Evidence for the role of CYP51A and xenobiotic detoxification in differential sensitivity to azole fungicides in boxwood blight pathogens

Authors: STRAVORAVDIS, STEFANOS - University Of Massachusetts; Leblanc, Nicholas; MARRA, ROBERT - Connecticut Agricultural Experiment Station; Crouch, Jo Anne; HULVEY, JONATHAN - Eastern Connecticut State University

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2021
Publication Date: 8/26/2021
Citation: Stravoravdis, S., Leblanc, N.R., Marra, R.E., Crouch, J.A., Hulvey, J.P. 2021. Evidence for the role of CYP51A and xenobiotic detoxification in differential sensitivity to azole fungicides in boxwood blight pathogens. International Journal of Molecular Sciences. 22:9255. https://doi.org/10.3390/ijms22179255
DOI: https://doi.org/10.3390/ijms22179255

Interpretive Summary: To reduce losses due to boxwood blight disease, growers use several fungicides. One of the two fungi that cause boxwood blight, Calonectria henricotiae, is less sensitive to fungicides than the second species that causes the disease, Calonectria pseudonaviculata. This research investigated whether genes are expressed differently by the two boxwood blight fungi when they are exposed to fungicides. Results showed that gene expression by 17 detoxification genes was increased due to fungicide treatments. In addition, 25 xenobiotic detoxification genes were over expressed in Calonectria henricotiae relative to the fungicide-sensitive Calonectria pseudonaviculata. This indicates that these gene products may contribute to differences between these two species in sensitivity to antifungals. The results of this study will inform growers of suitable fungicide treatments with respect to outbreak of boxwood blight, depending on the species involved. This work will be used by plant disease management specialists and nursery growers to prevent and control the spread of the boxwood blight disease.

Technical Abstract: Boxwood blight, a disease of ornamental plants (Buxus spp.), is caused by two fungal sister species, Calonectria pseudonaviculata (Cps) and C. henricotiae (Che). Che is less sensitive to fungicides (a quinone outside inhibitor, or QoI, and an azole) than Cps. We used comparative genomics and RNA-Seq analyses to explore the role of polymorphisms and/or gene expression levels in the sensitivity differences to QoI and azole antifungals. We found no polymorphisms associated with reduced QoI sensitivity in other fungi within the cytochrome b gene coding regions of Cps and Che. Seventeen genes were differentially overexpressed in azole-treated Che compared to untreated Che, including homologs of putative xenobiotic detoxification genes such as those encoding monooxygenases and oxidoreductases as well as genes involved in oxidation-reduction reactions. RNA-Seq data confirmed the pseudogene status of Cps CYP51A, as expected based on previous genome sequence analysis. CYP51A was not differentially expressed in Che in response to azole treatment. Of predicted ergosterol biosynthesis genes, two transcripts displayed significant overexpression in Che relative to Cps. Twenty-five predicted detoxification genes were significantly overexpressed in Che on a constitutive basis when compared to Cps. Taken together, our results suggest that expression of a functional CYP51A gene and overexpression of xenobiotic detoxification genes in Che may contribute to differences between these two species in sensitivity to antifungals.