PNAS：植物免疫信号水杨酸生物合成的时空调控

摘要 : 水杨酸（SA）是一种重要的免疫信号，能够启动植物的抗病防御。水杨酸生物合成一般是病原体诱导的，但人们并不清楚这一过程受到怎样的调控。杜克大学的研究团队通过研究拟南芥填补了这方面的空白。

水杨酸(SA)是一种重要的免疫信号，能够启动植物的抗病防御。水杨酸生物合成一般是病原体诱导的，但人们并不清楚这一过程受到怎样的调控。

杜克大学的研究团队通过研究拟南芥填补了这方面的空白，揭示了水杨酸生物合成在时间和空间上的调控机制。这项研究发表在七月二日的美国国家科学院院刊PNAS杂志上，文章通讯作者是著名华人女科学家董欣年(Xinnian Dong)教授。

董欣年教授早年毕业于武汉大学，在哈佛大学完成博士后研究，2012年当选为美国国家科学院院士。主要研究水杨酸和茉莉酸介导的信号转导途径及其相互作用机制。

植物受病原体感染后，会获得一种持久广泛的抗性，即系统获得性抗性(SAR)。已知水杨酸在SAR和局部免疫防御中起到了关键性的作用。当拟南芥遭遇病原体时，关键的水杨酸合成酶基因ICS1被激活，提高了水杨酸的生物合成。

研究人员通过筛选鉴定了激活ICS1的两个转录因子：NTL9(NTM1-LIKE 9)和CHE(CCA1 HIKING EXPEDITION)。NTL9在形成气孔的保卫细胞中激活ICS1，帮助气孔快速关闭，阻止病原体进入。研究显示，NTL9介导的水杨酸合成是气孔免疫所必需的。

CHE是主要的生物钟振荡因子，介导水杨酸水平的节律性变化。此外，SAR过程也需要通过CHE提高系统性的水杨酸合成。

研究指出，水杨酸生物合成在时间和空间上受到多种转录因子的调控。这一发现填补了病原体识别和水杨酸生产之间的信号传导空白。

原文标题：Spatial and temporal regulation of biosynthesis of the plant immune signal salicylic acid

原文摘要：The plant hormone salicylic acid (SA) is essential for local defense and systemic acquired resistance (SAR). When plants, such as Arabidopsis, are challenged by different pathogens, an increase in SA biosynthesis generally occurs through transcriptional induction of the key synthetic enzyme isochorismate synthase 1 (ICS1). However, the regulatory mechanism for this induction is poorly understood. Using a yeast one-hybrid screen, we identified two transcription factors (TFs), NTM1-LIKE 9 (NTL9) and CCA1 HIKING EXPEDITION (CHE), as activators of ICS1 during specific immune responses. NTL9 is essential for inducing ICS1 and two other SA synthesis-related genes, PHYTOALEXIN-DEFICIENT 4 (PAD4) and ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1), in guard cells that form stomata. Stomata can quickly close upon challenge to block pathogen entry. This stomatal immunity requires ICS1 and the SA signaling pathway. In the ntl9mutant, this response is defective and can be rescued by exogenous application of SA, indicating that NTL9-mediated SA synthesis is essential for stomatal immunity. CHE, the second identified TF, is a central circadian clock oscillator and is required not only for the daily oscillation in SA levels but also for the pathogen-induced SA synthesis in systemic tissues during SAR. CHE may also regulate ICS1 through the known transcription activators CALMODULIN BINDING PROTEIN 60g (CBP60g) and SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1) because induction of these TF genes is compromised in the che-2mutant. Our study shows that SA biosynthesis is regulated by multiple TFs in a spatial and temporal manner and therefore fills a gap in the signal transduction pathway between pathogen recognition and SA production.

作者：阳光森林

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