Induction of Defense Responses by Synthetic Glycopeptides that Have a Partial Structure of the Elicitor in the Spore Germination Fluid of Mycosphaerella pinodes

A high molecular weight elicitor (>70kDa)from spore germination fluid of a pea pathogen, Mycosphaerella pinodes, has a partial structure of /J-D-G1C-(1 - 6)-a-DMan-( 1 - 6)-D-Man, which is O-glycosidically attached to serine in the protein moiety. To elucidate the minimum structure for the elicitor activity to pea plants, the effects of nine glycopeptides including /?-D-G1C-(1 - 6)-a-D-Man- (1 -< 6)-D-Man-0-Ser (No. 1)to [/?-D-G1C-(1 -* 6)-a-D-Man- (1 -* 6)-D-Man]3-O-Ser3-Pro3 (No. 9)on the infection by M. pinodes, superoxide generation and ATPase activity were measured. The glycopeptides [/?-D-G1C-(1 -> 6)-a-n- Man-(1 -» 6)-D-Man]-0-Ser2-Pro2 (No. 3)to No. 9 induced rejection reaction of pea tissue against M.pinodes. The glycopeptides No. 3 to No. 9 also induced superoxide generation on uninjured pea leaves. Moreover, the glycopeptides No. 3 to No. 9 induced in vitro the activation of cell wall-bound ATPase and superoxide generation system in the protein fraction solubilized from pea cell wall. The results indicate that the synthetic glycopeptides, No. 3 to No. 9, are available to analyze the signal transduction cascade leading to defense responses and the receptor for the elicitor.