Proteomic analysis of Physcomitrella patens treated with 12-oxo-phytodienoic acid, an important oxylipin in plants.

12-Oxo-phytodienoic acid (OPDA) is biosynthesized in the octadecanoid pathway and is considered to be a signaling molecule in plants. In Physcomitrella patens, OPDA is induced by bacterial infection and mechanical stress and is known to suppress growth; however, the functional mechanism of OPDA signaling remains elusive. In this study, we performed a proteomic analysis of P. patens treated with OPDA and found that the expression of 82 proteins was significantly altered, with approximately 80% of these proteins being downregulated by OPDA. The identified proteins were mainly categorized as being involved in photosynthesis, metabolism, and protein synthesis, and most of the proteins that were upregulated by OPDA are involved in light-dependent reactions, suggesting that OPDA regulates a function in chloroplasts. Additionally, OPDA induced the expression of an allene oxide cyclase (PpAOC1) in the octadecanoid pathway, demonstrating positive feedback regulation by OPDA in P. patens.