A Novel Maize MicroRNA Negatively Regulates the Resistance to Fusarium
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.