Preliminary Study On The Alginate Oligosaccharide Induced Plant Resistance And Its Mechanisms

Alginate oligosaccharide(AOS)are marine oligosaccharides generated by the degradation of alginate and are composed of ?-L-guluronate and ?-D-mannuronate or a mixed sequence of both residues.It can promote plants growth,drought resistance and so on.However,it is lack of study of AOS on the disease resistance induction,which limits the further development and application of AOS in agricultural production.This study aimed to investigate the effects of AOS on inducing resistant to Pseudomonas syringae pv.tomato DC3000 in Arabidopsis thaliana plant and tobacco mosaic virus(TMV)in Nicotiana tabacum var.samsun NN and N.tabacum cv.Huangmiaoyu nn plant.By detecting the indexes related to plant defense,to explore the AOS mechanism,hope to get good biological preparations.The result showed as follows:1.In case of Arabidopsis,plants were pretreated with 25-200 mg/L AOS at three days before inoculation of Pst DC3000.25 mg/L AOS showed induction activity against Pst DC3000 compared to control,the disease index decreased by 35.62 % and the inhibition ratio of pathogen growth is 78.88 %.2.AOS have no inhibition effect on pathogen growth in vitro,but AOS significantly inhibit the proliferation of bacteria in the leaves of Arabidopsis,meanwhile,the expression of AvrPtoB and RecA decreased in AOS pretreated plant.3.In AOS pretreated group,the plant defense pathway was influenced.PR1 and PDF1.2 genes were significantly increased 10.57 and 4.59 folds compared to control group.The salicylic acid content increased about 20.72 % in AOS pretreated plant.4.In AOS pretreated group,the desease indexes of Sid2 Arabidopsis were decreased,the relative expression of AvrPtoB and RecA also decreased,however,the defense induction activity of AOS in sid2 mutant is much less compared to control group.5.In case of tobacco plant,AOS induce resistance to TMV in resistant varieties with the optimal concentration of 50 mg/L,and the inhibition rate of necrotic lesion was 19.59 %.AOS also induced susceptible varieties against TMV.The coat protein gene and protein expression of TMV in both local and systemic leaves were decreased,indicating that AOS can induce tobacco to inhibit the reproduction and transport of the virus in vivo.