Abstract: To understand the molecular mechanism of rice (Oryza sativa L.) in response to methylmercury (MeHg) stress, we analyzed the expressed proteins in root tips of rice Liangyou 302 under MeHg stress using isobaric tags for relative and absolute quantitation (iTRAQ) and liquid chromatographytandem mass spectrometry (LC-MS/MS). Differential proteins were elucidated in view of bioinformatics and molecular biology. The results showed that a total of 3508 proteins were quantified in both the control and MeHg treatment. According to fold change (≥1.20 or ≤0.83) andP<0.05, a total of 88 differentially expressed proteins were identified, out of which 32 proteins were upregulated and 56 proteins were down-regulated. There were 15 differentiallyexpressed proteins associated with the characteristic of metal ion binding, including 12 knownproteins of germination like proteins, lipoxygenase, and three unknown proteins. Results from the molecular functions of gene ontology (GO) suggested that differentially expressed proteins were mainly involved in catalytic activity, binding and transport activity, while the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway exhibited that they were significantly enriched in protein processing in endoplasmic reticulum, oxidative phosphorylation, starch and sucrose metabolism, and phenylpropanoid biosynthesis. Our results provide insight into regulating absorption of MeHg in rice.

Key words: urban river survey, stretch scale, stretch habitat quality index, Taihu Lake Basin, iTRAQ, methylmercury stress, differentially expressed protein, rice.