Many plants emit diverse floral scents that mediate plant–environment interactions and attain reproductive success. However, how plants evolve novel and adaptive biosynthetic pathways for floral volatiles remains unclear. Here, we show that in the wild tobacco, Nicotiana attenuata, a dominant species-specific floral volatile (benzyl acetone, BA) that attracts pollinators and deters florivore is synthesized by phenylalanine ammonia-lyase 4 (NaPAL4), isoflavone reductase 3 (NaIFR3), and chalcone synthase 3 (NaCHAL3). Transient expression of NaFIR3 alone in N. attenuata leaves is sufficient and necessary for ectopic foliar BA emissions, and coexpressing NaIFR3 with NaPAL4 and NaCHAL3 increased the BA emission levels. Independent changes in transcription of NaPAL4 and NaCHAL3 contributed to intraspecific variations of floral BA emission. However, among species, the gain of expression of NaIFR3 resulted in the biosynthesis of BA, which was only found in N. attenuata. This study suggests that novel metabolic pathways associated with adaptation can arise via reconfigurations of gene expression.

中文翻译：

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野生烟草中新型和自适应花香的演变。

许多植物散发出不同的花香，它们介导植物与环境之间的相互作用并获得繁殖成功。然而，植物如何发展新的和适应性的花卉挥发物生物合成途径尚不清楚。在这里，我们表明，在野生型烟草，烟草attenuata，显性物种特异性花香挥发性（苄基丙酮，BA），吸引传粉和阻吓florivore由苯丙氨酸合成丙氨酸解氨酶4（NaPAL4），异黄酮还原酶3（NaIFR3）和查尔酮合酶3（NaCHAL3）。NaFIR3单独在淡色猪笼草叶片中的瞬时表达对于异位叶BA排放和共表达NaIFR3是足够和必要的与NaPAL4和NaCHAL3增加了BA排放水平。NaPAL4和NaCHAL3转录的独立变化有助于花卉BA发射的种内变异。然而，在物种中，NaIFR3表达的增加导致了BA的生物合成，而BA仅在淡色猪笼草中被发现。这项研究表明，与适应相关的新的代谢途径可以通过基因表达的重新配置而产生。