Seed is the most basic and important material in agriculture, good seed germination is the prerequisite for good seeding. Seed germination is a well-regulated process involving a number of coordinated signal transduction events. Protein phosphorylation is intimately involved in regulating the germinating process. To date, however, no systemic studies have examined the phosphoproteomics of rice seed germination. 

Scientists in Key Laboratory of Plant Germplasm Enhancement and Speciality Agriculture from Wuhan Botanical Garden (WBG) collaborated with Professor Setsuko Komatsu’ research team from National Institute of Crop Science (Japan) used gel-free proteomics techniques to study the dynamic changes of protein and phosphoprotein abundance in embryos during rice seed germination.

The analyses of whole proteomic data and protein-protein interactions indicated that the regulation of sucrose synthases and alpha-amylases was the central event controlling germination. Phosphoproteomic analysis revealed that the majority of differentially phosphorylated proteins were involved in protein modification and transcriptional regulation. Cluster analysis indicated that 12 protein modification-related proteins had a peak 24 abundance of phosphoproteins at 12 h after imbibitions.

These results suggest that the first 12 h following imbibition is a potentially important signal transduction phase for the initiation of rice seed germination. Three core components involved in brassinosteroid (BR) signal transduction displayed significant increases in phosphoprotein abundance during the early stages of germination. Brassinolide treatment increased the rice seed germination rate but not the rate of embryonic axis elongation. These findings suggest that brassinosteroid signal transduction likely triggers seed germination.

This work was supported by the National Natural Science Foundation of China, and results were published in Journal of Proteome Research entitled “Quantitative Proteomics Reveals the Role of Protein Phosphorylation in Rice Embryos during Early Stages of Germination”.

Cluster analysis of significantly changed phosphoproteins in rice embryos during germination (Image by WBG)