Transcriptional Differences of Peanut (Arachis hypogaea L.) Seeds in the Fresh-harvest, After-ripened and Just-germinated States: insights into regulatory networks of seed dormancy-release and germination

Seed dormancy and germination are the two important traits related to plant survival and reproduction, and crop yield. To understand their regulation mechanism, it is crucial to clarify which genes or which pathways participate in the regulation of these processes. However, little information is available during the procedure of seed dormancy and germination in peanut. In this study, the seeds of the variety Luhua No.14 with non-deep dormancy were selected and its transcriptional changes at three developmental stages: the fresh-harvest (FS), the after-ripened (DS) and the just-germinated seeds (GS), were investigated by comparative transcriptomics analysis. The results showed that genes with increased transcription in DS vs FS comparison were overrepresented for oxidative phosphorylation, glycolysis pathway and tricarboxylic acid cycle (TCA), suggesting that after a period of drying storage, the intermediates stored in dry seeds were rapidly mobilized by glycolysis, TCA cycle, glyoxylate cycle, etc.; the electron transport chain accompanying with respiration has been reactivated to provide ATP for mobilization of other reserves and seed germination. In GS vs DS pairwise, dozens of the up-regulated genes were related to plant hormone biosynthesis and signal transduction, including the majority of components in auxin signal pathway, and brassinosteroid biosynthesis and signal transduction, and some GA and ABA signal transduction genes. During seeds germination, the expression of some EXPANSIN and XYLOGLUCAN ENDOTRANSGLYCOSYLASE was also significantly enhanced. To investigate the effect of different hormone during the procedure of seed germination, the contents and the differential distribution of ABA, GA, BR and IAA in cotyledon, hypocotyl and radicle, and plumule of three seed sections at different developmental stages were also detected. Combining with previous data in other species, a model of regulatory network related to peanut seed germination was developed. This model will helpful to gain further understanding of the mechanisms controlling seed dormancy and germination.