Fungicide efflux and the MgMFS1 transporter contribute to the multidrug resistance phenotype in Zymoseptoria tritici field isolates

Abstract

Septoria leaf blotch is mainly controlled by fungicides. Zymoseptoria tritici, which is responsible for this disease, displays strong adaptive capacity to fungicide challenge. It developed resistance to most fungicides due to target site modifications. Recently, isolated strains showed cross-resistance to fungicides with unrelated modes of action, suggesting a resistance mechanism known as multidrug resistance (MDR). We show enhanced prochloraz efflux, sensitive to the modulators amitryptiline and chlorpromazine, for two Z. tritici strains, displaying an MDR phenotype in addition to the genotypes CYP51(I381V Y461H) or CYP51(I381V ΔY459/) (G460) , respectively, hereafter named MDR6 and MDR7. Efflux was also inhibited by verapamil in the MDR7 strain. RNA sequencing lead to the identification of several transporter genes overexpressed in both MDR strains. The expression of the MgMFS1 gene was the strongest and constitutively high in MDR field strains. Its inactivation in the MDR6 strain abolished resistance to fungicides with different modes of action supporting its involvement in MDR in Z. tritici. A 519 bp insert in the MgMFS1 promoter was detected in half of the tested MDR field strains, but absent from sensitive field strains, suggesting that the insert is correlated with the observed MDR phenotype. Besides MgMfs1, other transporters and mutations may be involved in MDR in Z. tritici.

Multiple facets of response to fungicides – the influence of azole treatment on expression of key mycotoxin biosynthetic genes and candidate resistance factors in the control of resistant Fusarium strains

“…The major facilitator superfamily (MFS) transporter involvement was also noted in other plant pathogenic species e.g. in Botrytis cinerea (Bcmfs1 - Hayashi et al 2002) and Zymoseptoria tritici (MgMFS1 - Omrane et al 2015).…”

Plasticity of theMFS1promoter leads to multi drug resistance in the wheat pathogenZymoseptoria tritici

“…Reporting all SNPs and INDELS of the resistant 359 bulks R2 and R3 present in this bin on the local alignment between contig 1135 and the 360 IPO323 very left arm of chromosome 7, we identified three kinds of polymorphic sites: those 361 common to both MDR strains and those independent to each of them (Table S3) shown). Indeed, we had previously found that both strains harbor a 519 bp insert in the MFS1 373 promoter region (Omrane et al, 2015). 374…”

“…In our previous study, we identified MFS1 as a major player in Z. tritici multidrug resistance 553 (Omrane et al, 2015) and had found a retro-transposon relic as an insert in the MFS1 554…”

“…In both analyzed MDR strains, a 519 bp insert was detected in the MFS1 promoter, 82 a putative reminiscence of an ancient LTR-retrotransposon. Other, but not all field MDR 83 strains, proved to have this promoter insert as well, suggesting a potential role in MDR 84 (Omrane et al, 2015). In this study we address the question of the mutations responsible for 85 the MDR phenotype in the previously characterized MDR strains.…”

“…http://dx.doi.org/10.1101/174722 doi: bioRxiv preprint first posted online Aug. 10, 2017; In a recent study we have shown that fungicide efflux was at work in two Z. tritici MDR field 76 isolates (Omrane et al, 2015). Both strains, as well as other MDR strains tested, 77 constitutively overexpress the gene MFS1 (originally named MgMFS1 for Mycosphaerella 78 graminicola MFS1) encoding an MFS transporter, capable to transport a wide diversity of 79 molecules (Roohparvar et al, 2008).…”