Carbonylated protein changes between active germinated embryos and quiescent embryos give insights into rice seed germination regulation

Rice seed germination is the determining physiological event during establishment of a new plant. Although numerous researches have focused on this complicated process, studies that disclose the carbonylated protein differences between active and quiescent rice embryos related with seed germination remain deficient. Here, protein carbonylation in rice seed embryo has been analyzed by two-dimensional electrophoresis (2-DE), anti-2,4-dinitrophenyl (DNP) immunoassay, and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) methods. As expected, varieties of carbonylated proteins were observed to increase along with rice seed germination. Certain proteins like catalase, IAA-amino acid hydrolase, cell structural proteins, and 26S protease regulatory subunit were specifically carbonylated in 48 h embryos. We speculate that ROS directly participate in cell wall loosening, cell expansion, and radicle elongation, which are facilitated by the carbonylation damage of antioxidant enzyme catalase upon imbibition. Carbonylation degradation of IAA conjugates hydrolase and cell structural proteins were necessary for hormone regulation and materials providing in seedling establishment. We also provided evidence that Dnak-type molecular chaperone hsp70, enzymes involved in glycolysis pathway, and actins were always carbonylated in 0 and 48 h embryos. Of note, glycolytic enzymes were the most prominent carbonylated proteins. Furthermore, embryo specific cupin family proteins were intensively carbonylated in 0 h embryos thus helping in reserves mobilization to facilitate germination. These results indicate that protein carbonylation in seed embryo proteins do not occur randomly, and ROS directly or indirectly participate in rice seed dormancy breakage and seedling establishment.