Biosynthesis of Phenylamide Phytoalexins in Pathogen-Infected Barley
Biosynthesis of Phenylamide Phytoalexins in Pathogen-Infected Barley
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DOI：
10.3390/ijms20225541
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发表时间：
2019-11-01
影响因子：
5.6
通讯作者：
Ishihara, Atsushi
中科院分区：
文献类型：
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作者：
Ube, Naoki;Yabuta, Yukinori;Ishihara, Atsushi
植物抗毒素是植物体内可诱导的抗菌代谢产物，在植物抗微生物感染中具有重要作用。HPLC分析检测了三种化合物1-3在被镰刀菌根腐病的病原体镰刀菌culmorum感染的大麦（Hordeum vulgare）根中的诱导积累。化合物1-3经光谱分析分别鉴定为9-羟基-8-氧色胺、8-氧色胺和（1H-吲哚-3-基）甲胺的肉桂酸酰胺。化合物1和2以前曾从小麦中报道过，而3是一个未描述的化合物。我们将1-3分别命名为麦酰胺A-C，因为它们是从属于小麦族的大麦和小麦中分离出来的。这些化合物具有抗菌活性，表明小麦酰胺在大麦中具有植物抗毒素的功能。给药氘标记的N-肉桂酰色胺（CinTry）大麦根导致有效的掺入CinTry到1和2，这表明它们是通过氧化CinTry合成的。通过数据库检索，在已知水稻THT基因序列的基础上，鉴定了9个THT编码基因（HvTHT 1-HvTHT 9）。由于HvTHT 7和HvTHT 8除了一个碱基之外具有相同的序列，我们通过RT-qPCR测量了它们的总表达水平。HvTHT 7/8在F.高潮HvTHT 7和HvTHT 8酶优选肉桂酰-和阿魏酰-CoA作为酰基供体，色胺作为酰基受体，并且（1H-吲哚-3-基）甲胺也被接受作为酰基受体。这些结果表明，HvTHT 7/8负责诱导小麦酰胺在大麦中的积累。
Phytoalexins are inducible antimicrobial metabolites in plants, and have been indicated to be important for the rejection of microbial infection. HPLC analysis detected the induced accumulation of three compounds 1-3 in barley (Hordeum vulgare) roots infected by Fusarium culmorum, the causal agent of Fusarium root rot. Compounds 1-3 were identified as cinnamic acid amides of 9-hydroxy-8-oxotryptamine, 8-oxotryptamine, and (1H-indol-3-yl)methylamine, respectively, by spectroscopic analysis. Compounds 1 and 2 had been previously reported from wheat, whereas 3 was an undescribed compound. We named 1-3 as triticamides A-C, respectively, because they were isolated from barley and wheat, which belong to the Triticeae tribe. These compounds showed antimicrobial activities, indicating that triticamides function as phytoalexins in barley. The administration of deuterium-labeled N-cinnamoyl tryptamine (CinTry) to barley roots resulted in the effective incorporation of CinTry into 1 and 2, which suggested that they were synthesized through the oxidation of CinTry. Nine putative tryptamine hydroxycinnamoyl transferase (THT)-encoding genes (HvTHT1-HvTHT9) were identified by database search on the basis of homology to known THT gene sequences from rice. Since HvTHT7 and HvTHT8 had the same sequences except one base, we measured their expression levels in total by RT-qPCR. HvTHT7/8 were markedly upregulated in response to infection by F. culmorum. The HvTHT7 and HvTHT8 enzymes preferred cinnamoyl- and feruloyl-CoAs as acyl donors and tryptamine as an acyl acceptor, and (1H-indol-3-yl)methylamine was also accepted as an acyl acceptor. These findings suggested that HvTHT7/8 are responsible for the induced accumulation of triticamides in barley.