Potassium (K) deficiency in soil has become a global problem in agricultural production, seriously restricting crop production and agricultural sustainable development. Identification of the microRNAs associated with K use efficiency and understanding their functions in response to low K stress will be helpful for developing crop varieties with low K tolerance. Our previous study identified a low K tolerant accession, XZ153 from Tibetan wild barley. In this study, small RNA and degradome analysis were performed on two barley genotypes differing in low K tolerance (XZ153, tolerant; ZD9, sensitive) to identify the miRNAs and their targets responding to low K stress. A total of 1108 miRNAs were detected in shoots of XZ153, and ZD9 at 2 d and 7 d after low K stress, and their targets were identified through bioinformatics prediction and degradome analysis. Totally 65 differentially expressed miRNAs responding to low K stress were identified. The results showed that miR164c, miR169 h and miR395a modules could mediate TCA cycle, glycolysis pathway and pentose phosphate pathway responding to low K stress. The osa-miR166g-3p and ghr-miR482b may act as the regulators in Ca2+ signaling pathway in response to low K stress. The methionine salvage cycle involved in ethylene biosynthesis process, mediated by miR396c-3p and osa-miR171e-5p, might be also involved in responding to low K stress. Some miRNAs, including miR160a, miR396c and miR169 h, which participated in photosynthesis regulation under low K stress, differed between the two barley genotypes. In conclusion, these exclusively expressed miRNAs and their targets might play the crucial roles in low K tolerance.
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