Study on nucleic acid metabolic pathways during early seed development to improve rice grain quality

초록

Understanding the molecular mechanisms underlying early seed development is important for improving grain yield and quality in crop plants. To investigate the molecular mechanisms that occur during early seed development, we performed comparative label-free quantitative proteomic analysis on developing rice seeds between 0 and 1 day after pollination (DAP). A total of 5231 proteins were identified, and 902 proteins showed differential accumulation between 0 and 1 DAP seeds. Further analysis focused on the proteins preferentially expressed at 1 DAP and revealed an enrichment of proteins involved in DNA replication and pyrimidine biosynthetic pathways. In particular, the cytidine triphosphate synthase OsCTPS1, which has been reported to play an essential role in endosperm development, was found to accumulate specifically at 1 DAP. CTPS serves as the rate-limiting enzyme of cytosine nucleotide biosynthesis. Mutations in the OsCTPS1 resulted in an endospermless phenotype and an enlarged embryo. Conversely, OsCTPS1-overexpressing plants exhibited increased seed size, weight, and levels of the neurotransmitter gamma-aminobutyric acid (GABA). Treatment of protoplasts from transgenic plants overexpressing OsCTPS1-GFP with various signaling inhibitors revealed that inhibition of phosphorylation increased the stability of the protein. In this study, we tried to understand the molecular mechanisms of early seed development at the post-transcriptional regulation. Based on regulatory mechanisms that control OsCTPS1 protein stability, we expect to improve quantity and quality of seed with genome editing technology.