Changes in microRNAs expression of flax (Linum usitatissimum L.) planted in a cadmium-contaminated soil following the inoculation with root symbiotic fungi.

Cadmium is one of the most harmful heavy metals that harm agricultural products. Evaluating microRNAs expression is a new and accurate method to study plant response in various environmental conditions. So this study aimed to evaluate the contribution of two symbiotic fungi in improving flax tolerance in a Cd-polluted soil using microRNAs and their target gene expression. A factorial pot experiment in a completely randomized design was conducted with different levels of Cd (0, 20, and 40 mg kg−1) on non-inoculated and inoculated flax with Claroideoglomus etunicatum and Serendipita indica. The results presented that increasing Cd levels caused a constant decline of alkaline phosphatase of soil (from 243 to 210 and 153 μg PNP g−1 h−1), respectively, from control (Cd0) to 20 and 40 mg Cd kg−1. However, the inoculation of flax with fungi significantly enhanced these properties. A negative correlation was observed between the expression level of microRNA 167 and microRNA 398 with their corresponding target genes, auxin response factor 8 and superoxide dismutase zinc/copper 1, respectively. The expression level of both microRNAs and their targets indicated that the inoculation with symbiont fungi could diminish Cd stress and enhance the growth of flax. Soil contamination with Cd affects plant growth. Root symbiotic fungi can improve plant growth in Cd-polluted soils. Examining microRNA expression is a new and accurate method to evaluate plant response to Cd pollution and symbiotic fungi. Measuring microRNAs in response to fungus symbiosis and Cd pollution. Measuring proline content of flax and phosphatase enzyme activity in soil in Cd pollution and fungus inoculation treatments. [ABSTRACT FROM AUTHOR]