Geranyl geranyl pyrophosphate synthase (GGPPS) is known to form an integral subunit of the heteromeric GPPS (geranyl pyrophosphate synthase) complex and catalyzes the biosynthesis of monoterpene in plants. Picrorhiza kurrooa Royle ex Benth., a medicinally important high altitude plant is known for picroside biomolecules, the monoterpenoids. However, the significance of heteromeric GPPS in P. kurrooa still remains obscure. Here, transient silencing of PkGGPPS was observed to reduce picroside-I (P-I) content by more than 60% as well as picroside-II (P-II) by more than 75%. Thus, PkGGPPS was found to be involved in the biosynthesis of P-I and P-II besides other terpenoids. To unravel the mechanism, small subunit of GPPS (PkGPPS.SSU) was identified from P. kurrooa. Protein-protein interaction studies in yeast as well as bimolecular fluorescence complementation (BiFC) in planta have indicated that large subunit of GPPS PkGPPS.LSUs (PkGGPPS1 and PkGGPPS2) and PkGPPS.SSU form a heteromeric GPPS. Presence of similar conserved domains such as light responsive motifs, low temperature responsive elements (LTRE), dehydration responsive elements (DREs), W Box and MeJA responsive elements in the promoters of PkGPPS.LSU and PkGPPS.SSU documented their involvement in picroside biosynthesis. Further, the tissue specific transcript expression analysis vis-à-vis epigenetic regulation (DNA methylation) of promoters as well as coding regions of PkGPPS.LSU and PkGPPS.SSU has strongly suggested their role in picroside biosynthesis. Taken together, the newly identified PkGPPS.SSU formed the heteromeric GPPS by interacting with PkGPPS.LSUs to synthesize P-I and P-II in P. kurrooa.

众所周知，香叶基香叶基焦磷酸合酶（GGPPS）形成异源GPPS（香叶基焦磷酸合酶）复合物的组成亚基，并催化植物中单萜的生物合成。Picrorhiza kurrooa Royle ex Benth。是一种医学上重要的高海拔植物，因其苦瓜苷类生物分子（单萜类化合物）而闻名。但是，异聚体GPPS在库氏疟原虫中的重要性仍然不清楚。这里，瞬时沉默PkGGPPS观察由超过60％，以减少胡黄连苷-I（PI）的含量以及胡黄连苷-II（P-II）由75％以上。因此，发现PkGGPPS除其他萜类化合物外还参与PI和P-II的生物合成。为了阐明该机制，请使用GPPS的小子单元（PkGPPS.SSU）是从红假单胞菌中鉴定的。酵母中的蛋白质相互作用和植物中的双分子荧光互补（BiFC）研究表明GPPS Pk GPPS.LSUs（Pk GGPPS1和Pk GGPPS2）和Pk GPPS.SSU的大亚基形成了异聚GPPS。PkGPPS.LSU和PkGPPS.SSU启动子中存在类似的保守域，例如光响应性基序，低温响应性元件（LTRE），脱水响应性元件（DRE），W Box和MeJA响应性元件记录了他们参与苦味甙生物合成的过程。此外，针对启动子的表观遗传调控（DNA甲基化）以及PkGPPS.LSU和PkGPPS.SSU的编码区的组织特异性转录物表达分析强烈表明了它们在苦瓜苷生物合成中的作用。综上所述，新鉴定的PkGPPS.SSU通过与Pk GPPS.LSUs相互作用，在库氏假单胞菌中合成PI和P-II，形成了异聚体GPPS 。