A secreted protease-like protein in Zymoseptoria tritici is responsible for avirulence on Stb9 resistance gene in wheat

Abstract

Zymoseptoria tritici is the fungal pathogen responsible for Septoria tritici blotch on wheat. Disease outcome in this pathosystem is partly determined by isolate-specific resistance, where wheat resistance genes recognize specific fungal factors triggering an immune response. Despite the large number of known wheat resistance genes, fungal molecular determinants involved in such cultivar-specific resistance remain largely unknown. We identified the avirulence factor AvrStb9 using association mapping and functional validation approaches. Pathotyping AvrStb9 transgenic strains on Stb9 cultivars, near isogenic lines and wheat mapping populations, showed that AvrStb9 interacts with Stb9 resistance gene, triggering an immune response. AvrStb9 encodes an unusually large avirulence gene with a predicted secretion signal and a protease domain. It belongs to a S41 protease family conserved across different filamentous fungi in the Ascomycota class and may constitute a core effector. AvrStb9 is also conserved among a global Z. tritici population and carries multiple amino acid substitutions caused by strong positive diversifying selection. These results demonstrate the contribution of an ‘atypical’ conserved effector protein to fungal avirulence and the role of sequence diversification in the escape of host recognition, adding to our understanding of host-pathogen interactions and the evolutionary processes underlying pathogen adaptation.

Quantitative pathogenicity and host adaptation in a fungal plant pathogen revealed by whole-genome sequencing

“…To date, three Z. tritici pathogenicity genes that encode avirulence factors have been cloned. These include AvrStb6 and AvrStb9 that are recognized by the R genes Stb6 and Stb9 , respectively, and lead to a strong qualitative resistance response 12,28,29 , and Avr3D1 which triggers quantitative resistance on cultivars harbouring Stb7 or Stb12 10 . In addition to the above-mentioned R genes, 18 other race-specific Stb resistance genes and numerous quantitative resistance loci have been genetically mapped in wheat 30 , but only Stb6 and Stb16q have been cloned to date 31,32 .…”

Linking Carbendazim Accumulation with Soil and Endophytic Microbial Community Diversities, Compositions, Functions, and Assemblies: Effects of Urea-hydrogen Peroxide and Nitrification Inhibitors

“…The soil N managements of UHP and nitrification inhibitor applications could substantially affect the fungal community assembly, which may be interpreted by the following three reasons: (1) the N management significantly changed the soil abiotic properties to affect fungal community diversities and compositions; , (2) the UHP application has significant influence on the functional genes involved in the N cycling and can alter soil N transformations; and (3) the N management also decreased the soil carbendazim accumulations which generated inconsistent and erratic influences on different fungal taxa. The combination of UHP and DCD significantly enhanced the ratio of Ascomycota , a microbial group that has the special functional genes of protease . The combined applications of UHP and DCD might not only provide exogenous N but also improve soil N availability by decomposing N-containing organic matter …”

Septoria tritici blotch resistance geneStb15encodes a lectin receptor-like kinase

“…5 ). Stb9 has previously been mapped to 2BL 26 but is outside of this locus (at ∼808 Mb) 27 and accessions which display resistance to IPO89011, an isolate which is avirulent on Stb9 , are not always resistant to IPO88004 20,28 ( Supp. Table 7 ).…”