Proteomic analysis of secreted proteins from aseptically grown rice

T. Shinano, , , S. Komatsu, T. Yoshimura, S. Tokutake, F.-J. Kong, T. Watanabe, J. Wasaki and M. Osaki

 

Phytochemistry, 72, 312-320 (2010)

Abstract

Plants are known to secrete a variety of compounds into the rhizosphere. These compounds are thought to play important roles in the regulation of soil chemical properties and soil microorganisms. To determine the composition of proteins secreted from rice roots, aseptic hydro culture was performed, and the collected proteins were analyzed. Over 100 proteins were identified; most were identified using the rice database (RAP-DB), and about 60% of the identified proteins were suspected to have a signal peptide. Functional categorization suggested that most were secondary metabolism- and defense-related proteins. Pathogenesis- and stress-related proteins were the major proteins found in the bathing solution under aseptic conditions. Thus, we propose that rice plants constitutively secrete a large variety of proteins to protect their roots against abiotic and/or biotic stresses in the environment. Graphical abstract To investigate proteins secreted from rice roots, rice plants were grown aseptically in an hydroculture system. Nano-LC–MS/MS analysis indicated that a large number of identified proteins belong to defense related proteins.

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Highlights ► Secreted proteins were collected from root bathing solution of rice. ► Nano-LC–MS/MS succeeded to identify over 100 proteins. ► PR-proteins are constitutively secreted under aseptic conditions.

Keywords: Rice; Oryza sativa; Gramineae; Aseptically growth; Hydroponic culture; Proteome; Root; Secreted proteins; Plants Abbreviations: BPB, bromophenol blue; CHAPS, 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate; DTT, dithiothreitol; IPG, immobilized pH gradient; IEF, isoelectric focusing; LC–MS/MS, liquid chromatography–tandem mass spectrometry; MALDI-TOF-MS, matrix-assisted laser desorption ionization time-of-flight mass spectrometry; PAP-H, pokeweed antiviral protein; PR, pathogenesis related; RAP-DB, rice annotation project database; RIPs, ribosome-inactivating proteins; SCD, soybean casein digest