Poutrain Pierre, Mazars Christian, Thiersault Martine, Rideau Marc, Pichon Olivier
Université François Rabelais de Tours, EA 2106 Biomolécules et Biotechnologies végétales, F-37200 Tours, France.
J Exp Bot. 2009;60(4):1387-98. doi: 10.1093/jxb/erp017. Epub 2009 Feb 13.
Calcium-mediated signalling is ubiquitous in both animals and plants. Changes in cytoplasmic free Ca(2+) concentration couple diverse arrays of stimuli to their specific responses, the specificity of the stimulus being determined by integrated actions between multiple Ca(2+) mobilization pathways. In this work, a pharmacological approach is reported, aimed at deciphering the role of calcium as a second messenger in the transduction pathway leading to the inhibitory effect of 2,4-dichlorophenoxyacetic acid (2,4-D), in regulating monoterpene indole alkaloid (MIA) biosynthesis in Catharanthus roseus cells. It is demonstrated here that auxin-dependent MIA biosynthesis is differentially regulated by two distinct calcium release components from internal stores in C. roseus showing pharmacological profiles similar to those displayed by animal RyR and IP3 channels. MIA biosynthesis is stimulated by caffeine (Ca(2+)-release activator through RyR channels) and by heparin and TMB8 (Ca(2+)-release inhibitors of IP3 channels) whereas MIA biosynthesis is inhibited by mastoparan (Ca(2+)-release activator of IP3 channels) and by ruthenium red and DHBP (Ca(2+)-release inhibitors of RyR channels). Furthermore, calcium, as 2,4-D, acts on MIA biosynthesis by regulating the monoterpene moiety of the MIA biosynthesis pathway since calcium channel modulators preferentially modulate g10h expression, the gene encoding the enzyme of the secoiridoid monoterpene pathway, that is the major target of 2,4-D action. In addition, the simultaneous use of caffeine (an activator of RyR channel in animals) and TMB8 (an inhibitor of the IP3 channel) in 2,4-D treated cells triggers a synergistic effect on MIA accumulation. This finding suggests an opposite and co-ordinated action of multiple Ca(2+)-release pathways in 2,4-D signal transduction, adding a new level of complexity to calcium signalling in plants and questioning the existence of RyR and IP3 channels in plants.
钙介导的信号传导在动物和植物中普遍存在。细胞质游离Ca(2+)浓度的变化将各种刺激与其特定反应联系起来，刺激的特异性由多种Ca(2+)动员途径之间的综合作用决定。在这项工作中，报道了一种药理学方法，旨在阐明钙作为第二信使在导致2,4-二氯苯氧乙酸（2,4-D）抑制作用的转导途径中的作用，该途径调节长春花细胞中单萜吲哚生物碱（MIA）的生物合成。本文证明，生长素依赖性MIA生物合成受到长春花中来自内部储存的两种不同钙释放成分的差异调节，其药理学特征与动物兰尼碱受体（RyR）和肌醇三磷酸（IP3）通道所显示的相似。MIA生物合成受到咖啡因（通过RyR通道的Ca(2+)释放激活剂）、肝素和8-(N,N-二甲基氨基)辛酯（TMB8，IP3通道的Ca(2+)释放抑制剂）的刺激，而MIA生物合成受到蜂毒素（IP3通道的Ca(2+)释放激活剂）、钌红和二氢吡啶（DHBP，RyR通道的Ca(2+)释放抑制剂）的抑制。此外，钙与2,4-D一样，通过调节MIA生物合成途径的单萜部分来作用于MIA生物合成，因为钙通道调节剂优先调节g10h的表达，g10h是编码裂环烯醚萜单萜途径中酶的基因，是2,4-D作用的主要靶点。此外，在2,4-D处理的细胞中同时使用咖啡因（动物中RyR通道的激活剂）和TMB8（IP3通道的抑制剂）会对MIA积累产生协同作用。这一发现表明，多种Ca(2+)释放途径在2,4-D信号转导中具有相反且协调的作用，为植物中的钙信号传导增加了新的复杂程度，并对植物中RyR和IP3通道的存在提出了质疑。
