Department of Biophysics, Faculty of Science, Palacký University, Šlechtitelů 27, CZ-783 71, Olomouc, Czech Republic.
Ann Bot. 2022 Feb 11;129(3):357-365. doi: 10.1093/aob/mcab151.
The carnivorous pitcher plants of the genus Nepenthes have evolved modified leaves that act as pitcher traps. The traps are specialized for prey attraction, capture, digestion and nutrient uptake but not for photosynthetic assimilation.
In this study, we used antibodies against different photosynthetic (D1, Lhcb2, Lhcb4, RbcL) and respiratory-related (AOX, COXII) proteins for semi-quantification of these proteins in the assimilation part of the leaves and the pitcher traps of different Nepenthes species and hybrids. Different functional zones of the trap and the traps from different ontogenetic stages were investigated. The pitcher traps of the distantly related species Sarracenia purpurea ssp. venosa were used as an outgroup. In addition, chlorophyll fluorescence and infrared gas analysis were used for measurements of the net rate of photosynthesis (AN) and respiration in the dark (RD).
The pitcher traps contained the same or lower abundance of photosynthesis-related proteins in accordance with their low AN in comparison to the assimilation part of the leaves. Surprisingly, all traps contained a high amount of alternative oxidase (AOX) and low amount of cytochrome c oxidase subunit II (COX II) than in the assimilation part of the leaves. Thermal imaging did not confirm the role of AOX in pitcher thermogenesis.
The pitcher traps contain a high amount of AOX enzyme. The possible role of AOX in specialized pitcher tissue is discussed based on knowledge of the role and function of AOX in non-carnivorous plants. The roles of AOX in prey attraction, balance between light and dark reactions of photosynthesis, homeostasis of reactive oxygen species, digestive physiology and nutrient assimilation are discussed.
猪笼草属的肉食性猪笼草已经进化出了改良的叶子，这些叶子充当了猪笼陷阱。这些陷阱专门用于吸引、捕捉、消化和吸收猎物，但不能进行光合作用同化。
在这项研究中，我们使用了针对不同光合作用（D1、Lhcb2、Lhcb4、RbcL）和呼吸相关（AOX、COXII）蛋白的抗体，对半定量分析不同猪笼草物种和杂种的叶片同化部分和猪笼陷阱中的这些蛋白。我们研究了陷阱的不同功能区和不同个体发育阶段的陷阱。还使用了亲缘关系较远的瓶子草 Sarracenia purpurea ssp. venosa 的猪笼作为外群。此外，我们还使用叶绿素荧光和红外气体分析来测量暗呼吸（RD）和净光合作用速率（AN）。
与叶片同化部分相比，猪笼陷阱中的光合作用相关蛋白的丰度较低，这与它们较低的 AN 一致。令人惊讶的是，所有的陷阱都含有大量的替代氧化酶（AOX）和较少的细胞色素 c 氧化酶亚基 II（COX II），而这些在叶片同化部分中含量较低。热成像并没有证实 AOX 在猪笼热发生中的作用。
猪笼陷阱含有大量的 AOX 酶。根据非肉食性植物中 AOX 的作用和功能的知识，讨论了 AOX 在特殊猪笼组织中的可能作用。还讨论了 AOX 在猎物吸引、光合作用光和暗反应之间的平衡、活性氧物质的动态平衡、消化生理和养分吸收中的作用。
