Department of Biochemistry, Max Planck Institute for Chemical Ecology, 07745, Jena, Germany.
Department of Genetics, University of Georgia, Athens, GA, 30602, USA.
New Phytol. 2022 Jul;235(2):701-717. doi: 10.1111/nph.18148. Epub 2022 Apr 30.
Salicylic acid (SA) and jasmonic acid (JA) often play distinct roles in plant defence against pathogens. Research from Arabidopsis thaliana has established that SA- and JA-mediated defences are more effective against biotrophs and necrotrophs, respectively. These two hormones often interact antagonistically in response to particular attackers, with the induction of one leading to suppression of the other. Here, we report a contrasting pattern in the woody perennial Populus: positive SA-JA interplay. Using genetically engineered high SA lines of black poplar and wild-type lines after exogenous hormone application, we quantified SA and JA metabolites, signalling gene transcripts, antifungal flavonoids and resistance to rust (Melampsora larici-populina). Salicylic acid and JA metabolites were induced concurrently upon rust infection in poplar genotypes with varying resistance levels. Analysis of SA-hyperaccumulating transgenic poplar lines showed increased jasmonate levels, elevated flavonoid content and enhanced rust resistance, but no discernible reduction in growth. Exogenous application of either SA or JA triggered the accumulation of the other hormone. Expression of pathogenesis-related (PR) genes, frequently used as markers for SA signalling, was not correlated with SA content, but rather activated in proportion to pathogen infection. We conclude that SA and JA pathways interact positively in poplar resulting in the accumulation of flavonoid phytoalexins.
水杨酸（SA）和茉莉酸（JA）通常在植物抵御病原体的防御中发挥独特的作用。拟南芥的研究已经确定，SA 和 JA 介导的防御分别对生物寄生物和坏死生物更有效。这两种激素通常在对特定攻击者的反应中相互拮抗，一种激素的诱导会抑制另一种激素的产生。在这里，我们报告了一个在木本多年生杨树中截然不同的模式：SA-JA 之间存在积极的相互作用。通过对黑杨的遗传工程高 SA 系和外源激素处理后的野生型系进行研究，我们量化了 SA 和 JA 代谢物、信号基因转录物、抗真菌类黄酮和对锈病（Melampsora larici-populina）的抗性。在具有不同抗性水平的杨树基因型中，锈病感染会同时诱导 SA 和 JA 代谢物的产生。对水杨酸超积累转基因杨树系的分析表明，茉莉酸水平升高，类黄酮含量增加，锈病抗性增强，但生长没有明显下降。外施 SA 或 JA 都会触发另一种激素的积累。常被用作 SA 信号标志物的病程相关（PR）基因的表达与 SA 含量没有相关性，但与病原体感染成正比激活。我们得出结论，SA 和 JA 途径在杨树中相互作用，导致类黄酮植物抗毒素的积累。
