Preliminary identification of the changes of physiological characteristics and transcripts in rice after-ripened seeds

A common way of breaking seed dormancy in cereal crops is by treating seeds with a period of dry storage or after-ripening. In this study, we determined changes in the physiological characteristics and transcripts in after-ripened seeds in rice. Phenotypic data showed that the seed dormancy of five rice varieties was gradually released with after-ripening. Physiological results showed that, at the early stage of after-ripening from the freshly harvested seeds (0 days after-ripening, DAR) to 28 DAR, abscisic acid (ABA) content significantly decreased, hydrogen peroxide (H₂O₂) levels significantly increased, superoxide dismutase (SOD) and α-amylase activities significantly raised, and bioactive gibberellin (GA₁) content and ascorbate peroxidase (APX) activity showed no changes in Nipponbare seeds. RNA-seq showed that the 149 changed transcripts were observed at the early stage of after-ripening. Of these transcripts, transcript levels of OsOxO1, OsNCED4, RSOsPR10, and OsPR10a mainly occurred at early stages by the verification of four other rice varieties in after-ripened seeds, perhaps signifying that those transcripts played pivotal roles in rice after-ripening. At the late stage of after-ripening, from 28 to 56 DAR, there were merely changes in transcription and translation. Our results facilitated an understanding of the biological process of after-ripening and dormancy release in rice seeds.