Distinct roles of jasmonates and aldehydes in plant-defense responses.
Distinct roles of jasmonates and aldehydes in plant-defense responses.
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DOI：
10.1371/journal.pone.0001904
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发表时间：
2008-04-02
期刊：
影响因子：
3.7
通讯作者：
Dehesh K
中科院分区：
文献类型：
--
作者：
Chehab EW;Kaspi R;Savchenko T;Rowe H;Negre-Zakharov F;Kliebenstein D;Dehesh K
茉莉酸(Jas)、C6-醛及其相应的衍生物分别由氧化脂质途径的两个主要竞争分支--丙二烯氧化物合成酶(AOS)和氢过氧化氢裂解酶(HPL)分支产生，激活了许多可诱导的植物防御反应。除了对底物的竞争外，这些分支途径衍生的代谢物在基因表达的调节上也有很大的重叠。过去关于C6-醛在植物防御反应中的作用的实验偏向于外源应用合成的代谢物或利用遗传操作来控制HPL的表达水平，在具有完整产生竞争AOS衍生代谢物的能力的植物基因型中。为了分离C6-醛和茉莉酸在介导直接和间接植物防御反应中的作用，我们产生了缺乏这两种代谢物中的一种或两种的拟南芥基因型。随后用一种取食韧皮部的昆虫(蚜虫：桃蚜)、一种食草性昆虫(三叶斑潜蝇)和两种不同的坏死型真菌病原体(Botrytis cinerea和Alternaria brassicicola)挑战这些基因。我们还对这些植物在蚜虫侵染或机械伤害时释放的挥发物进行了表征，并确定了乙酸己烯酯是这些挥发性混合物中的主要化合物。随后，我们研究了该化合物在引诱棉铃虫天敌--棉铃虫寄生蜂中的信号作用。本研究最终确定茉莉酸和C6-醛在植物防御反应中起着不同的作用。茉莉酸是调节植物直接防御反应激活过程中不可缺少的代谢产物，而C6-醛则不是。另一方面，乙酸己烯酯是一种乙酰化的C6-醛，是主要的创伤诱导的挥发性信号，通过引导三元(植物-草食-天敌)相互作用来介导间接防御反应。这些数据表明，茉莉酸酯和乙酸己烯酯在直接和间接植物防御反应中起着不同的作用。这种“分工”的潜在优势是确保最有效的防御策略，即在降低新陈代谢成本的情况下将造成的损害降至最低。
Many inducible plant-defense responses are activated by jasmonates (JAs), C6-aldehydes, and their corresponding derivatives, produced by the two main competing branches of the oxylipin pathway, the allene oxide synthase (AOS) and hydroperoxide lyase (HPL) branches, respectively. In addition to competition for substrates, these branch-pathway-derived metabolites have substantial overlap in regulation of gene expression. Past experiments to define the role of C6-aldehydes in plant defense responses were biased towards the exogenous application of the synthetic metabolites or the use of genetic manipulation of HPL expression levels in plant genotypes with intact ability to produce the competing AOS-derived metabolites. To uncouple the roles of the C6-aldehydes and jasmonates in mediating direct and indirect plant-defense responses, we generated Arabidopsis genotypes lacking either one or both of these metabolites. These genotypes were subsequently challenged with a phloem-feeding insect (aphids: Myzus persicae), an insect herbivore (leafminers: Liriomyza trifolii), and two different necrotrophic fungal pathogens (Botrytis cinerea and Alternaria brassicicola). We also characterized the volatiles emitted by these plants upon aphid infestation or mechanical wounding and identified hexenyl acetate as the predominant compound in these volatile blends. Subsequently, we examined the signaling role of this compound in attracting the parasitoid wasp (Aphidius colemani), a natural enemy of aphids. This study conclusively establishes that jasmonates and C6-aldehydes play distinct roles in plant defense responses. The jasmonates are indispensable metabolites in mediating the activation of direct plant-defense responses, whereas the C6-aldehyes are not. On the other hand, hexenyl acetate, an acetylated C6-aldehyde, is the predominant wound-inducible volatile signal that mediates indirect defense responses by directing tritrophic (plant-herbivore-natural enemy) interactions. The data suggest that jasmonates and hexenyl acetate play distinct roles in mediating direct and indirect plant-defense responses. The potential advantage of this “division of labor” is to ensure the most effective defense strategy that minimizes incurred damages at a reduced metabolic cost.
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