Transcriptome analysis of the germinated seeds identifies low-temperature responsive genes involved in germination process in Ricinus communis

Castor bean (Ricinus communis L.), an important non-edible oilseed crop, is originated in tropical regions, but is now cultivated in many subtropical areas around the world. Although it has a high economic value and is broadly used in industry, castor bean is very sensitive to low temperature, especially at the germination stage. So far, the knowledge about the mechanisms underlying the environmental effects on seed germination was largely unknown. In this study, the transcriptional profile analysis was performed in germinating castor bean seeds in response to cold stress (20 degrees C), and a total of 2411 differentially expressed genes (DEGs) were indentified in the seeds germinating at 20 degrees C in comparison with those germinating at 30 degrees C (control). The pathway enrichment analysis of DEGs showed that most of over-represented pathways were mainly related to plant secondary metabolisms. Also, most of the DEGs in the enriched pathways, including the 20 phenylpropanoids-related genes, were coordinately up-regulated in the seeds germinating at 20 degrees C, indicating that they might be key candidate genes or regulators involved in seed germination under chilling conditions. Thus, these results would give us a guide to promote the germination of crop seeds sowed in spring under low temperature.