Resistance To Gray Mold Induced By The Active Metabolite RM Of Streptomyces Roseoflavus And Its Signal Transduction Pathway

Antimicrobial active metabolites,Roflamycoin and Men-myco-A(RM)of Streptomyces roseoflavus Men-myco-93-63,is a set of polyene macrolides.In this paper,we mainly uses the disease system of tobacco and Botrytis cinerea to test the induced effect of RM on B.cinerea under different induced resistance ways,different time and concentration.Under the condition of the best way and concentration of induced resistance,the period of induced resistance of RM to gray mould was determined,and the changes of defense enzyme activity and defense related substances content in tobacco were tested too.Quantitative real-time PCR technology were used to detect the relative expression changes of lignin synthesis gene PAL and the pathogenesis-related(PR)genes PR1 and PR5 in tobacco.The quantitative changes of NPR1,PR1,pr1b and PDF1.2 related to the signal transduction pathway of resistance to B.cinerea induced by RM were analyzed.The results are as follows:1.By detecting the induced resistance effect of an active metabolite RM of S.roseoflavus Men-myco-93-63 to gray mould and its induction effect,induction mode,induction time and induction concentration.The results show that the active metabolite RM of S.roseooflavus Men-myco-93-63 can induce the resistance of tobacco to grey mold,and the best inducement method is spray.The best time of inducing is 48 h after RM treatment,and the best inducement concentration is 80 mg/L;Through in vitro blade method,the induced resistance of RM to grey mold was 51.67%under such current test condition;RM could also induce resistance to cucumber gray mold,and the effect was 68.27%.2.Through the tobacco hypersensitive necrosis reaction test,it has confirmed that RM can cause anaphylactic necrosis of tobacco,and it is accompanied by the expression of HR marker gene hsr203j.3.The changes of defense related enzymes,defense related substances,lignin synthesis genes and disease course related PR protein genes in tobacco leaves treated with RM were detected,and we discovered that RM can cause the activity of defense related enzymes dismutase(SOD)and otherwise enzymes increased steadily in tobacco,phenylalanine ammonia lyase(PAL)activity increased gradually in the first two days,then decreased,lipoxygenase(LOX)activity increased significantly in the fifth day,but 0～7 days all of them were higher than the water treatment(CK),lignin content increased,malondialdehyde(MDA)decreased,hydrogen peroxide content at first increased but decreased then;the relative expression of lignin synthesis gene PAL gene was up-regulated,up to 25.37 times than that of the water treatment(CK);the highest relative expression of the pathogenesis-related(PR)gene PR1 gene was at 24 h,which was 11.23 times than that of the water treatment(CK);and the relative expression of PR5 gene was at 72 hours,which was 11.17 times than that of the water treatment(CK).4.The SA pathway marker genes NPR1,PR1a and PR1b in tobacco plants inoculated of Grey mold after RM induction and JA/ET pathway marker gene PDF1.2 were measured by quantitative real-time PCR.The results showed that the NPR1,a key regulatory gene downstream of SA signal transduction pathway,was first activated and continuously overexpressed after RM induction,and then PR-1b and PR-1a genes were continuously overexpressed,indicating that the systemic resistance of tobacco induced by RM to gray mold was achieved by activating SA signal transduction pathway.At the same time,PDF1.2 was activated and overexpressed 24～72 h after RM induction,which indicated that there was a synergistic interaction between SA and JA/ET signaling pathways in the signal transduction process of RM induced tobacco resistance to gray mold.