Abstract
Phytophthora sojae, the causal agent of soybean root and stem rot, is responsible for enormous economic losses in soybean production. P. sojae secrets various effectors to reprogram host immunity. The plant apoplastic space is a major battleground in plant-pathogen interactions. Here we describe a protocol for purification and isolation of secreted proteins from P. sojae, including precipitation of secreted proteins from P. sojae culture filtrate, chromatographic purification of the secreted proteins and analysis of the proteins by Mass spectrometry. With this protocol, it will be easier to identify potential apoplastic effectors in Phytophthora and will benefit our understanding of plant-microbe interactions.