A proteomic analysis of wheat defense response induced by the widely used organophosphorus nematicide fosthiazate is reported.Seed germination and two-dimensional gel electrophoresis (2-DE) experiments were performed using a Chinese wheat cultivar,Zhenmai No.5.Root and shoot elongation decreased but thiobarbituric acid reactive substances (TBARS) content in embryos increased with increasing pesticide concentration.More than 1000 protein spots were reproducibly detected in each silver-stained gel.Thirty-seven protein spots with at least 2-fold changes were identified using MALDI-TOF MS/MS analysis.Of these,24 spots were up-regulated and 13 were down-regulated.Proteins identified included some well-known classical stress responsive proteins under abiotic or biotic stresses as well as some unusual responsive proteins.Ten responsive proteins were reported for the first time at the proteomic level,including fatty acyl CoA reductase,dihydrodipicolinate synthase,DEAD-box ATPase-RNA-helicase,fimbriata-like protein,waxy B1,rust resistance kinase Lrl0,putative In2.1 protein,retinoblastoma-related protein 1,pollen allergen-like protein and S-adenosyl-Lmethionine:phosphoethanolamine N-methyltransferase.The proteins identified were involved in several processes such as metabolism,defense/detoxification,cell structure/cell growth,signal transduction/transcription,photosynthesis and energy.Seven candidate proteins were further analyzed at the mRNA level by RT-PCR to compare transcript and protein accumulation patterns,revealing that not all the genes were correlated well with the protein level.Identification of these responsive proteins may provide new insight into the molecular basis of the fosthiazate-stress response in the early developmental stages of plants and may be useful in stress monitoring or stress-tolerant crop breeding for environmentally friendly agricultural production.