Quinones are produced and sensed in all kingdoms of life1-4. Plants are primary producers of quinone1,2, but the role of quinone as a signalling agent in plants remains largely unknown. One well-documented role of quinone is in the induction of haustoria (specialized feeding structures) in plants that parasitize roots, which occurs in the presence of the host-derived quinone compound 2,6-dimethoxy-1,4-benzoquinone (DMBQ)5. However, how parasitic plants sense DMBQ remains unclear, as is whether nonparasitic plants are capable of sensing quinones. Here we use Arabidopsis thaliana and DMBQ as a model plant and quinone to show that DMBQ signalling occurs in Arabidopsis via elevation of cytosolic Ca2+ concentration. We performed a forward genetic screen in Arabidopsis that isolated DMBQ-unresponsive mutants, which we named cannot respond to DMBQ 1 (card1). The CANNOT RESPOND TO DMBQ 1 (CARD1; At5g49760, also known as HPCA1) gene encodes a leucine-rich-repeat receptor-like kinase that is highly conserved in land plants. In Arabidopsis, DMBQ triggers defence-related gene expression, and card1 mutants show impaired immunity against bacterial pathogens. In Phtheirospermum japonicum (a plant that parasitizes roots), DMBQ initiates Ca2+ signalling in the root and is important for the development of the haustorium. Furthermore, CARD1 homologues from this parasitic plant complement DMBQ-induced elevation of cytosolic Ca2+ concentration in the card1 mutant. Our results demonstrate that plants-unlike animals and bacteria-use leucine-rich-repeat receptor-like kinases for quinone signalling. This work provides insights into the role of quinone signalling and CARD1 functions in plants that help us to better understand the signalling pathways used during the formation of the haustorium in parasitic plants and in plant immunity in nonparasitic plants.

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通过富含亮氨酸的重复受体样激酶在植物中感知醌

醌类在生命的所有王国中产生和感知1-4。植物是醌 1,2 的主要生产者，但醌在植物中作为信号剂的作用在很大程度上仍然未知。醌的一个有据可查的作用是在寄生于根的植物中诱导吸器（特殊的进食结构），这种作用发生在宿主衍生的醌化合物 2,6-二甲氧基-1,4-苯醌 (DMBQ) 存在下5. 然而，寄生植物如何感知 DMBQ 仍不清楚，非寄生植物是否能够感知醌。在这里，我们使用拟南芥和 DMBQ 作为模型植物和醌来表明 DMBQ 信号通过细胞溶质 Ca2+ 浓度的升高在拟南芥中发生。我们在拟南芥中进行了正向遗传筛选，分离出 DMBQ 无反应的突变体，我们命名的不能响应 DMBQ 1 (card1)。无法响应 DMBQ 1（CARD1；At5g49760，也称为 HPCA1）基因编码一种富含亮氨酸的重复受体样激酶，在陆生植物中高度保守。在拟南芥中，DMBQ 触发防御相关基因表达，card1 突变体显示对细菌病原体的免疫力受损。在 Phtheirospermum japonicum（一种寄生于根的植物）中，DMBQ 在根中启动 Ca2+ 信号传导，对吸器的发育很重要。此外，来自这种寄生植物的 CARD1 同源物补充了 DMBQ 诱导的 card1 突变体中细胞溶质 Ca2+ 浓度的升高。我们的结果表明，与动物和细菌不同的植物使用富含亮氨酸的重复受体样激酶进行醌信号传导。