Physiological Responses And Mirna Expression Dynamics Of Populus Euphratica Under Saline Stress

Populus euphratica Oliv. is a unique tree species widely distributed in North-west China, for the outstanding abilities of drought and salt resistance, it can survive in the harsh environment and contributed for maintaining the ecological balance of the desert area, meanwhile the euphratica poplar is also a model tree specie for the reaseach of plant stress-resistence especially salt-resistence mechanisms. miRNA is a small non-coding RNA, regulated in post-transcription level though binding to mRNA to inhibit or degrade the target. In this experiment we used clones of P. euphratica as material to study the change of physiological indexs, then sequenced the leaves and roots samples at different time points to find salt-response miRNA, to investigate the expression differences between organs and time. We used multivariate normal distribution based model to cluster dynamic expressed miRNA, then predicted and annotated its’target gene. The role of miRNA in salt stress responsed P. euphratica was discussed. We obtained the following results:(1) Na+concentrations, SOD activities and ABA contents rised after300mmol NaCl treatment, the physiological indexs changed significantly at6h, but K+concentrations, MDA, chlorophyll a, b and carotenoid contents remained steadily. The result indicated P. euphratica had a quickly and efficiently physiological response for salt stress.(2) After analized sequencing result, we found290conserved miRNA,75of which were leaf-specific high expressed,86were root-specific high expressed, the mainly regulated targets were transcription factors. miRNA expressions have been significantly changed at different time points as salt stressed, numbers of up-regulated miRNA varied from11to117, numbers of down-regulated miRNA varied from23to169. After annotated some high expressed miRNA, we found the miRNAs’target gene were transcription factors, hormone response factors and ATPases et al. Then we predicted some novel-miRNAs by software, obtained45novel miRNA candidates.(3) We used multivariate normal distribution based model to cluster dynamic expressed miRNA, the result showed cluster number of miRNA counts from4to13clusters, then we tested the significance of gene-enviroment interaction and annotated the miRNA, the miRNA annotations of some clusters were mainly related to response to environmental stimulus and cell death.For the first time we used clones of P. euphratica as matearials for miRNA reserch, which can avoid interferences come from samples’different genetic background. Timescale of experiment including short-term shock phase and long-term adaption phase, which can reflect the physiological and miRNA expression changes in entire time couse. We then used advanced statistic model to cluster genes. This result will benifit further reserch for plant salt-resistence mechanisms.