The Primary Study Of The Mechanism Of The Oligosaccharidesinduced Resistance To Pseudomonas Syringaepv.tomato DC3000 In Arabidopsis Thaliana

Elicitor, also known as inducer or plant induced resistance agent, can induceplant defense response.Chitosan oligosaccharides(COS)is an effective plant defence elicitor which can induce plant to resist against pathogen.In this article, the mechanism of the COS induces the resistance of Arabidopsis thaliana against Pseudomonas syringae pv.tomato(Pst DC3000)was studied.The results are as follows:1.The rosette leaves of Arabidopsis thalianawere inoculated with Pst DC3000 after pretreated with 50 μg/mL COS with different pretreatment time.The results showed that the most effective method was using1 mL syringe without needle, the optimum inoculation concentration for Pst DC3000 was OD600 = 0.002, the best pretreatment time of COS was 3 d and sampled at 4d after inoculation.2.In antibacterial test, the direct inhibitory effect of COSon Pst DC3000 was not observed in our experiment. These results suggested that the decreased disease index and Pst DC3000 growth on Arabidopsis-Pst DC3000 interaction, were due to COS could induce the defense response in Arabidopsis instead of inhibit the growth of Pst DC3000 direactly.3.The relative expression of Pst DC3000 marker gene(AvrPtoB,recA) and defense-relative gene(PR1, PDF1.2) were detected by using qRT- PCR method.The results show that the expression of recA and avrPtoB were decreased obviously in COS pretreated group compared with mock-treated group.And the expression of PR1 was strongly activated in COS pretreated group.However, the PDF1.2expression was nearly no changes(without significant difference).4.The content of SA and JA in the rubbed leaves was detected by HPLC-MS method.The results showed that thecontent of SA in theArabidopsis thalianaleaves increased significantly and the JAlevel decreased significantlyin COS pretreated groupcompared with mock-treated group.In summary, COS has no antibacterial activity to plant pathogens in vitro,however,COS could induce the resistance aginst Pst DC3000 in Arabidopsis, After pretreated, COS activated the expression of defense-related(DR) genes PR1 strongly, indicated the COS inducedresistance to Pst DC3000 in Arabidopsis was mainly depended on SA signal pathway. This study aslo provide the primary mechanism of COS on disease resistance in plants...