Resistant and susceptible maize genotypes activate different transcriptional responses against Fusarium verticillioides

Fusarium verticillioides is the prevailing species in maize fields producing ear rot and fumonisins that are suspected to be carcinogenic. In this study we analyze the host response in early and late stages after F. verticillioides infection in susceptible and resistant maize kernels sampled in the area neighbouring the point of inoculation. The fungal growth, assayed by qRT-PCR quantification of the tub 2 gene, was eight times lower, in average, in resistant kernels than that detected in susceptible line over the time course of 96 h. During the very early stages of infection (12e24 h after infection) a small proportion of the host transcripts was induced. The number of differentially regulated genes reached 147 at 48 h after infection and decreased to 140 and 98 at 72 and 96 h post infection, respectively. About 1.0% of the genes assayed were differentially expressed and 7.1% of them was assigned to the category cell rescue, defense and virulence. Pathogenesis-related protein-5, endo-1,3e1,4-beta-D-glucanase PRm6, chitinase PRm3 and MYB-like DNA binding protein had a higher level of expression in the resistant line compared to the susceptible one. Since having analyzed the area around the point of infection, the resistant line may activate more efficiently a battery of defense genes, before the invasion by the fungus in non damaged tissues or in adjacent ones. These outcomes indicate that the resistant kernels activated a basal defense programme where the expression of defense genes is controlled by both the host genotype and induced by the pathogen.