Regulatory roles of introns in fungicide sensitivity of Fusarium graminearum.

Although the roles of introns have been much debated in eukaryotic organisms, none of them have been functionally characterized in Fusarium graminearum. In this study, we characterized the roles of introns in regulation of fungicide-sensitivity of F. graminearum. β2 tub, cyp51A and myosin-5 are important target genes of benzimidazoles, triazoles and cyanoacrylates respectively. To explore the sensitivity regulation functions of introns in target genes, several detailed deletion studies were completed on the intronic regions of β2 tub, cyp51A and myosin-5. Phenotypic analyses showed that deletion of the fourth intron from β2 tub gene (designated β2 Δi4), the sole intron from cyp51A gene (cyp51A-Δi) and the second intron from myosin-5 gene (myo5-Δi2) exhibited an increased sensitivity to corresponding fungicides. In contrast, deletion of the first or second intron from β2 tub gene exhibited a decreased sensitivity to carbendazim. qRT-PCR showed that the mRNA transcript levels of target genes were significantly downregulated in β2 Δi4, cyp51A-Δi and myo5-Δi2 respectively. Meanwhile, Western blot assays revealed that the protein expression levels of β2 tub was also dramatically reduced in β2 Δi4, but accumulated in β2 Δi1 and β2 Δi2. Overall, our results indicate that introns in target genes significantly regulate the fungicide-sensitivity by influencing expression of the corresponding resident genes in F. graminearum.