A Novel Maize MicroRNA Negatively Regulates the Resistance to Fusarium Verticillioides

Despite miRNAs regulate the defense response against multiple pathogenic fungi in diverse plant species, few efforts had been devoted to deciphering the involvement of miRNA in resistance to Fusarium verticillioides ( F. verticillioides ), a major pathogenic fungal in maize production. In this study, we discovered a novel F. verticillioides- responsive miRNA designated zma-unmiR4 in maize kernels. The expression levels of zma-unmiR4 were significantly repressed in the resistant maize line but induced in the susceptible lines upon F. verticillioides exposure, whereas its target gene ZmGA2ox4 exhibited the opposite pattern of expression. Heterologous overexpression of zma-unmiR4 in Arabidopsis resulted in enhanced growth and compromised resistance to F. verticillioides . By contrast, transgenic plants overexpressing ZmGA2ox4 or the homolog AtGA2ox7 showed impaired growth and enhanced resistance to F. verticillioides . Moreover, zma-unmiR4-mediated suppression of AtGA2ox7 disturbed the accumulation of bioactive gibberellin (GA) in transgenic plants and perturbed a set of defense-related genes in response to F. verticillioides . Exogenous application of GA or GA biosynthetic inhibitor could modulate F. verticillioides resistance in different plants . Taken together, our results suggest that zma-unmiR4- ZmGA2ox4 module might act as a major player in balancing growth and the resistance to F. verticillioides pathogen in maize.