Barley miRNAs and their targets regulation in response to heat stress at the early stage of development

MiRNAs are key regulators of gene expression controlling plant development and response to environmental stresses. In this work we studied global dynamics of accumulation of conserved and identified novel barley miRNAs at early stage of plant development during heat stress (1h, 3h and 6h of heat stress). The majority of miRNAs responds to heat stress after 3h and 6h of heat stress duration (124 and 155, respectively). The comparison of heat-induced changes in mature miRNA accumulation to their cognate precursor levels allowed to indicate a smaller group of miRNAs that are controlled at transcriptional level and a larger group that is controlled posttranscriptionally in response to heat stress. For miRNAs with the significant accumulation changes during heat treatment, target mRNAs were identified. Moreover, novel targets have been experimentally assigned for selected miRNAs. mRNA of the effector protein of miRNA activity, AGO1B was found to be downregulated by increased miR168 during heat stress. Importantly, miRNA/mRNA target module miR399c/PHO2 responsible for the phosphorus uptake exhibits dynamic changes under heat stress conditions suggesting adaptation of plant development to stress conditions. This study provides new data for developing miRNA and their mRNA target-based strategies in barley breeding in response to heat stress. Keypoints- Involvement of small RNAs in response to the heat stress conditions have been studied in young barley plants. - The largest number of heat responsive miRNAs was found after 3h and 6h of heat duration. - Heat-induced mature miRNA accumulation and their precursor levels showed complex transcriptional or posttranscriptional regulation. - MiRNA-target modules responsive to heat stress were identified