MicroRNAs Are Involved in Maize Immunity Against Fusarium verticillioides Ear Rot

摘要

Fusarium ear rot（FER） caused by Fusarium verticillioides is one of the most common diseases affecting maize production worldwide. FER results in severe yield losses and grain contamination with health-threatening mycotoxins. Although most studies to date have focused on comprehensive analysis of gene regulation in maize during defense responses against F. verticillioides infection, less is known about the role of micro RNAs（mi RNAs） in this process. We used deep sequencing to compare small RNA libraries from the maize kernels of susceptible（N6） or resistant（BT-1） inbred lines from uninfected plants and upon F. verticillioides infection. We found that pathogen exposure was accompanied by dynamic alterations in expression levels of multiple mi RNAs, including new members of previously annotated mi RNA families. A combination of transcriptomic, degradomic, and bioinformatics analyses revealed that F. verticillioides-responsive mi RNAs and their potential target genes displayed opposite expression patterns in the susceptible and resistant genotypes. Functional category analysis uncovered preferential enrichment of the pathogen-responsive mi RNAs and their targets in the phenylpropanoid metabolic processes,plant–pathogen interactions, and plant phytohormone signal transduction pathways. Furthermore,transgenic maize plants overexpressing mi R408 b exhibited reduced resistance to F. verticillioides infection in a susceptible maize line. These findings provide new insights into the regulatory roles of mi RNAs in maize immunity against FER and new resources for breeding disease resistance into maize.