Discovery, Biosynthesis and Stress-Related Accumulation of Dolabradiene-Derived Defenses in Maize
Discovery, Biosynthesis and Stress-Related Accumulation of Dolabradiene-Derived Defenses in Maize
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DOI：
10.1104/pp.17.01351
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发表时间：
2018-04-01
期刊：
影响因子：
7.4
通讯作者：
Zerbe, Philipp
中科院分区：
文献类型：
--
作者：
Mafu, Sibongile;Ding, Yezhang;Zerbe, Philipp
萜类化合物是玉米(Zea Mays)化学防御的主要成分，它介导对食草动物、病原体和其他环境挑战的反应。在这里，我们描述了一类玉米二萜类化合物的生物合成和诱导生产，命名为dolabralexins。Dolabralexin的生物合成涉及两种二萜合成酶的顺序活性，即ENT-COPALYL-二磷酸合成酶(ZmAN2)和考拉烯合成酶-LIKE4(ZmKSL4)。ZmAN2和ZmKSL4共同形成二萜碳氢化合物多拉二烯。此外，我们还对细胞色素P450单加氧酶ZmCYP71Z16进行了生化表征，该酶催化多拉二烯氧化生成环氧化物15，16-环氧多拉宾和3-β-羟基-15，16-环氧多拉巴烯(环氧多拉巴烯)。在诱变条件下，Zman2突变体中不存在多拉二烯和环氧多拉巴酚，证实了ZmAN2的体内生物合成需求。结合质谱学和核磁共振实验证明，大部分环氧多拉布林进一步转化为3b，15，16-三羟基多拉宾(三羟基多拉宾)。大田种植的玉米根组织的代谢产物图谱表明，在普通玉米品种中广泛存在多拉布列辛的生物合成，其中三羟基多拉布烯是主要的二萜类化合物。氧化胁迫诱导根组织中Dolabralexin的积累和ZmAN2和ZmKSL4的转录表达，代谢产物和转录产物的积累在病原菌镰刀菌和禾谷镰刀菌的诱导下得到上调。环氧多拉巴酚在10微克毫升(-1)的浓度下对两种病原菌的生长均有显著的抑制作用，而三羟基多拉布林对黄萎病原菌的抑制作用是专一性的。这些发现表明，Dolabralexins在玉米逆境相互作用中具有防御相关的作用，并扩大了二萜类防御的已知化学空间，作为了解并最终提高玉米抗逆性的遗传靶标。
Terpenoids are a major component of maize (Zea mays) chemical defenses that mediate responses to herbivores, pathogens, and other environmental challenges. Here, we describe the biosynthesis and elicited production of a class of maize diterpenoids, named dolabralexins. Dolabralexin biosynthesis involves the sequential activity of two diterpene synthases, ENT-COPALYL DIPHOSPHATE SYNTHASE (ZmAN2) and KAURENE SYNTHASE-LIKE4 (ZmKSL4). Together, ZmAN2 and ZmKSL4 form the diterpene hydrocarbon dolabradiene. In addition, we biochemically characterized a cytochrome P450 monooxygenase, ZmCYP71Z16, which catalyzes the oxygenation of dolabradiene to yield the epoxides 15,16-epoxydolabrene (epoxydolabrene) and 3 beta-hydroxy-15,16-epoxydolabrene (epoxydolabranol). The absence of dolabradiene and epoxydolabranol in Zman2 mutants under elicited conditions confirmed the in vivo biosynthetic requirement of ZmAN2. Combined mass spectrometry and NMR experiments demonstrated that much of the epoxydolabranol is further converted into 3b, 15,16-trihydroxydolabrene (trihydroxydolabrene). Metabolite profiling of field-grown maize root tissues indicated that dolabralexin biosynthesis is widespread across common maize cultivars, with trihydroxydolabrene as the predominant diterpenoid. Oxidative stress induced dolabralexin accumulation and transcript expression of ZmAN2 and ZmKSL4 in root tissues, and metabolite and transcript accumulation were up-regulated in response to elicitation with the fungal pathogens Fusarium verticillioides and Fusarium graminearum. Consistently, epoxydolabranol significantly inhibited the growth of both pathogens in vitro at 10 mu g mL(-1), while trihydroxydolabrene-mediated inhibition was specific to F. verticillioides. These findings suggest that dolabralexins have defense-related roles in maize stress interactions and expand the known chemical space of diterpenoid defenses as genetic targets for understanding and ultimately improving maize resilience.