A spatial temporal analysis of the Fusarium graminearum transcriptome during symptomless and symptomatic wheat infection

Fusarium head blight of wheat is one of the most serious and hazardous crop diseases worldwide. Here, a transcriptomic investigation of Fusarium graminearum reveals a new model for symptomless and symptomatic wheat infection. The predicted metabolic state and secretome of F. graminearum were distinct within symptomless and symptomatic wheat tissues. Transcripts for genes involved in the biosynthesis of the mycotoxin, deoxynivalenol, plus other characterized and putative secondary metabolite clusters increased in abundance in symptomless tissue. Transcripts encoding for genes of distinct groups of putative secreted effectors increased within either symptomless or symptomatic tissue. Numerous pathogenicity-associated gene transcripts and transcripts representing PHI-base mutations that impacted on virulence increased in symptomless tissue. In contrast, hydrolytic carbohydrate-active enzyme (CAZyme) and lipase gene transcripts exhibited a different pattern of expression, resulting in elevated transcript abundance during the development of disease symptoms. Genome-wide comparisons with existing datasets confirmed that, within the wheat floral tissue, at a single time point, different phases of infection co-exist, which are spatially separated and reminiscent of both early and late infection. This study provides novel insights into the combined spatial temporal coordination of functionally characterized and hypothesized virulence strategies.