Defense Responses to Mycotoxin-Producing Fungi Fusarium proliferatum, F. subglutinans, and Aspergillus flavus in Kernels of Susceptible and Resistant Maize Genotypes

Abstract

Developing kernels of resistant and susceptible maize genotypes were inoculated with Fusarium proliferatum, F. subglutinans, and Aspergillus flavus. Selected defense systems were investigated using real-time reverse transcription-polymerase chain reaction to monitor the expression of pathogenesis-related (PR) genes (PR1, PR5, PRm3, PRm6) and genes protective from oxidative stress (peroxidase, catalase, superoxide dismutase and ascorbate peroxidase) at 72 h postinoculation. The study was also extended to the analysis of the ascorbate-glutathione cycle and catalase, superoxide dismutase, and cytosolic and wall peroxidases enzymes. Furthermore, the hydrogen peroxide and malondialdehyde contents were studied to evaluate the oxidation level. Higher gene expression and enzymatic activities were observed in uninoculated kernels of resistant line, conferring a major readiness to the pathogen attack. Moreover expression values of PR genes remained higher in the resistant line after inoculation, demonstrating a potentiated response to the pathogen invasions. In contrast, reactive oxygen species-scavenging genes were strongly induced in the susceptible line only after pathogen inoculation, although their enzymatic activity was higher in the resistant line. Our data provide an important basis for further investigation of defense gene functions in developing kernels in order to improve resistance to fungal pathogens. Maize genotypes with overexpressed resistance traits could be profitably utilized in breeding programs focused on resistance to pathogens and grain safety.

Resistance to Fusarium verticillioides and fumonisin accumulation in maize inbred lines involves an earlier and enhanced expression of lipoxygenase (LOX) genes

“…Cultures and conidia were prepared as described in Lanubile et al (2015), obtaining a final concentration of spore suspension of 3.5 × 10 6 conidia/ml. Maize ears were inoculated at 15 days after hand-pollination using a side-needle inoculator, already described in Lanubile et al (2015).…”

“…Cultures and conidia were prepared as described in Lanubile et al (2015), obtaining a final concentration of spore suspension of 3.5 × 10 6 conidia/ml. Maize ears were inoculated at 15 days after hand-pollination using a side-needle inoculator, already described in Lanubile et al (2015). For the detection of fungal strain, gene expression analyses and fumonisin content, the inoculated and immediately adjacent kernels were collected at 3, 7, 14 and 21 days post inoculation (dpi).…”

“…Total RNA extraction and purification were performed according to Lanubile et al (2015). Real-time RT-PCR experiments were performed on kernels collected at 3, 7 and 14 dpi using the 2× iQ SYBR Green Supermix (Bio-Rad, Hercules, CA, USA) and the CFX-96 device (Bio-Rad).…”

Infection with toxigenic and atoxigenic strains of Aspergillus flavus induces different transcriptional signatures in maize kernels

“…Maize ears were inoculated 15 days after hand-pollination using a side-needle inoculator, as reported by Lanubile et al (2015). The inoculated and immediately adjacent kernels were collected at 24, 48, 72 and 96 h post-inoculation (hpi).…”

“…Total RNA extraction and purification were performed according to Lanubile et al (2015). Real-time RT-PCR experiments were performed on kernels collected at 24, 48, 72 and 96 hpi using the 2x iQ SYBR Green Supermix (Bio-Rad, Hercules, CA, USA) and the CFX-96 device (Bio-Rad).…”