School of Life Sciences, Chongqing University, Chongqing, 401331, China; Center of Plant Functional Genomics, Institute of Advanced Interdisciplinary Studies, Chongqing University, Chongqing, 401331, China.
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, 100101, Beijing, China.
Metab Eng. 2022 Jul;72:188-199. doi: 10.1016/j.ymben.2022.03.007. Epub 2022 Mar 23.
Glandular trichomes, known as metabolic cell factories, have been proposed as highly suitable for metabolically engineering the production of plant high-value specialized metabolites. Natural pyrethrins, found only in Dalmatian pyrethrum (Tanacetum cinerariifolium), are insecticides with low mammalian toxicity and short environmental persistence. Type I pyrethrins are esters of the monoterpenoid trans-chrysanthemic acid with one of the three rethrolone-type alcohols. To test if glandular trichomes can be made to synthesize trans-chrysanthemic acid, we reconstructed its biosynthetic pathway in tomato type VI glandular trichomes, which produce large amounts of terpenoids that share the precursor dimethylallyl diphosphate (DMAPP) with this acid. This was achieved by coexpressing the trans-chrysanthemic acid pathway related genes including TcCDS encoding chrysanthemyl diphosphate synthase and the fusion gene of TcADH2 encoding the alcohol dehydrogenase 2 linked with TcALDH1 encoding the aldehyde dehydrogenase 1 under the control of a newly identified type VI glandular trichome-specific metallocarboxypeptidase inhibitor promoter. Whole tomato leaves harboring type VI glandular trichomes expressing all three aformentioned genes had a concentration of total trans-chrysanthemic acid that was about 1.5-fold higher (by mole number) than the levels of β-phellandrene, the dominant monoterpene present in non-transgenic leaves, while the levels of β-phellandrene and the representative sesquiterpene β-caryophyllene in transgenic leaves were reduced by 96% and 81%, respectively. These results suggest that the tomato type VI glandular trichome is an alternative platform for the biosynthesis of trans-chrysanthemic acid by metabolic engineering.
腺毛，被称为代谢细胞工厂，已被提议作为高度适合代谢工程植物高附加值的特殊代谢物的生产。天然除虫菊酯，仅存在于大丽花花除虫菊（Tanacetum cinerariifolium），是一种对哺乳动物毒性低、环境持久性短的杀虫剂。I 型除虫菊酯是顺式菊酸与三种瑞特隆醇型醇之一的酯。为了测试腺毛是否可以合成顺式菊酸，我们在番茄 VI 型腺毛中重建了其生物合成途径，该腺毛产生大量萜类化合物，与该酸共享前体二甲基烯丙基二磷酸（DMAPP）。这是通过共表达与顺式菊酸途径相关的基因来实现的，包括编码菊二磷酸合酶的 TcCDS 和编码与 TcALDH1 连接的醇脱氢酶 2 的融合基因 TcADH2，该基因受新鉴定的 VI 型腺毛特异性金属羧肽酶抑制剂启动子的控制。表达上述三种基因的全番茄叶中总顺式菊酸的浓度比非转基因叶中主要单萜 β-水芹烯的浓度高约 1.5 倍（按摩尔数计），而转基因叶中 β-水芹烯和代表性倍半萜 β-石竹烯的浓度分别降低了 96%和 81%。这些结果表明，番茄 VI 型腺毛是通过代谢工程合成顺式菊酸的替代平台。
