Enfissi Eugenia M A, Nogueira Marilise, Bramley Peter M, Fraser Paul D
School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 OEX, UK.
Plant J. 2017 Feb;89(4):774-788. doi: 10.1111/tpj.13428. Epub 2017 Feb 7.
Carotenoid biosynthesis in plants includes a complex series of desaturation/isomerisation reactions, catalyzed by four independent enzymes. In bacteria and fungi one desaturase/isomerase enzyme completes the same series of reactions. In the present study, a bacterial desaturase (crtI) from Pantoea ananatis has been overexpressed in the tangerine mutant of tomato (Solanum lycopersicon) which accumulates cis-carotene isomers in the fruit due to a defective isomerase (CRTISO) and the old gold crimson (og ) tomato mutant, which is defective in the fruit-enhanced lycopene β-cyclase (CYCB). Comprehensive molecular and biochemical characterization of the resulting lines expressing crtI has revealed negative feedback mechanisms, acting predominantly at the level of phytoene synthase-1 (PSY1), and feed-forward mechanisms inducing cyclisation. In both cases, altered transcription appears to be the progenitor, with subsequent post-transcriptional modulation highlighting the complexity of the processes involved in modulating carotenoid homeostasis in plant tissues.
植物中的类胡萝卜素生物合成包括一系列复杂的去饱和/异构化反应，由四种独立的酶催化。在细菌和真菌中，一种去饱和酶/异构酶就能完成相同的一系列反应。在本研究中，来自菠萝泛菌的一种细菌去饱和酶（crtI）在番茄（Solanum lycopersicon）的橙色突变体中过表达，该突变体由于异构酶（CRTISO）缺陷而在果实中积累顺式类胡萝卜素异构体，以及老金深红（og）番茄突变体，该突变体在果实增强的番茄红素β-环化酶（CYCB）方面存在缺陷。对表达crtI的所得株系进行的全面分子和生化表征揭示了负反馈机制，主要作用于八氢番茄红素合酶-1（PSY1）水平，以及诱导环化的前馈机制。在这两种情况下，转录改变似乎是起始因素，随后的转录后调节突出了植物组织中调节类胡萝卜素稳态所涉及过程 的复杂性。
