Destruxin B produced by Alternaria brassicae does not induce accessibility of host plants to fungal invasion

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• 作者：Roxana Y. Parada ; Kumiko Oka ; Daisuke Yamagishi ; Motoichiro Kodama ; Hiroshi Otani
• 关键词：Alternaria brassicae ; Brassica plants ; Destruxin B ; Host-specific or host-selective toxins ; Spore germination fluid ; Infection-inducing activity ; Accessibility ; Colonization
• 刊名：Physiological and Molecular Plant Pathology
• 出版年：2007
• 期刊代码：183_08855765
• 类别：bio
• 出版时间：July-September 2007
• 卷：71
• 期：1-3
• 页码：48-54
• 文件大小：260 K

摘要

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 μg ml⁻¹, and chlorosis or necrosis on non-host leaves at 250–500 μg ml⁻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 μg ml⁻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 (>5 kDa) 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.