Identification of endogenous peptides in maize

The extraction and identification of endogenous peptides from plants are relatively unexplored because of the degradation of peptides after extraction from plant tissues. In this study, we developed an optimized sample preparation protocol that combined constant water heating with plant protease inhibitors and TCA-acetone precipitation, resulting in the effective extraction of endogenous peptide from plants, such as maize, while diminishing unspecific protease activity. The results showed that a total of 2867 endogenous peptides were identified in three maize samples using this method, of which 2119 (73.9%) peptides were commonly identified in all three samples. The length and molecular weight of these peptides ranged from 8 to 25 amino acids and from 729.44 to 2980.62 Da, respectively, with 96.4% of the peptide scores greater than 40. These results indicated that our extraction method is highly reproducible, precise, and wide-ranging, providing optimized information for large-scale identification of plant endogenous peptides.