A proteomics approach to investigating promotive effects of brassinolide on lamina inclination and root growth in rice seedlings

Abstract

The application of brassinolide (BL) to the lamina joint region of rice (Oryza sativa L., cv. Nipponbare) seedlings caused marked bending of laminae, and BL influenced rice root growth under intact conditions. A remarkable increase in lamina inclination at BL 1 μM and an evident increase in root elongation at BL 0.01 μM were observed compared with the control. A total of 786 and 508 proteins extracted from the lamina joint and root, respectively, were detected in images of two-dimensional polyacrylamide gel electrophoresis with isoelectric focusing or immobilized pH gradient tube gel, and 21 proteins changed by BL treatment were analyzed using a gas-phase protein sequencer and mass spectrometer. Proteins related to photosynthesis and stress tolerance were mainly found in the lamina joint and root, respectively. Advanced degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) large subunit was caused by both BL and ethylene. Calmodulin, which decreased in roots treated with BL, increased as a result of ethephon treatment. Proteins that showed homology to glutathione S-transferase (EC 2.5.1.18) increased with BL application in both the lamina joint and root. The results suggest that the physiological functions of these proteins detected using powerful proteome analysis are implicated in rice lamina inclination and/or root elongation triggered by BL.