ROS and RNS Alterations in the Digestive Fluid of Nepenthes × ventrata Trap at Different Developmental Stages

Abstract

The carnivorous pitcher plant, Nepenthes x ventrata (Hort. ex Fleming = N. ventricosa Blanco x N. alata Blanco), produces passive traps containing digestive fluid. Although reactive oxygen species (ROS) in the fluid were detected in some pitcher plants, the participation of reactive nitrogen species (RNS) in the digestion process has not yet been examined. The aim of this work was to investigate the production of superoxide anion (O2•−), nitric oxide (NO) and peroxynitrite (ONOO−) levels in the digestive fluid of traps throughout organ development. We revealed the ROS and RNS occurrence in the digestive fluid, linked to the ROS-scavenging capacity and total phenolics content. In digestive fluid from the fed traps, NO emission was higher than in the fluid from the developed unfed pitcher. The concentration of nitrite (NO2−) decreased in the fluid from the fed traps in comparison to the unfed ones, pointing at NO2− as the key source of NO. The enhanced emission of NO was associated with lowered content of ONOO− in the fluid, probably due to lower production of O2•−. At the same time, despite a decline in total phenolics, the maximum ROS scavenging capacity was detected. In addition, ROS and RNS were noted even in closed traps, suggesting their involvement not only in digestion per se but also their action as signaling agents in trap ontogeny.

Is the Phytotoxic Effect of Digestive Fluid of Nepenthes x ventrata on Tomato Related to Reactive Oxygen Species?

“…Other compounds, isolated from carnivorous plants, may show a toxic effect; these include two naphthoquinones, droserone and its derivative 5-O-methyldroserone, which have beem found in the digestive fluid of N. khasiana [ 10 ] or 7-methyl-juglone isolated from N. alata [ 11 ]. Previous reports from our laboratory indicated the presence of phenolic compounds in the digestive fluid, the total content of which increased in fed traps [ 15 ]. Phenolics are regarded as strong allelochemicals of various modes of action in acceptor plants [ 26 ].…”

“…It may be proposed that compounds in the fluids from N. ventrata traps do not impact ROS production. Although investigations of the activity of enzymes of the antioxidant system are still required, the presence of ROS and reactive nitrogen species in the digestion liquid of these plants has been recently revealed [ 15 ].…”

“…The digestive fluid of the Nepenthes species is rich in mineral nutrient composition (boron, calcium, copper, iron and nickel) and anions Cl − , Br − and SO 4 2− [ 11 ]. Prey digestion (feeding process) is accompanied by alteration in fluid composition, including reactive oxygen species (ROS) and reactive nitrogen species (RNS) levels [ 15 ].…”

Do Reactive Oxygen and Nitrogen Species Have a Similar Effect on Digestive Processes in Carnivorous Nepenthes Plants and Humans?

“…In the N. ventrata Hort. ex Fleming digestive fluid, the presence of O2 •− was confirmed during the whole ontogeny of the trap, starting from the closed organs [44]. The authors proposed that radical forms of ROS are involved not only in the digestion per se but also play a role as compounds regulating the trap microbiome, although this needs further investigation.…”

“…Young traps with closed lids and visually aged traps have a higher pH in the digestive fluid. Low pH in the digestive fluid is probably linked to the elimination of excess microorganisms and potentially harmful pathogens originated from the prey [44]. The digestion in the pitcher trap is probably highly dependent on the pH of the digestive fluid and the trap age.…”