Preliminary Study On The Regulatory Function Of OsAGO2 On Rice Black-streaked Dwarf Disease And MicroRNA164a On Rice Stripe Disease Resistance

Rice black-streaked dwarf virus(RBSDV)and Rice stripe virus(RSV)are two viruses transmitted by small brown planthoppers(SBPH,Laodelphax striatellus).They seriously endanger the production of crops.Cultivating disease-resistant varieties is the most economical and effective means of preventing and controlling virus diseases.Therefore,the identification of resistance genes to rice black-streaked dwarf disease and rice stripe disease and the breeding of resistant varieties are of great significance to the current safety of rice production.In this study,RBSDV and RSV were selected as the research objects,and the interactions between OsAGO2 and RBSDV,mi R164 a and RSV were studied respectively,and the mode of action of OsAGO2 in regulating RBSDV and mi R164 a in regulating RSV was preliminarily determined.In addition,this study also found that during the process of RBSDV infecting rice,mutations in OsAGO2 induce the activation of defense responses.At the same time,three target genes of mi R164 a after RSV infection in rice were initially screened.The main research contents are as follows:1.Preliminary Study on the Regulatory Function of OsAGO2 on Rice black-streaked dwarf disease ResistanceThe Argonaute(AGO)protein plays a vital role in plant defense against virus invasion.So far,the role of OsAGO2 in rice antiviral defense is still unclear.In this study,we compared the expression of several AGO genes in non-toxic SBPH infection and RBSDV-infected NPB plants,and found that OsAGO2 was up-regulated after RBSDV infection.Through artificial inoculation of OsAGO2 overexpression transgenic plants and osago2 mutant plants with RBSDV for resistance identification,it was found that overexpression of OsAGO2 would enhance the sensitivity of rice to RBSDV,and mutation of OsAGO2 would enhance the resistance of rice to RBSDV.This study also conducted an insect resistance analysis on OsAGO2 transgenic rice,and found that OsAGO2 could not regulate rice resistance to SBPH,indicating that OsAGO2 mediates resistance to RBSDV by regulating the virus rather than SBPH.Finally,by examining the expression of defense genes(Os NPR1,Os PR1 a and Os PR1b)and the accumulation of reactive oxygen species,it was found that during the process of RBSDV infecting rice,mutations in OsAGO2 causes early activation of defense responses,indicating that OsAGO2 negatively regulates rice resistance immunity.2.Preliminary Study on the Regulatory Function of Micro RNA164 a on Rice stripe disease ResistanceIt is of great significance to study the regulation mechanism of rice endogenous mi RNAs to the defense response of rice stripe disease,and to breed resistant varieties and disease control.This study compared the expression of mi R164 a in NPB plants infected with nontoxic SBPH and RBSDV,and found that mi R164 a would response to RSV infection.The mi R164 a overexpression transgenic rice was artificially inoculated with RSV for resistance identification.It was found that the overexpression of mi R164 a would enhance the resistance of rice to RSV.Preliminary screening of the target genes of mi R164 a upon RSV infection.It is found that after RSV infection,Os NAC11,Os NAC60 and Os NAC104 are induced to express in a manner opposite to the expression pattern of mi R164 a.These three genes are preliminarily determined as target genes of mi R164 a.In summary,on the one hand,this study found that OsAGO2 can negatively regulate the immunity of rice to RBSDV,and the osago2 mutant lines exhibits disease resistance to RBSDV infection by inducing an early defense response.On the other hand,this study found that mi R164 a can positively regulate the rice immunity to RSV,and initially screened the target genes of mi R164 a during RSV infection.The findings of this study provide new ideas for the study of rice virus resistance genes and the control of rice virus diseases.