protein level, validates p revious results obtained at the level of gene expression (e.g. from quantit ation of differentially expressed mRNAs or analyses of promoter/reporter co nstructs). Finally, this approach revealed new proteins associated with the different phases of seed germination and priming. Some of them are involve d either in the imbibition process of the seeds (such as an actin isoform o r a WD-40 repeat protein) or in the seed dehydration process (e.g. cytosoli c glyceraldehyde-3-phosphate dehydrogenase). These facts highlight the powe r of proteomics to unravel specific features of complex developmental proce sses such as germination and to detect protein markers that can be used to characterize seed vigor of commercial seed lots and to develop and monitor priming treatments.