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.
Highlights
Rice is the most important crop worldwide, as it is the main staple food for more than half of the human population, and more than 3.5 billion people may consume rice every day
Only mutations in one gene were detected in both 1a_mut and 1c_mut (Tables S2, S3). This gene encodes a protein with the GAL4-like binuclear cluster DNA-binding domain originally found in GAL4, GAL4 is a positive regulator for the expression of galactose-induced genes in Saccharomyces cerevisiae (Kraulis et al, 1992), and a Fungal_TF_MHR domain
All resistant mutants and transformants showed similar pathogenicity as the wild type isolates (Figure 4). These results indicated that no significant fitness penalties were observed in resistant mutants and transformants compared to sensitive wild type isolates, suggesting that MoIRR is not essential for survival
Summary
Rice is the most important crop worldwide, as it is the main staple food for more than half of the human population, and more than 3.5 billion people may consume rice every day. The demand for rice is growing dramatically in Asia and Africa, due to explosive population growth. This is not matched by increasing yield, and the situation is worsened by losses to various pathogens or pests. Rice blast caused by the ascomycete fungus Magnaporthe oryzae is one of the most devastating diseases of rice. It leads to tremendous losses in yield and decreased quality of harvested rice, threatening world food security (Wilson and Talbot, 2009; Dean et al, 2012). Wheat blast is a regional disease and a potential global crop disease (Tufan et al, 2009)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
