Kim Jae Hak, Jander Georg
Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853, USA.
Plant J. 2007 Mar;49(6):1008-19. doi: 10.1111/j.1365-313X.2006.03019.x. Epub 2007 Jan 26.
Cruciferous plants produce a wide variety of glucosinolates as a protection against herbivores and pathogens. However, very little is known about the importance of individual glucosinolates in plant defense and the regulation of their production in response to herbivory. When Myzus persicae (green peach aphid) feeds on Arabidopsis aliphatic glucosinolates pass through the aphid gut intact, but indole glucosinolates are mostly degraded. Although aphid feeding causes an overall decrease in Arabidopsis glucosinolate content, the production of 4-methoxyindol-3-ylmethylglucosinolate is induced. This altered glucosinolate profile is not a systemic plant response, but is limited to the area in which aphids are feeding. Aphid feeding on detached leaves causes a similar change in the glucosinolate profile, demonstrating that glucosinolate transport is not required for the observed changes. Salicylate-mediated signaling has been implicated in other plant responses to aphid feeding. However, analysis of eds5, pad4, npr1 and NahG transgenic Arabidopsis, which are compromised in this pathway, demonstrated that aphid-induced changes in the indole glucosinolate profile were unaffected. The addition of purified indol-3-ylmethylglucosinolate to the petioles of cyp79B2 cyp79B3 mutant leaves, which do not produce indole glucosinolates, showed that this glucosinolate serves as a precursor for the aphid-induced synthesis of 4-methoxyindol-3-ylmethylglucosinolate. In artificial diets, 4-methoxyindol-3-ylmethylglucosinolate is a significantly greater aphid deterrent in the absence of myrosinase than its metabolic precursor indol-3-ylmethylglucosinolate. Together, these results demonstrate that, in response to aphid feeding, Arabidopsis plants convert one indole glucosinolate to another that provides a greater defensive benefit.
十字花科植物会产生多种芥子油苷，以此抵御食草动物和病原体。然而，关于单个芥子油苷在植物防御中的重要性以及其在应对食草作用时的产生调控，我们所知甚少。当桃蚜（Myzus persicae）取食拟南芥时，脂肪族芥子油苷会完整地穿过蚜虫肠道，但吲哚族芥子油苷大多会被降解。尽管蚜虫取食会导致拟南芥芥子油苷含量整体下降，但4-甲氧基吲哚-3-基甲基芥子油苷的产量却会被诱导增加。这种芥子油苷谱的改变并非植物的系统性反应，而是局限于蚜虫取食的区域。蚜虫取食离体叶片会导致芥子油苷谱发生类似变化，这表明观察到的变化并不需要芥子油苷的运输。水杨酸介导的信号传导与植物对蚜虫取食的其他反应有关。然而，对该信号通路存在缺陷的eds5、pad4、npr1和NahG转基因拟南芥的分析表明，蚜虫诱导的吲哚族芥子油苷谱的变化并未受到影响。将纯化的吲哚-3-基甲基芥子油苷添加到不产生吲哚族芥子油苷的cyp79B2 cyp79B3突变体叶片的叶柄上，结果表明这种芥子油苷是蚜虫诱导合成4-甲氧基吲哚-3-基甲基芥子油苷的前体。在人工饲料中，在没有黑芥子酶的情况下，4-甲氧基吲哚-3-基甲基芥子油苷对蚜虫的威慑作用明显大于其代谢前体吲哚-3-基甲基芥子油苷。这些结果共同表明，响应蚜虫取食时，拟南芥植物会将一种吲哚族芥子油苷转化为另一种具有更大防御益处的芥子油苷。
