Functional Analysis Of Cis-element Mona In Monilinia Fructicola

Peach brown rot caused by Monilinia spp. is an important disease of peach worldwide, caused serious economic losses. Monilinia fructicola is the dominant species in China. M. fructicola resulted peach brown rot in most peach growing areas of China.Currently, the management of peach brown rot mainly based on chemical control. Demethylation inhibitors(DMIs) are more effective than other types of fungicides in the control of peach brown rot, thus are widely used in the field. Resistance to DMI fungicides in M. fructicola has been found in USA but not yet in China. Based on previous studies, the DMI resistance is most likely caused by an insertion of 65 bp cis-element(Mona) at the upstream of the Mf CYP51 gene, leading to the overexpression of Mf CYP51 gene. In this study, the function of Mona was analyzed through genetic transformation experiments. Using PEG mediated transformation with the Split Marker vectors, the cis-element Mona was knocked out from resistant isolate Bmpc7 and inserted into the sensitive isolate HG12-3a. Results showed that the EC50 values and the Mf CYP51 relative expression were significantly decreased in Mona knockout transformants compared to the parental isolate Bmpc7. And the EC50 values of parental isolate Bmpc7 and knockout transformants are highly correlated with the Mf CYP51 relative expression. On the other side, as expected Mona insertion transformants showed increased EC50 values and the Mf CYP51 relative expression compared to the parental isolate HG12-3a. And the EC50 values of parental isolate HG12-3a and insert transformants are moderately correlated with the Mf CYP51 relative expression. Among both groups of transformants, the mycelia growth rate, sporulation and pathogenicity were not influenced compared to corresponding parental isolates, indicting no fitness penalty in these transformants. This study proved that the resistance to DMI fungicide was actually caused by the insertion of Mona element which can increase the overexpression of the down stream Mf CYP51 gene.