Alkylresorcinol Synthases Expressed in Sorghum bicolor Root Hairs Play an Essential Role in the Biosynthesis of the Allelopathic Benzoquinone Sorgoleone
Alkylresorcinol Synthases Expressed in Sorghum bicolor Root Hairs Play an Essential Role in the Biosynthesis of the Allelopathic Benzoquinone Sorgoleone
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DOI：
10.1105/tpc.109.072397
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发表时间：
2010-03-01
期刊：
影响因子：
11.6
通讯作者：
Baerson, Scott R.
中科院分区：
文献类型：
--
作者：
Cook, Daniel;Rimando, Agnes M.;Baerson, Scott R.
高粱被认为是一种化感作用作物物种，产生植物毒素，例如脂质苯醌高粱酮，这可能解释了高粱属植物的许多化感作用特性。目前的证据表明，sorgoleone 生物合成仅发生在根毛细胞中，并涉及从不寻常的 16:3 Delta(9,12,15) 脂肪酰基辅酶 A 起始单元衍生的烷基间苯二酚中间体（5-[(Z,Z)-8',11',14'-十五碳三烯基]间苯二酚）的产生。这导致有人提出涉及一种或多种烷基间苯二酚合酶（ARS）、III型聚酮化合物合酶（PKS），其使用中长链脂肪酰基辅酶A起始单元通过与丙二酰辅酶A反复缩合产生5-烷基间苯二酚。为了表征负责十五烷基间苯二酚中间体生物合成的酶，首先从分离的 S. bicolor（基因型 BTx623）根毛制备的先前描述的表达序列标签数据库中挖掘所有 PKS 样序列。定量实时 RT-PCR 分析显示，其中三个序列优先在根毛中表达，其中两个（称为 ARS1 和 ARS2）在重组酶研究中被发现编码能够接受各种脂肪酰基辅酶 A 起始单元的 ARS 酶。此外，针对 ARS1 和 ARS2 的 RNA 干扰实验导致产生多个独立的转化体事件，表现出 sorgoleone 水平显着降低。因此，ARS1 和 ARS2 都可能参与植物中 sorgoleone 的生物合成。 ARS1 和 ARS2 的序列还用于鉴定编码 ARS 的几种水稻 (Oryza sativa) 基因，这些基因可能参与防御相关烷基间苯二酚的生产。
Sorghum bicolor is considered to be an allelopathic crop species, producing phytotoxins such as the lipid benzoquinone sorgoleone, which likely accounts for many of the allelopathic properties of Sorghum spp. Current evidence suggests that sorgoleone biosynthesis occurs exclusively in root hair cells and involves the production of an alkylresorcinolic intermediate (5-[(Z, Z)-8',11',14'-pentadecatrienyl]resorcinol) derived from an unusual 16:3 Delta(9,12,15) fatty acyl-CoA starter unit. This led to the suggestion of the involvement of one or more alkylresorcinol synthases (ARSs), type III polyketide synthases (PKSs) that produce 5-alkylresorcinols using medium to long-chain fatty acyl-CoA starter units via iterative condensations with malonyl-CoA. In an effort to characterize the enzymes responsible for the biosynthesis of the pentadecyl resorcinol intermediate, a previously described expressed sequence tag database prepared from isolated S. bicolor (genotype BTx623) root hairs was first mined for all PKS-like sequences. Quantitative real-time RT-PCR analyses revealed that three of these sequences were preferentially expressed in root hairs, two of which (designated ARS1 and ARS2) were found to encode ARS enzymes capable of accepting a variety of fatty acyl-CoA starter units in recombinant enzyme studies. Furthermore, RNA interference experiments directed against ARS1 and ARS2 resulted in the generation of multiple independent transformant events exhibiting dramatically reduced sorgoleone levels. Thus, both ARS1 and ARS2 are likely to participate in the biosynthesis of sorgoleone in planta. The sequences of ARS1 and ARS2 were also used to identify several rice (Oryza sativa) genes encoding ARSs, which are likely involved in the production of defense-related alkylresorcinols.