In the wild tomato Solanum habrochaites, the Sst2 locus on chromosome 8 is responsible for the biosynthesis of several class II sesquiterpene olefins by glandular trichomes. Analysis of a trichome-specific EST collection from S. habrochaites revealed two candidate genes for the synthesis of Sst2-associated sesquiterpenes. zFPS encodes a protein with homology to Z-isoprenyl pyrophosphate synthases and SBS (for Santalene and Bergamotene Synthase) encodes a terpene synthase with homology to kaurene synthases. Both genes were found to cosegregate with the Sst2 locus. Recombinant zFPS protein catalyzed the synthesis of Z,Z-FPP from isopentenylpyrophosphate (IPP) and dimethylallylpyrophosphate (DMAPP), while coincubation of zFPS and SBS with the same substrates yielded a mixture of olefins identical to the Sst2-associated sesquiterpenes, including (+)-α-santalene, (+)-endo-β-bergamotene, and (−)-endo-α-bergamotene. In addition, headspace analysis of tobacco (Nicotiana sylvestris) plants expressing zFPS and SBS in glandular trichomes afforded the same mix of sesquiterpenes. Each of these proteins contains a putative plastid targeting sequence that mediates transport of a fused green fluorescent protein to the chloroplasts, suggesting that the biosynthesis of these sesquiterpenes uses IPP and DMAPP from the plastidic DXP pathway. These results provide novel insights into sesquiterpene biosynthesis and have general implications concerning sesquiterpene engineering in plants.
在野生番茄Solanum habrochaites中,第8号染色体上的Sst2基因座负责腺毛中多种II类倍半萜烯烃的生物合成。从S. habrochaites的腺毛特异性EST集合中分析发现,有两个候选基因可以合成Sst2相关的倍半萜烯烃。zFPS编码一个与Z-异戊二烯基焦磷酸合成酶同源的蛋白质,而SBS(Santalene和Bergamotene Synthase)编码一个与矮秆素合成酶同源的萜烯合成酶。这两个基因被发现与Sst2基因座共同分离。重组zFPS蛋白质催化从异戊基焦磷酸酯(IPP)和二甲基烯丙基焦磷酸酯(DMAPP)合成Z,Z-FPP,而将zFPS和SBS与相同底物共同孵育则产生与Sst2相关的倍半萜烯烃相同的烯烃混合物,包括(+)-α-矢车菊烯、(+)-内-β-佛手柑烯和(-)-内-α-佛手柑烯。此外,表达zFPS和SBS的腺毛中的烟草(Nicotiana sylvestris)植物的空气中也产生了相同的倍半萜烯烃混合物。这些蛋白质中的每一个都包含一个推测的质体定位序列,该序列介导了融合绿色荧光蛋白到叶绿体的转运,表明这些倍半萜烯烃的生物合成使用来自质体DXP途径的IPP和DMAPP。这些结果为倍半萜烯烃的生物合成提供了新的见解,并具有关于植物倍半萜烯烃工程的普遍意义。