Barley primary microRNA expression pattern is affected by soil water availability.

MicroRNAs are short molecules of 21-24 nt length. Present in all eukaryotic organisms, they regulate gene expression by guiding posttranscriptional silencing of mRNAs. In plants, they are key players in signal transduction, growth and development, and response to abiotic and biotic stresses. Barley ( Hordeum vulgare ) is an economically important monocotyledonous crop plant. Drought is the world’s main cause of loss in cereal production. We have constructed a high-throughput Real-Time RT-qPCR platform for parallel determination of 159 barley primary microRNAs levels. The platform was tested in two drought-and-rehydration-treated barley genotypes (Rolap and Sebastian). We have determined changes in the expression of primary microRNAs responding to mild drought, severe drought, and rehydration. From the results, we conclude that the primary microRNA expression is altered relative to the stress intensity. Mild drought and rehydration mostly decrease the pri-miRNAs levels in both of the tested genotypes. Severe drought mainly induces primary microRNA expression. The main difference between the genotypes tested was a much-stronger induction of pri-miRNAs in Rolap encountering severe drought. The primary microRNAs respond dynamically to mild drought, severe drought, and rehydration treatments. We propose some of the individual pri-miRNAs to be drought stress or rehydration markers. We recommend the primary microRNA RT-qPCR-based platform to be a universal tool for testing the strength of drought response in barley. Hence, the platform can be used to determine drought stress levels applied to barley plants. The usage of the platform in biotechnology is also postulated.