Abstract
Plants possess defense mechanisms to protect themselves from pathogen attack. Previously, we showed that OsRac1, a small GTPase Rac homolog of rice, plays a general role in disease resistance of rice. In this study, to identify effectors that interact with OsRac1 during defense responses, we carried out affinity chromatography of OsRac1 and mass spectrometric analyses of isolated proteins. Using GST-OsRac1 affinity columns, we purified several OsRac1 effectors from the cytosolic fractions of rice cells. The peptide sequences of these effectors were determined by liquid chromatography-coupled tandem mass spectrometry (LC-MS/MS). The identified proteins include NBS domain-containing proteins, which are homologs of disease resistance genes. Other identified proteins are a protein kinase and a scaffold protein OsRWD, receptor for activated C-kinase 1 (RACK1) homolog. Using yeast two-hybrid assays, we confirmed direct interactions of these candidate proteins with OsRac1.
