Phytochemistry and Phytopharmacology Division, Tropical Botanic Garden and Research Institute, Pacha-Palode, Thiruvananthapuram 695 562, Kerala, India.
J Exp Bot. 2011 Nov;62(15):5429-36. doi: 10.1093/jxb/err219. Epub 2011 Aug 23.
Prey capture and digestion in Nepenthes spp. through their leaf-evolved biological traps involve a sequence of exciting events. Sugar-rich nectar, aroma chemicals, narcotic alkaloid secretions, slippery wax crystals, and other biochemicals take part in attracting, capturing, and digesting preys in Nepenthes pitchers. Here we report the distribution of three potent naphthoquinones in Nepenthes khasiana and their roles in prey capture. Plumbagin was first detected in N. khasiana, and its content (root: 1.33 ± 0.02%, dry wt.) was the highest found in any natural source. Chitin induction enhanced plumbagin levels in N. khasiana (root: 2.17 ± 0.02%, dry wt.). Potted N. khasiana plants with limited growth of roots and aerial parts, showed higher levels of plumbagin accumulation (root: 1.92 ± 0.02%; root, chitin induction: 3.30 ± 0.21%, dry wt.) compared with field plants. Plumbagin, a known toxin, insect ecdysis inhibitor, and antimicrobial, was also found embedded in the waxy layers at the top prey capture region of N. khasiana pitchers. Chitin induction, mimicking prey capture, produced droserone and 5-O-methyl droserone in N. khasiana pitcher fluid. Both these naphthoquinone derivatives provide antimicrobial protection to the pitcher fluid from visiting preys. A two-way barrier was found between plumbagin and its two derivatives. Plumbagin was never detected in the pitcher fluid whereas both its derivatives were only found in the pitcher fluid on chitin induction or prey capture. The three naphthoquinones, plumbagin, droserone, and 5-O-methyl droserone, act as molecular triggers in prey capture and digestion in the carnivorous plant, N. khasiana.
猪笼草通过其进化而来的生物陷阱来捕获和消化猎物，这其中涉及一系列令人兴奋的事件。富含糖分的花蜜、香气化学物质、麻醉生物碱分泌物、滑溜的蜡晶以及其他生化物质参与吸引、捕捉和消化猪笼草瓶中的猎物。在这里，我们报告了三种强效萘醌在猪笼草中的分布及其在猎物捕获中的作用。我们首次在猪笼草中检测到了白花丹醌，其含量（根：1.33±0.02%，干重）在任何天然来源中都是最高的。几丁质诱导增强了猪笼草中白花丹醌的含量（根：2.17±0.02%，干重）。与野外植物相比，根部和地上部分生长受限的盆栽猪笼草植物中白花丹醌的积累水平更高（根：1.92±0.02%；根，几丁质诱导：3.30±0.21%，干重）。白花丹醌是一种已知的毒素、昆虫蜕皮抑制剂和抗菌剂，也被发现嵌入猪笼草瓶状叶顶部的蜡质层中，该部位是猎物的主要捕获区。几丁质诱导，模拟猎物捕获，在猪笼草瓶状叶液中产生了卓酮和 5-O-甲基卓酮。这两种萘醌衍生物为瓶状叶液提供了对来访猎物的抗菌保护。我们发现了一个双向屏障，将白花丹醌与其两种衍生物隔开。在瓶状叶液中从未检测到白花丹醌，而只有在几丁质诱导或猎物捕获时，才能在瓶状叶液中检测到这两种衍生物。这三种萘醌，白花丹醌、卓酮和 5-O-甲基卓酮，在食虫植物猪笼草的猎物捕获和消化中充当分子触发物。
