Drought responsive microRNAs in two barley cultivars differing in their level of sensitivity to drought stress

MicroRNAs (miRNAs) are known to be involved in the regulation of gene expression, including that of genes involved in the response to stress. Here, a comparison has been drawn between the miRNA profiles of a drought susceptible, 'Morocco 9-75′, and a drought tolerant, 'Yousef', barley cultivars. Leaf water content, shoot dry matter and chlorophyll content decreased in 'Morocco 9-75′ more considerably compared with 'Yousef' under drought stress. Furthermore, lower stomatal conductance and higher leaf temperature were observed in 'Morocco 9-75′ compared with 'Yousef'. Based on the criteria set for differential abundance, 118 of conserved and novel miRNAs were identified as being responsive to soil water status. Although drought stress resulted in an altered abundance of more miRNAs in 'Morocco 9-75′ than in 'Yousef', drought stress was generally associated with an increased miRNA abundance in 'Yousef' and a decreased abundance in 'Morocco 9-75'. An in silico analysis identified 645 genes as putative targets for the drought-responsive miRNAs in 'Yousef' and 3735 in 'Morocco 9-75'. Gene ontology analysis showed that drought stress was associated with the altered abundance of miRNAs targeting growth, development, the juvenile to adult transition and hormone signaling. Some miRNAs which became more abundant in 'Yousef' are thought to target genes intimately involved in development and stress adaptation. In 'Morocco 9-75′, drought stress induced changes in the abundance of miRNAs associated with genes affecting growth, development, the juvenile to adult transition and ABA signaling. The data imply that miRNAs may affect the tolerance/sensitivity of barley to drought stress by modulating the expression of a wide set of genes and induction of some physiological changes.