Fusarium verticillioides- maize interaction: expression profiles of oxylipin pathway plant genes and fungal FUM genes in relation to host resistance and FB1 accumulation.

Fusarium verticillioides causes Fusarium ear rot and contaminates the grains with fumonisin mycotoxins. A quantitative genetic variation exists for resistance to Fusarium ear rot and fumonisin contamination among maize genotypes. The analysis of pathosystems has gained a new perspective from the evidence that a lipid cross-talk exists between fungus and plant, involving a group of oxygenated lipids termed oxylipins. Fungal oxylipins are known for their role in sporogenesis and mycotoxin synthesis. On the other side plant oxylipins are recognized as resistance agents against pathogen attack. This study analyzes the maize-Fusarium verticillioides pathosystem by the investigation of maize genes involved in the oxylipin production in relation to host resistance. For this reason we used a resistant (R) and a susceptible (S) maize genotype at 3, 7 and 14 days after fungal inoculation (dai). The tested genes belong to LOX class and other genes of the linoleic and linolenic acid pathways that bring to the synthesis of antimicrobial molecules, as Green Leaf Volatiles (GLVs) and Jasmonic Acid (JA). The expression of FUM genes for the fumonisin synthesis, the fumonisin kernel content and the fungal growth were tested in the same samples. Regarding the expression profile of genes involved in lipid metabolism, the two genotypes show contrasting patterns: in the R genotype the expression grows considerably between 3 and 7 dai, whereas the S line shows a mild and later response. Considering transcript values in the control samples, the R genotype demonstrates a basal expression of all genes, except for ZmLOX5 and ZmLipidBinding Protein that are highly induced after pathogen attack only in this line. The expression pattern of plant genes follows the pattern of fungal growth and mycotoxin contamination. FUM gene expression grows for both maize lines between 3 and 7 dai, but whereas the R line interrupts their transcription after 7 dai, it increases exponentially in the S genotype. Similarly, a high fumonisin content is detectable in the S line at 14 dai, whereas in the R line the contamination increases slower. Also the fungal growth, tested by the expression of a constitutive fungal gene, is reduced in the R line. So the R line is able to contain fungal growth and mycotoxin contamination by the employ of both constitutive and induced genes, that produce molecules with antimicrobial activity and regulate fungal toxicity. These results indicate that the selection of maize resistant genotypes is a useful strategy in contrasting Fusarium verticillioides damages and in preventing fumonisin contaminations in grain.