Functional Study Of PiCreA,a Regulator Of Carbon Catabolite Repression In Penicillium Italicum

Penicillium italicum is an important post-harvest pathogenic fungus of citrus fruit,causing serious post-harvest losses in the citrus industry.The current control methods are chemical pesticides,which may cause environmental pollution and food safety risks.An indepth understanding of the pathogenic mechanism of P.italicum will contribute to the development of new safe and effective prevention and control technologies.For most pathogenic fungi,carbon uptake is essential for growth,development and virulence.Carbon catabolite repression(CCR)is a key mechanism of carbon metabolism,which is mainly regulated by the core transcription factor CreA.The role of PiCreA in P.italicum was investigated.The main results are as follows:1.There is only one filamentous fungus CreA homologue PiCreA in P.italicum.The PicreA gene was 1236 bp in length,with no introns,which encods a protein of 411 amino acids.The PiCreA protein contained two zinc finger domains specific for transcription factors,a partially highly conserved CreA amino acid sequence,and some specific domains associated with regulation.PiCreA performed CCR regulation in P.italicum.PicreA had different expression patterns under different carbon sources.2.Two PicreA deletion mutants were obtained by Agrobacterium tumefaciensmediated transformation.The deletion of PiCreA leads to a decrease in the growth and nutrient utilization of P.italicum.Fungal growth in various carbon source media were generally 30 ~ 50% impaired in the delta PiCreA strain.Except for the delayed spore germination,the conidia formation,germ tube and aerial hyphae growth did not demonstrate obvious changes between mutant strains and the wide type.Under the condition of pectin,the expression of pectinase genes were down-regulated in PiCreA deletion strains.The pathogenicity of P.italicum on citrus fruits showed no matter what kind of inoculation method(spores or hyphae),after the loss of PiCreA,the virulence of P.italicum was almost completely lost.3.Some factors that influence the virulence of PiCreA on P.italicum were preliminarily identified by RNA-seq,including plant resistance responses induced by ?PicreA mutants such as the upregulation of phenylpropanoids,terpenoids and reactive oxygen species.PiCreA may affect the activity of cell wall degrading enzyme and energy metabolism of ?PicreA mutants during infection.In conclusion,PiCreA not only regulates the carbon catabolite repression of P.italicum,but also plays an important role in nutrient utilization and virulence.The results lay the foundation for further investigation of the carbon metabolism pathway of P.italicum and the molecular mechanism of interaction between P.italicum and citrus.