Expression profile of miRNAs in Populus cathayana L. and Salix matsudana Koidz under salt stress.

Soil salinization can lead to environmental and ecological problems worldwide. Abiotic stressors, including salinity, are suspected to regulate microRNA (miRNA) expression. Plants exposed to such abiotic stressors express specific miRNAs, which are genes encoding small non-coding RNAs of 20-24 nucleotides. miRNAs are known to exist widely in plant genomes, and are endogenous. A previous study used miRNA microarray technology and poly(A) polymerase-mediated qRT-PCR technology to analyze the expression profile of miRNAs in two types of plants, Populus cathayana L. (salt-sensitive plants) and Salix matsudana Koidz (highly salinity-tolerant plants), both belonging to the Salicaceae family. miRNA microarray hybridization revealed changes in expression of 161 miRNAs P. cathayana and 32 miRNAs in S. matsudana under salt stress. Differences in expression indicate that the same miRNA has different expression patterns in salt-sensitive plants and salt-tolerant plants under salt stress. These indicate that changes in expression of miRNAs might function as a response to varying salt concentrations. To examine this, we used qRT-PCR to select five miRNA family target genes involved in plant responses to salt stress. Upon saline treatment, the expressions of both ptc-miR474c and ptc-miR398b in P. cathayana were down-regulated, but were up-regulated in S. matsudana. Expression of the miR396 family in both types of plants was suppressed. Furthermore, we have analyzed the different expression patterns between P. cathayana and S. matsudana. Findings of this study can be utilized in future investigations of post-transcriptional gene regulation in P. cathayana and S. matsudana under saline stress.