| Ste12 genes is a transcription factor regulated by Fus3/Kss1-MAPK pathway,which plays an important role in regulating fungal growth and pathogenesis.Glomerella Leaf Spot is a new pandemic disease that spread across main apple production areas in China.This disease spreads rapidly and causes huge economic losses to the China apple industry.Colletotrichum fructicola is the main pathogen.In order to define the roles of C.fructicola Ste12 gene in regulating fungal growth and pathogenesis,we generated gene knock out mutants based on homologous recombination and split-marker PCR in two strains with different phenotypes,1104-6,1104-7.mutant phenotypes were compared with the wild type and genetic complementation was performed.Obtained main results were listed below:The C.fructicola Ste12 protein contains STE homeodomain and zinc finger domain,similar as known homologs in filamentous fungi.Compared with the wild type,Ste12 gene deletion did not affect the colony morphology,mycelial growth rate,conidium production,appressorium formation,but significantly reduced conidium germination rate and appressorium formation rate.Moreover,the mutants failed to penetrate onion epidermis and were non-pathogenic toward apple leaves and fruits.When doing wounding inoculation on apple fruit,the mutants could colonize and cause bitter fruit rot symptom,but the lesion sizes were much smaller than the wild type.We also found that a certain proportion of conidia produced swelled secondary branching hyphae instead of appressorium upon germination.In terms of sexual reproduction,the mutants produced perithecia smaller than wild type,and the shape was irregular;within the perithecium,no ascus or ascospore were formed.Taken togetherour results suggested that the C.fructicola Ste12 transcription factor regulates many steps of pathogenesis,including conidium germination,appressorium,penetration,and colonization,Ste12 also controls the developments of sexual fruiting body perithecium,as well as ascus and ascospore. |
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