Micro-RNA Regulation for Boron Toxicity Tolerance in Barley

Micro-RNAs (miRNA) are small, endogeneuos and regula- tory RNAs playing important roles in plant development and stress responses. Boron toxicity is one of the important abiotic stress factors for plant growth and development. Barley (Hordeum vulgare) is a mainly produced crop plant for human nutrition and animal feeding. To investigate the regulatory roles of miRNAs for boron toxicity tolerance in barley a comperative approach is applied for naturally boron tolerant model barley (Sahara). On the other hand limited number of barley miRNAs have been identified to date. Excess amount of boron treated barley leaf and root samples were used for Illumina Solexa deep sequencing (miRNA identification) and degradome (miRNA-target gene discov- ery) sequencing. Comparative expression analyzes showed that many of the miRNAs are differentially expressed upon excess boron treatment in tissue specific manner. Target gene expressions were measured as correlated with miRNA expression upon toxic level of boron treatment. GO and KEGG analyzes for target genes have shown few pathways take roles in boron toxicity tolerans in root and leaf tissues. Quantitative RT PCR (qRT-PCR) measurements validate our miRNA and target gene expression results in boron treated barley tissues. Additionally, the genes known as playing roles in boron uptake, export and tolerans mecha- nisms were searched to find out their specific regulatory miRNAs via bioinformatic analyzes.