A Putative Zn2Cys6 Transcription Factor Is Associated With Isoprothiolane Resistance in Magnaporthe oryzae

Abstract

Isoprothiolane (IPT), a systemic fungicide, has been applied to control rice blast since the 1970s. Although resistance to IPT has been observed, the mechanism of resistance still has not been fully elucidated. In this study, nucleotide polymorphisms were detected between two IPT-resistant mutants generated in the lab, and their parental wild type isolates using a whole-genome sequencing approach. In the genomes of the two resistant mutants, single point mutations were identified in a gene encoding a Zn2Cys6 transcription factor-like protein. Notably, either knocking out the gene or replacing the wild type allele with the mutant allele (R343W) in a wild type isolate resulted in resistance to IPT, indicating that the gene is associated with IPT resistance, and thus was designated as MoIRR (Magnaporthe oryzae isoprothiolane resistance related). Along with point mutations R343W in mutant 1a_mut, and R345C in 1c_mut, a 16 bp insertion in 6c_mut was also located in the Fungal_TF_MHR domain of MoIRR, revealing that this domain may be the core element for IPT resistance. In addition, IPT-resistant mutants and transformants showed cross-resistance with iprobenfos (IBP), which was consistent with previous observations. These results indicated that MoIRR is strongly connected to resistance to choline biosynthesis inhibitor (CBI), and further work should focus on investigating downstream effects of MoIRR.

Unveiling the Role Displayed by Penicillium digitatum PdMut3 Transcription Factor in Pathogen–Fruit Interaction

“…MoIRR is a Zn2Cys6 transcription factor with conserved domains similar to GAL4 and Fungal_TF_MHR present in some of the well-studied Zn2Cys6 transcription factors. The genetic transformation verified that the variation in the MoIRR gene was associated with resistance to the IPT fungicide [24]. In P. digitatum, different Zn 2 Cys 6 transcription factors were identified.…”

“…In this study, we evaluated the possible implication of PdMut3 in the sensitivity to certain fungicides owing to the detected alteration of the cell wall and because many TFs are involved in stress responses and pleiotropic drug resistance [20]. Previous studies performed with MoIRR, a Zn 2 Cys 6 transcription factor of M. oryzae, which has the conserved GAL4-like and Fungal_TF_MHR domains, revealed that the knockout of MoIRR gene did not exhibit relevant differences attributable to variations in pathogenicity/virulence pathogenicity compared with M. oryzae parental isolates, but MoIRR gene was associated with resistance to IPT fungicide [24]. However, the tests carried out in PdMut3 mutants showed that this gene does not have a relevant role in the resistance to fungicides and knockout mutants showed exactly the same resistance pattern for the four chemical compounds tested.…”

The extrachromosomal circular DNAs of the rice blast pathogenMagnaporthe oryzaecontain a wide variety of LTR retrotransposons, genes, and effectors

“…In M. oryzae we found that, out of the 12,115 genes in Guy11, 9,866 were fully contained in an eccDNA forming region in at least one sample. These genes included TRF1 and PTP2 which have been shown to be involved in fungicide resistance in M. oryzae 36, 37 . However, not all genes were observed in eccDNA forming regions at the same frequency.…”

The Fungal Cell Death Regulator czt-1 Is Allelic to acr-3

“…Noteworthy, the acr-2 strain, which also displays increased resistance to acriflavine, harbors a gain-of-function point mutation on another Zn 2 Cys 6 transcription factor (NCU05733) [19]. Zn 2 Cys 6 proteins are fungal specific, constitute the largest family of transcription factors in N. crassa [22] and have been associated with drug resistance in various animal and plant pathogens [20,21,23]. Altogether, our data expand the role of CZT-1 as an important regulator of the fungal response to various drugs.…”