The systemin receptor SYR1 enhances resistance of tomato against herbivorous insects

The discovery in tomato of systemin (系统素), the first plant peptide hormone, was a fundamental change for the concept of plant hormones. Numerous other peptides have since been shown to play regulatory roles in many aspects of the plant life, including growth, development, fertilization and interactions with symbiotic organisms (共生生物). Systemin, an 18 amino acid peptide derived from a larger precursor protein, was proposed to act as the spreading signal that triggers systemic defence responses observed in plants after wounding or attack by herbivores (食草动物). Further work culminated (达到极点) in the identification of a leucine-rich repeat receptor kinase (LRR-RK) as the systemin receptor 160 (SR160). SR160 is a tomato homologue of Brassinosteroid Insensitive 1 (BRI1), which mediates the regulation of growth and development in response to the steroid hormone (甾体激素) brassinolide (油菜素内酯). However, a role of SR160/BRI1 as systemin receptor could not be corroborated (证实) by others. Here, we demonstrate that perception of systemin depends on a pair of distinct LRR-RKs termed SYR1 and SYR2. SYR1 acts as a genuine systemin receptor that binds systemin with high affinity and specificity. Further, we show that presence of SYR1, although not decisive (决定性的) for local and systemic wound responses, is important for defence against insect herbivory (取食).

西红柿系统素是第一个被发现的植物多肽激素，该激素的发现更新了植物激素概念。自从该激素的发现以来，人们又发现了许许多多的植物多肽类激素，在植物生活史的多个方面发挥作用，包括生长、发育、授精以及植物与共生生物间的互作。系统素，是一个具有18个氨基酸的多肽，其来自于一个更大的前体蛋白。系统素被认为在植物受到损伤或是食草动物攻击后扮演着传递信号的角色以诱导系统的防御反应。进一步的工作表明一个亮氨酸重复受体激酶LRR-RK是系统素受体SR160。SR160是BRI1的同源蛋白，BRI1介导植物响应于甾体激素油菜素内酯对于生长、发育的调控。然而，SR160/BRI1作为系统素受体的研究并未有人证实。本文报道了系统素的感知主要依赖于一对LRR-RK同源基因，即SYR1和SYR2。其中，SYR1作为主要的系统素受体，该蛋白与系统素具有高度亲和并且特异的结合能力。此外，作者显示SYR1尽管对于局部和系统的伤口响应并不是决定性的，但其对于植物抵抗昆虫取食具有非常重要的作用。

通讯：Georg Felix (http://www.zmbp.uni-tuebingen.de/plant-biochem/research-groups/felix.html)

doi: 10.1038/s41477-018-0106-0