A chalcone synthase with an unusual substrate preference is expressed in barley leaves in response to UV light and pathogen attack
A chalcone synthase with an unusual substrate preference is expressed in barley leaves in response to UV light and pathogen attack
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DOI：
10.1023/a:1006031822141
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发表时间：
1998-07-01
影响因子：
5.1
通讯作者：
Collinge, DB
中科院分区：
文献类型：
--
作者：
Christensen, AB;Gregersen, PL;Collinge, DB
利用差异杂交技术从接种大麦白粉病菌（Blumeria graminis f. sp. hordei，Bgh）的大麦叶片文库中分离到一个cDNA克隆。插入片段的开放阅读框（命名为HvCHS 2）编码与查耳酮脱氢酶（CHS）具有72-79%同一性且与芪脱氢酶具有65-68%同一性的多肽。HvCHS 2的氨基酸序列与柚皮素-CHS（EC 2.3.1.74）的共有序列的比对揭示了HvCHS 2和柚皮素-CHS之间的显著差异。HvCHS 2转录本在大麦叶片中强烈积累，以响应接种BGH，而只有微不足道的积累大麦柚皮素-CHS（CHS 1）转录本被视为接种后。HvCHS 2转录物的积累也由UV光引起。为了比较HvCHS 2与CHS 1的活性，在大肠杆菌中表达了这两种酶。HvCHS 2和CHS 1都催化查尔酮的形成。然而，HvCHS 2和CHS 1在它们的底物要求上不同。CHS 1以相当的速率使用肉桂酰-CoA和4-香豆酰-CoA，而阿魏酰-CoA是该酶的不良底物。相反，HvCHS 2以最高速率转化阿魏酰-CoA和咖啡酰-CoA，而肉桂酰-CoA是较差的底物。因此，HvCHS 2是一种新的病原体，紫外光诱导高圣草酚/圣草酚CHS参与直接生产具有多取代B环的黄酮类化合物。
A cDNA clone was isolated by differential hybridization from a library prepared from barley leaves inoculated with the fungus Blumeria graminis f.sp. hordei (Bgh). The open reading frame of the insert (designated HvCHS2) encoded a polypeptide with 72-79% identity to chalcone synthases (CHS) and 65-68% identity to stilbene synthases. Alignments of the amino acid sequence of HvCHS2 with the consensus sequence of naringenin-CHS (EC 2.3.1.74) reveals significant differences between HvCHS2 and naringenin-CHS. HvCHS2 transcripts accumulate strongly in barley leaves in response to inoculation with Bgh, whereas only insignificant accumulation of barley naringenin-CHS (CHS1) transcripts is seen upon the inoculation. The accumulation of HvCHS2 transcripts is also elicited by UV light. To compare the activity of HvCHS2 with the activity of CHS1, the two enzymes were expressed in Escherichia coli. Both HvCHS2 and CHS1 catalyse the formation of chalcones. However, HvCHS2 and CHS1 differ in their substrate requirements. CHS1 uses cinnamoyl-CoA and 4-coumaroyl-CoA at comparable rates whereas feruloyl-CoA is a poor substrate for this enzyme. In contrast, HvCHS2 converts feruloyl-CoA and caffeoyl-CoA at the highest rate whereas cinnamoyl-CoA is a poor substrate. Thus, HvCHS2 is a novel pathogen and UV light induces homoeriodictyol/eriodictyol CHS involved in the direct production of flavonoids possessing multi-substituted B-rings.