MicroRNA-Mediated Post-Transcriptional Regulation of Enzymes Involved in Herbicide Resistance in <i>Echinochloa oryzicola</i> (Vasinger) Vasinger

Herbicide resistance is an emerging phytosanitary threat, causing serious yield and economic losses. Although this phenomenon has been widely studied, only recently has the role of epigenetic factors in its occurrence been considered. In the present study, we analyzed the microRNA-mediated regulation in <i>Echinochloa oryzicola</i> (Vasinger) Vasinger (late-watergrass) of the expression of cytochromes P450, glutathione S-transferase (GST), and eIF4B, all of which are enzymes involved in profoxydim (AURA^®) detoxification. Before and after profoxydim application, the expression profiles of microRNAs (miRNAs) were selected for their ability to target the genes considered, and their targets were assessed by means of RT-qPCR. Susceptible and resistant biotypes showed different responses to this herbicide. After profoxydim application, in resistant biotypes, <i>osa-miR2099-5p</i>, <i>ath-miR396b</i>, <i>osa-miR395f</i>, <i>osa-miR396a-5p</i>, <i>osa-miR166a-5p</i>, <i>osa-miR166d-5p</i>, <i>gra-miR8759</i>, and <i>gma-miR396f</i> were not triggered, allowing the expression of CYP81A, <i>GSTF1</i>, and <i>eIF4B</i> genes and the herbicide’s detoxification. Meanwhile, the transcription of <i>ata-miR166c-5p</i>, <i>ath-miR847</i>, <i>osa-miR5538</i>, and <i>gra-miR7487c</i> was triggered, down-regulating <i>CYP71AK2</i>, <i>CYP72A254</i>, <i>CYP72A122</i>, and <i>EcGST</i> expression. In susceptible biotypes, the herbicide stimulated <i>ata-miR166c-5p</i>, <i>ath-miR847</i>, <i>osa-miR5538</i>, <i>gra-miR7487c</i>, <i>osa-miR166a-5p</i>, and <i>gra-miR8759</i>, down-regulating their respective target genes (<i>CYP72A122</i>, <i>CYP71AK2</i>, <i>EcGST</i>, <i>CYP72A254</i>, <i>CYP81A12</i>, and <i>eIF4B</i>). A better understanding of the role of miRNA-mediated epigenetic regulation in herbicide resistance will be useful in planning more targeted and sustainable methods for controlling this phytosanitary threat.