부산대학교 도서관

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.pmpp.2007.10.003 Byline: Roxana Y. Parada (a), Kumiko Oka (b), Daisuke Yamagishi (b), Motoichiro Kodama (b), Hiroshi Otani (b) Keywords: Alternaria brassicae; Brassica plants; Destruxin B; Host-specific or host-selective toxins; Spore germination fluid; Infection-inducing activity; Accessibility; Colonization Abstract: It has been reported that Alternaria brassicae, the causal agent of gray leaf spot in Brassica plants, produces a host-specific or host-selective toxin (HSTs) identified as destruxin B. In this study, the role of destruxin B in infection of the pathogen was investigated. Destruxin B purified from culture filtrates (CFs) of A. brassicae induced chlorosis on host leaves at 50-100[mu]gml.sup.-1, and chlorosis or necrosis on non-host leaves at 250-500[mu]gml.sup.-1. Destruxin B was detected in spore germination fluids (SGFs) on host and non-host leaves, but not in a sufficient amount to exert toxicity to host plants. When spores of non-pathogenic A. alternata were combined with destruxin B at 100[mu]gml.sup.-1 and inoculated on the leaves, destruxin B did not affect the infection behavior of the spores. Interestingly, SGF on host leaves allowed non-pathogenic spores to colonize host leaves. Moreover, a high molecular weight fraction (>5kDa) without destruxin B obtained by ultrafiltration of SGF had host-specific toxin activity and infection-inducing activity. From these results, we conclude that destruxin B is not a HST and does not induce the accessibility of the host plant which is essential for colonization of the pathogen. In addition, the results with SGF imply that a high molecular weight HST(s) is involved in the host-pathogen interaction. Author Affiliation: (a) The United Graduate School of Agricultural Sciences, Tottori University, Tottori 680-8553, Japan (b) Faculty of Agriculture, Tottori University, 4-101 Koyama-Minami, Tottori 680-8553, Japan Article History: Accepted 19 October 2007