Study On Transcriptome Analysis Of Rice Treated With Abscisic Acid,Jasmonic Acid And Mechanisms Of Rice Resistance To Brown Planthopper(BPH),Nilaparvata Lugens St(?)l(Hemiptera:Delphacidae)

Abscisic acid(ABA)is one of five major hormones in plants,and it is also a plant-derived biochemical pesticide.ABA can enhance plant resistance to abiotic stresses,and also plays an important role in resistance to biotic stresses such as pathogens,viruses and pests.ABA plays a more complex role in plant response to pathogen infection,which may be beneficial to plant disease resistance or induce plant susceptibility depending on ABA concentration and application time.Hormone signals in plants interact with each other,which can promote or antagonize each other.Previous studies had found that one of the mechanisms of ABA defense against pathogens was to participate in the biosynthesis of jasmonic acid(JA)and activate JA-mediated expression of disease-resistant genes.In other words,ABA interacted with JA.The brown planthopper(BPH),Nilaparvata lugens Stal(Hemiptera:Delphacidae)is a piercing-sucking pest,and damages rice through sucking phloem juice.Thus BPH feeding is similar to the pathogen infection.ABA and JA could interact with each other against BPH.This paper studied transcriptome analysis of ABA and JA treated rice after BPH feeding,and the role of interaction between ABA and JA in rice resistance to BPH.The effects of ABA biosynthetic inhibitor fluridone(FLU)on the feeding and reproduction of BPH in rice were also studied,which may provide a new approach to the mechanism of rice resistance to BPH.The results were as follows:1.Transcriptome analysis of rice after ABA,JA treatment and BPH feedingNumbers of differentially expressed genes treated with ABA,JA,BPH,BPH+ABA and BPH+JA were 1004,144,10692,5425 and 5499,respectively.GO functional annotation showed that the distribution of differentially expressed genes was consistent among the five groups.The most abundant functions of differentially expressed genes in cellular component,molecular function and biological process classification were cell and cell part,catalytic activity and binding,metabolic process and cell process,respectively.KEGG pathway enrichment analysis showed that the pathways of flavone and flavonol biosynthesis were highly enriched after ABA,BPH,BPH+ABA and BPH+JA treatment.After ABA treatment,the biosynthesis of secondary metabolites and plant hormone signal transduction pathways involved in the most differential genes.In plant signal transduction pathway,OsbZIP23 and OsPP2Cs related to plant stress resistance were up-regulated,which could be one of the reasons why ABA enhanced plant stress resistance.OsKSL4,a rice lactone biosynthesis gene,was up-regulated in secondary metabolite synthesis pathway after ABA treatment,which could be one of the important ways for ABA to enhance plant defense response.OsMYC2,a transcription activator of JA signal pathway,was down-regulated after BPH+ABA treatment,and it could be the key gene for the interaction between ABA and JA.OsMYC2,OsABA8ox2 and OsIAA23 were selected for real-time quantitative PCR verification.After BPH+ABA treatment,the expression of OsMYC2 significantly reduced,and after ABA treatment,the expression of OsABA8ox2 significantly increased and OsIAA23 significantly decreased.The results were consistent with the result of transcriptome sequencing,which proved the accuracy of transcriptome data.After BPH+ABA treatment,OsMYC2 differentially expressed and involved in MAPK signaling pathway-plant,plant-pathogen interaction and plant hormone signal transduction pathway,indicating that OsAMYC2 may plays an important role in plant hormone interaction and plant diseases.2.The role of ABA and JA interaction in rice resistance to BPHAfter ABA and BPH+ABA treatments,the expression of OsZEP was significantly decreased,but the expression of OsNCED5 was significantly increased,compared with the control.The expressions of OsABA8oxl and OsABA8ox3(ABA decomposition key genes)were significantly increased,and the expression of ABA receptor gene OsPYL4 was significantly decreased.This may be due to the up-regulation of key gene for ABA decomposition,down-regulation of key ABA synthesis gene OsZEP and receptor gene OsPYL4 of response in rice to high concentrations of ABA.Without BPH feeding,ABA treatment facilitated JA synthesis,down-regulated the expression of JA transcription inhibitor OsJAZl,and there was a synergism between ABA and JA.After BPH+ABA treatment,ABA content in rice increased and JA content decreased,the expression of JA transcription activator OsMYC2 decreased significantly,which indicated that ABA and JA had antagonism.3.Effects of FLU on BPH feeding and reproduction after application on riceFLU is a pyrrolidone herbicide and also an ABA biosynthesis inhibitor.After BPH feeding on the susceptible rice cultivar TN1 treated with 15 ?mol/L FLU,the duration of N4 wave(sap ingestion in the phloem)was significantly longer than that of the control,but after BPH feeding on the FLU-treated medium-resistant rice cultivar IR42,the duration of N4 wave had no significant change.There was no significant change in the reproductive capacity of the two rice cultivars treated with FLU,but the deposition area of callose decreased significantly.FLU promoted BPH feeding on TN1,inhibited the deposition area of callose in TN1 and IR42,and reduced the rice resistance to BPH,which provided supplementary evidence that ABA promoted plant resistance to BPH.