ABSTRACT: BACKGROUND:Arbuscular mycorrhizal (AM) fungi form symbiotic associations with host plants can protect host plants against diverse biotic and abiotic stresses, and promote biodegradation of various contaminants. However, the molecular mechanisms of how the arbuscular mycorrhizal fungi and host plant association on atrazine stress were still poorly understood. To better characterize how arbuscular mycorrhizal fungi and host plant interactions increase atrazine stress, we performed physiological and proteomic analysis of Funneliformis mosseae (mycorrhizal fungi) and Medicago sativa (alfalfa) association under atrazine stress. RESULTS:The results showed that in the Arbuscular mycorrhizal, protective enzymes were up regulated and the malondialdehyde content increased relative to those of non-mycorrhizal M.sativa. We also examined the atrazine degradation rates within the nutrient solution, and a 44.43% reduction was observed with the mycorrhizal M.sativa, with 30.83% of the reduction attributed to F. mosseae. The accumulation content in root and stem of mycorrhizal M.sativa were obviously increased 11.89% and 16.33% than those of non- mycorrhizal M.sativa. The activity of PPO, POD, CAT and SOD in mycorrhizal M.sativa were obviously higher than non mycorrhizal M.sativa under atrazine stess. We identified differential root proteins using isobaric tags for relative and absolute quantization coupled with liquid chromatography-mass spectrometry, with 533 proteins identified (276 unregulated and 257 downregulated). The differentially expressed proteins were further examined using GO, BLAST comparisons, and a literature inquiry and were classified into the categories of atrazine degradation (37.1%); atrazine stress response (28.6%); plant immune responses (14.3%); translation, synthesis, and processing (10%); and signal transduction and biological processes (10%). Furthermore, we identified glycosyl transferase, glutathione S-transferase, laccase, cytochrome P450 monooxygenase, peroxidase, and other proteins closely related to the degradation process. CONCLUSIONS:Mycorrhizal Medicago showed improved atrazine degradation within the culturing medium and increased atrazine enrichment in the roots and stems. Additionally, AMF increased the plant root response to atrazine, with relevant enzymes up regulated and toxic effects alleviated. Overall, the findings of this study show that AMF played an important role in easing atrazine stress in plants and contributed to atrazine remediation and further contributed to the understanding of the molecular mechanism associated with atrazine stresses and potential mycorrhizal contributions in M.sativa.
