Research On The Biochemical And Molecular Mechanism Of Induced Defense Responses Of Wheat Infested By Sitobion Avenae

Herbivore-induced plant defense responses are important parts of interaction mechanism between insect and host plant In order to study the defense responses in wheat,we choose aphid-wheat as interaction system to detect the activities of key enzymes (lipoxygenase, polyphenoloxidase, phenylalanine ammonia-lyse and β -1,3-glucanase) and the transcripts of key defence genes(genes for farnesyl pyrophosphate synthetase, allene oxide synthase, phenylalanine ammonia-lyse) under pressure of aphid-feeding, aphid-induced volatiles,specific volatiles at biochemical(using enzymes assay) and molecular (using RT-PCR and real-time quantitative PCR) levels respectively.At the same time, both enzymes activities and the transcripts of defence genes induced by artificial wounding, wounding-induced volatiles and chemical inductive substances(jasmonic acid and methyl-salicylate) are also detected for comparison.Finally,we confirm the defense reponses and signalling transduction pathways in wheat elicited by aphid-feeding and aphid-induced volatiles.The results are as follows:The activities of key enzymes which belongs to both jasmonic acid(JA) and salicylic acid (SA)-signalling pathways increase significantly after aphid-feeding.The relative expressions of key defence genes in the signaling pathways above are also enhanced.So we propose that aphid-feeding activates both jasmonic acid(JA) and salicylic acid (SA)-signalling transductive pathways. Artificial wounding and aphid-feeding are not equivalent.Sitobion avenae-induced volatiles induce only the increase of LOX activity in neighbouring plants,but elicit the transcription of all the three defence genes.The mechanism is that volatiles might induce the activity of LOX followed by activation of JA signaling pathway and then expression of multiple defence genes that JA mediates.6-methyl-5-hepten-2-one,2-tridecanone and (E)-3-hexen-l-ol in Sitobion avenae-induced volatiles are not only closely related to the expression of defence genes.but also influence aphid feeding and population trend.These achievements have important theoretic and practical significance on the foundation of rapid molecular detection technique about wheat induced resistance.further studying of resistant mechanism and exploration of new control method which makes use of the volatiles and chemical inductive substance.