Function Analysis Of Peroxisome Genes FgPex14 And FgPex14/17 In Fusarium Graminearum

Fusarium head blight（FHB） caused by Fusarium graminearum is the important disease on agricultural production, which causes shrinkage of wheat grain, decreases food production. Trichothecene mycotoxins accumulated in the infected grains can also threat the food security, people and animals’ health. Dysfunction of peroxisome because of PEX genes abnormalities can cause fatal peroxisome biogenesis disorders in mammals and result in growth abnormalities, lower pathogenicity in plant pathogenic fungi. Therefore, further research on PEX gene function in F. graminearum s. str. will be conducive to elucidate its mycotoxin synthesis and pathogenic mechanism, and be of great significance to explore comprehensive prevention way, develop new fungicide and reduce mycotoxin contamination.This study is based on the method of reverse genetic. After homologous sequence alignment with model organism Saccharomyces cerevisiae, we have chosen Fg Pex14 and Fg Pex14/17 genes as the research object, which play an important role in peroxisome metabolism. We have obtained the gene deletion mutation strains and complementary strains by the method of PEG mediated protoplast transformation and homologous recombination. Through studies of various phenotypes in Fusarium graminearum s. str., we reveal the fuctions of Fg Pex14 and Fg Pex14/17 genes.1. Genes deletion complementary mutants of Fg Pex14 and Fg Pex14/17 were obtained.Through the method of gene sequences alignment, we have obtained homologous genes Fg Pex14（FGSG₀9263） and Fg Pex14/17（FGSG₀4329）. Then we constructed genes knockout vectors and complementary vectors. By the method of PEG mediated protoplast transformation and homologous recombination, we have obtained the gene deletion mutation strains and complementary strains.2. Fg Pex14 gene is involving in the growth development, matrix proteins import and pathogenicity in Fusarium graminearum s. str.ΔFg Pex14 showed a lower growth rate, less aerial hyphae and the amount of spore production. The mutants showed a reduced ability of using long and short chain fatty acid, especially the long chain fatty acid. They lost the ability of sexual reproduction. These results showed that deletion of Fg Pex14 gene affected growth development of F. graminearum s. str. Compared with wild type strain, the mutants could produce fewer toxins and could not penetrate cellophane. They increased ROS accumulation, reduced viability and virulence on wheat was reduced. Deletion of the Fg Pex14 gene completely blocked the matrix proteins import through PTS1 and PTS2 signal pathways. In sensitivity tests to various stresses, ΔFg Pex14 has decreased the sensitivity to glucose, Li Cl and increased the sensitivity to caffeine, H2O2, tebuconazole and so on. These results showed that deletion of Fg Pex14 gene affected resistance to various stresses of F. graminearum s. str.3. Fg Pex14/17 gene is involving in the growth development, matrix proteins import and pathogenicity in Fusarium graminearum s. str.ΔFg Pex14/17 showed a lower growth rate, less aerial hyphae and the amount of spore production. The mutants showed a reduced ability of using long and short chain fatty acid, especially the long chain fatty acid. They reduced the ability of sexual reproduction. These results showed that deletion of Fg Pex14/17 gene affected growth development of F. graminearum s. str. Compared with wild type strain, the mutants could produce fewer toxins and have reduced the ability of cellophane penetration, increased ROS accumulation and showed early necrocytosis. Virulence on wheat was reduced. Deletion of the Fg Pex14/17 gene could not completely block the matrix proteins import through PTS1 and PTS2 signal pathways. A part of matrix proteins still be imported into peroxisome. In addition, we found that C-terminally truncated version of Fg Pex14/17 p control PTS1 signal pathways and N-terminally truncated version of Fg Pex14/17 p control PTS2 signal pathways. It was first found that N-terminally truncated version of Pex14/17 p has effect on PTS2 signal pathways in filamentous fungi. In sensitivity tests to various stresses, ΔFg Pex14/17 has decreased the sensitivity to glucose, calcofluor white and increased the sensitivity to caffeine, H2O2, tebuconazole and so on. These results showed that deletion of Fg Pex14/17 gene also affected resistance to various stresses of F. graminearum s. str.Our study showed the Fg Pex14 and Fg Pex14/17 genes have played an important role in the growth development, matrix proteins import and pathogenicity in Fusarium graminearum s. str. Research on Fg Pex14 and Fg Pex14/17 genes’ function in F. graminearum s. str. provides theoretical basis for elucidating its mycotoxin synthesis and pathogenic mechanism.