Exploration and characterization of low-molecular compound that induces hypersensitive cell death in plants

超敏细胞死亡（HCD）是植物对病原菌侵染的一种典型抗病反应。虽然遗传学和生物化学研究已经确定了许多因素参与HCD的诱导，几乎所有这些都是蛋白质的因素，并很少有关注的低分子化学物质负责HCD。我们从烟草花叶病毒（TMV）侵染的烟草中分离到一种能在30 ℃（非HCD诱导温度）诱导HCD的低分子化合物，经理化分析鉴定为顺式冷杉醇（cis-abienol）。有趣的是，cis-abienol的化学结构与WAF-1的化学结构非常相似，WAF-1是一种二萜，最初被分离为烟草丝裂原活化蛋白激酶（MAPK）的激活剂WIPK，cis-abienol被发现诱导细胞死亡相关基因的表达以及WIPK和SIPK的激活，另一种烟草MAPK 1b阐明了cisabienol与这些MAPK的关系，我们产生了转基因烟草植物，其中WIPK和SIPK使用RNAi沉默。WIPK/SIPK RNAi植物表现出抑制HCD和改变茉莉酸和水杨酸的积累响应TMV感染或受伤。用顺式冷杉醇处理WIPK/SIPK RNAi植物削弱了TMV诱导的HCD。这些结果表明，顺式冷杉醇通过激活WIPK和SIPK参与TMV诱导的HCD。

Hypersensitive cell death (HCD) is a typical disease resistance response of plants against pathogen infection. Although genetical and biochemical studies have identified many factors involved in the induction of HCD, almost all of them are proteineous factors, and little has been focused on low-molecular chemicals responsible for HCD. We isolated a low-molecular compound that can induce HCD in tobacco mosaic virus (TMV)-infected tobacco at 30C, a non-permissive temperature for induction of HCD, and identified it as cis-abienol, a diterpene, by physicochemical analyses. Interestingly, the chemical structure of cis-abienol is very similar to that of WAF-1, a diterpene, which was originally isolated as an activator of the tobacco mitogen-activated protein kinase (MAPK) WIPK, cis-abienol was found to induce expression of cell death-related genes and activation of WIPK and SIPK, another tobacco MAPK lb clarify the relationship between cisabienol and these MAPKs, we generated transgenic tobacco plants in which WIPK and SIPK were silenced using RNAi. WIPK/SIPK RNAi plants exhibited inhibited HCD and altered accumulation of jasmonic and salicylic acids in response to infection with TMV or wounding. Treatment of WIPK/SIPK RNAi plants with cis-abienol compromised TMV-induced HCD. These results suggest that cis-abienol is involved in TMV-induced HCD via activation of WIPK and SIPK.