Fusarium verticillioides FUM1 and FUM19 gene expression in maize kernels during early infection

摘要

Fusarium verticillioides is the causal agent of Fusarium ear rot (FER), an economically important disease of maize worldwide. The fungus also produces fumonisins in maize grain, which poses a food safety concern. To better understand the molecular interactions between maize and F. verticillioides during infection, genes expressed in infected and healthy maize kernels have been investigated. The expression of fungal genes in grain during infection has, however, received little attention. This is because fungal RNA forms only a fraction of the total RNA present in maize kernels, making transcriptome sequencing thereof difficult. The aim of this study, thus, was to study the expression of two F. verticillioides fumonisin biosynthetic (FUM) genes in maize kernels by reverse-transcription quantitative PCR (RT-qPCR). The ears of a susceptible maize inbred line were artificially inoculated with F. verticillioides, and maize kernels harvested 0, 7 and 14 days after inoculation (dai). The relative expression of the FUM1 and FUM19 genes was then quantified using RT-qPCR, and correlated to fumonisin levels in the kernels. Both genes were up-regulated in the fungus-inoculated plants 7 dpi, when fumonisin levels and F. verticillioides DNA concentration in the infected kernels increased. After 14 days with increasing fumonisin levels, the relative expression of FUM1 was further increased, but not that of FUM19. There was no significant correlation between in planta FUM gene expression and fumonisin concentration in maize kernels (P > 0.05). The optimization of a RT-qPCR protocol has provided a targeted approach to study fungal genes that play a role in pathogenesis and fumonisin production in planta and can further provide insights into the F. verticillioides-maize pathosystem.