Study On The Function Of G Protein α Subunit In Ustilago Esculenta

Ustilago esculenta can infect Zizania latifolia and make its stem base expand to form edible fleshy stem--Jiaobai.Jiaobai is an important aquatic vegetable in China,which is widely planted in the south of the Yangtze River Basin and has rich nutritional value.Previous studies had demonstrated that U.esculenta is a typical dimorphic fungus,which was existed in yeast form and filament form.The haploid of U.esculenta is yeast type,which propagates in budding way.When two yeast form haploids with different mating genes recognize each other,they begin to form conjugation tubes and dikaryotic filament with pathogenicity.In fungi,the G protein signaling pathway has been confirmed to be involved in many important physiological processes such as mycelial morphological differentiation,pathogenicity and secondary metabolite synthesis.G protein is composed of α,β and γ subunits,among which α subunits contain GTP binding sites and GTPase activity.The activation of G protein by G protein coupled receptor leads to the binding of GTP and Gα subunit,and the binding of GTP leads to the dissociation of Gα·GTP and Gβγ subunit,and the activation of downstream effectors by Gα·GTP and Gβγ subunit leads to a series of signal transduction.At present,there is no study on Gα subunit in U.esculenta.The study on the function of G protein αsubunit in U.esculenta can provide a basis for the study of signal transduction and pathogenic mechanism of U.esculenta.In this study,four genes,Uegpa1,Uegpa2,Uegpa3 and Uegpa4,encoding theα subunit of G protein,were cloned from U.esculenta.They all have typical Gαdomain,and they have high homology with Gpa1,Gpa2,Gpa3 and Gpa4 of Ustilago maydis.The expression pattern analysis showed that Uegpa1,Uegpa2,and Uegpa4 had no significant difference compared with the control group,but Uegpa3 was up-regulated during the formation of the junction tube;the deletion mutants of the above four strains were constructed and fused in vitro,and it was found that the absence of Uegpa1,Uegpa2,and Uegpa4 did not affect the fusion,while the absence of Uegpa3 would affect the formation of the junction tube and then affect the fusion of the strains;inoculation experiment found that the absence of Uegpa3 would affect the pathogenicity of wild Jiaobai,but the specific mechanism was not clear.Further study showed that Uegpa3 in U.esculenta can affect the signal transmission of pheromone and ultimately affect the dimorphic transition.It may affect the expression of mfa gene by regulating the induced expression of Ue Prf1 through MAPK signal pathway,resulting in the formation of junction tube blocked and the strain could not be fused.However,the specific mechanism should be further studied.This study preliminarily explored the function of G protein α subunits in U.esculenta,and discussed its role in dimorphic transition,which provide basic material for the research on the interaction mechanism between the U.esculenta and Z.latifolia.