Vacuole-Localized Berberine Bridge Enzyme-Like Proteins Are Required for a Late Step of Nicotine Biosynthesis in Tobacco
Vacuole-Localized Berberine Bridge Enzyme-Like Proteins Are Required for a Late Step of Nicotine Biosynthesis in Tobacco
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DOI：
10.1104/pp.110.170878
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发表时间：
2011-04-01
期刊：
影响因子：
7.4
通讯作者：
Hashimoto, Takashi
中科院分区：
文献类型：
--
作者：
Kajikawa, Masataka;Shoji, Tsubasa;Hashimoto, Takashi
烟草（Nicotiana tabacum）植物在其根部合成尼古丁和相关的吡啶类生物碱，如新烟草碱，并将其积累在其地上部分作为对食草动物的化学防御。除草剂诱导的茉莉酸信号通过尼古丁（NIC）调节位点激活尼古丁生物合成和转运的结构基因。烟草生物碱的生物合成涉及一种未鉴定的烟酸衍生代谢物与N-甲基吡咯啉鎓阳离子或与其本身的缩合，但确切的酶促反应和所涉及的酶仍不清楚。在这里，我们报告，茉莉酸诱导烟草基因编码的黄连素桥酶家族（BBLs）的黄素氧化酶在根中表达和NIC位点的调节。当BBL基因在烟草毛状根或烟草植物中的表达被抑制时，尼古丁的产生大大减少，并逐渐积累一种新的尼古丁代谢产物二氢甲烟碱。在茉莉酸诱导的培养烟草细胞中，抑制BBL表达有效地抑制了新烟草碱和其他吡啶生物碱的形成。绿色荧光蛋白标记的BBL的亚细胞分级和定位显示BBL定位于液泡中。这些结果表明，BBL参与了烟草生物碱生物合成中吡啶环缩合反应之后的后期氧化步骤。
Tobacco (Nicotiana tabacum) plants synthesize nicotine and related pyridine-type alkaloids, such as anatabine, in their roots and accumulate them in their aerial parts as chemical defenses against herbivores. Herbivory-induced jasmonate signaling activates structural genes for nicotine biosynthesis and transport by way of the NICOTINE (NIC) regulatory loci. The biosynthesis of tobacco alkaloids involves the condensation of an unidentified nicotinic acid-derived metabolite with the N-methylpyrrolinium cation or with itself, but the exact enzymatic reactions and enzymes involved remain unclear. Here, we report that jasmonate-inducible tobacco genes encoding flavin-containing oxidases of the berberine bridge enzyme family (BBLs) are expressed in the roots and regulated by the NIC loci. When expression of the BBL genes was suppressed in tobacco hairy roots or in tobacco plants, nicotine production was highly reduced, with a gradual accumulation of a novel nicotine metabolite, dihydromethanicotine. In the jasmonate-elicited cultured tobacco cells, suppression of BBL expression efficiently inhibited the formation of anatabine and other pyridine alkaloids. Subcellular fractionation and localization of green fluorescent protein-tagged BBLs showed that BBLs are localized in the vacuoles. These results indicate that BBLs are involved in a late oxidation step subsequent to the pyridine ring condensation reaction in the biosynthesis of tobacco alkaloids.