Pathogenetic Function Analysis Of Beauvericin In Fusarium Oxysporum On Disease Development Of Banana Fusarium Wilt

Banana(Musa nana Lour.)originated in southern Asia(including southern China)and its cultivar originated from two wild species,M.acuminata Colla and M.balbisiana Colla.Rich local varieties or types have been formed through interspecific or intraspecific hybridization,selection,and evolution.Banana has become the world biggest selling fruit in fresh fruit market.However,Fusarium oxysporum f.sp.cubense tropical race 4(Foc TR4),the causal agent of Fusarium wilt of banana has seriously threatened global banana production.It has been reported that the toxins secreted by Foc TR4 play an important role in its pathogenesis.Among the toxins secreted by Foc TR4,Beauvericin(BEA)is far more toxic than Fusaric acid(FSA),but its pathogenic mechanism remain unclear.Our research team has previously identified that Bbeas is the key gene for the synthesis of BEA,and the pathogenicity of Bbeas-knock-out mutant has significantly decreased.Intensive genetics and functional genomics studies have carried out on the model plant Arabidopsis.Therefore,in order to understanding of the role of BEA in the pathogenesis of Foc TR4,we firstly study the interaction between Arabidopsis and its Fusarium oxysporum Fo5176.The Host-induced gene silencing(HIGS)technology was used to silence the key genes of BEA synthesis,to achieve the purpose of disease resistance and to provide a theoretical basis for future banana diseaseresistant breeding.The detailed results are as follows:(1)Targeting interference of the Foc Bbeas gene: by knocking out the Bbeas homologous gene FOXB?16250 in Fo5176,the virulence of the mutant was decreased.Compared to wildtype strain,the wilting symptom of Colombian Arabidopsis caused by the mutant strain was delayed.Fungal biomass of Foc TR4 was significantly inhibited by the siRNA,which was designed based on the Bbeas gene.(2)HIGS interferes with Foc Bbeas gene: HIGS expression vectors for Arabidopsis and banana were constructed based on the siRNA targets,and the vectors were transformed respectively.Transgenic banana rooting seedlings have been obtained.The obtained Arabidopsis HIGS lines was inoculated with Fo5176 spores and analyzed for disease resistance.The wilt symptom of Arabidopsis was delayed by 2-3 days after inoculation,and the disease incidence was slightly lower than that of wild-type plants.The disease resistance capability and the disease incidence are different among different HIGS lines.(3)Toxicity of BEA on Arabidopsis: the roots of Arabidopsis has became shorter after BEA treatment,which also lead to longer lateral roots and decreased meristems.The result of q RTPCR showed that the DNA replication pathway genes of Arabidopsis roots were upregulated after BEA treatment.