Mapping Of AVR-Pid3 And Functional Analysis Of Four Genes Of Magnaporthe Oryzae Isolate GUY11

Magnaporthe oryzae, the filamentous ascomycete fungus, causes great harm to rice production. However, it is a model organism to study the interaction between pathogen and host mediated by resistance gene and avirulence gene. Avirulence gene can be recognized by the corresponding resistance protein, which triggers the resistance response and inhibits further infection of the pathogen in the host. Therefore, the research of avirulence genes and pathogenicity related genes in the M. oryzae is beneficial for us to understand the mechanisms of the pathogenesis about the fungal pathogen. It may also help us to control rice blast disease more effectively.By pathogenicity test, we found that M. oryzae isolate GUY 11 harbors a novel avirulence gene, AVR-Pid3. The segregation ratio between avirulence and virulence on Pi-d3 in the progeny population of Guyll and FJ81278 （virulent to Pid3） fits to 1:1, which indicated that AVR-Pid3 is controlled by a single locus in GUY11. Based on PATE （Present Absent Transposable Elements） and SSR markers, AVR-Pid3 is positioned between M5 and Ms590. The distance between AVR-Pid3 and the two markers is 4.9 cM and 20.6 cM respectively. The two markers delimited AVR-Pid3 in a 275kb interval. This work laid a good foundation on further fine mapping and cloning of AVR-Pid3.The delimited region were analyzed in the 70-15,GUY11 and FJ81278 databases by bioinformatics methods. Eleven genes encoding small secretory proteins were identified. A number of SNPs and the INDELs sites were found. These results can help fine mapping and cloning AVR-Pid3.MGG₀8817, MGG₁0531, MGG₀3946 and MGG₀3593 are specifically expressed genes in the incompatible interaction. The four genes encode putative secreted proteins,indicating that they might be associated with pathogenicity. Based on gene knockout approach, we analyzed the four genes on mycelial morphology, sporulation and conidial morphology and pathogenicity by camparing with wild type strain GUY11. The results showed that the conidial morphology and pathogenicity were unchanged in all the gene knockout mutants. The sporulation was decreased in the MGG 08817 and MGG 03946 knockout mutants. MGG 10531 knockout mutant colony was deepened in color. MGG₀3593 knockout mutants have no difference with wild type strain. Therefore, MGG₀8817 and MGG₀3946 may be involved in the regulation of sporulation, MGG₁0531 may be associated with pigmentation. The function of these genes needs to be further studied.