Analysis Of Alfalfa Mycorrhizal Transcripts Under Atrazine Stress

More than 80% of land plants form chimeric organ called mycorrhizae with AMF(arbuscular mycorrhizal fungi). AMF significantly extend the volume of soil to which the host plant root can access, thus provide better nutrient uptake, improve plant growth and alleviate toxicity of pollutants. Many excellent features of plant have been given by AMF, such as better nutrition supply and able to overcome biological/ abiotic stresses. The AMF in this paper has been selected by Funneliformis mosseae(F. mosseae), which widely distributed and as the dominant species in soil microbial communities in Northeast of China. Through the pre-test verification, we can conclude that F. mosseae has a good feature of atrazine degradation.The host plant has been selected by Medicago sativa in this paper, which sensitive to atrazine. With the assistance of AMF, it can grow normally in atrazine environment and exclude the interference of plant absorption. At the same time, M. sativa is close relative with Medicago truncatula, a model organism, which provides the molecular basis for atrazine degradation.By using the three compartments culture system and transcriptome sequencing technology, we have researched differentially expressed genes in the process of forming arbuscular mycorrhizal between M. sativa and F. mosseae under atrazine stress. The result shows M. stavia and F. mosseae can grow normally in three compartments culture system, infection rate can reach 80% under the stress of atrazine, the maximum degradation rate in side compartment can attain to 74.65%(including natural degradation) in soil. We selected the best group to conducting transcriptome sequencing depended on degradation rate and infection rate. 33948 genes were obtained by transcriptome sequencing. 2060 differentially expressed genes come from different compartment, of which 172 genes were up-regulated and have significantly difference. We divide these genes into 7 categories depended on respective functions, which are molecular processes/other proteins, zinc finger proteins, intracellular or extracellular enzymes, structural proteins, anti-stress/anti-disease protein, electron transport-related proteins and plant growth associated proteins. On the one hand, mycorrhiza improves the resistance of M. sativa under the stress of atrazine; on the other hand, increased expression of laccase and glutathione peroxidase can decompose the atrazine in soil. This study shows the high efficiency of atrazine degradation in plant-fungus mycorrhizal association and provides insights to the molecular mechanisms involved. The results of soil enzyme activities coincided well with extracellular enzymes results of transcriptome sequencing data, which further verified the accuracy of this design. The RT-PCR experiment results of 10 selected genes had similar expression level with transcriptome sequencing data, which has excluded the possibility of false positive data.