Role of glutathione in potato response to French marigold essential oil

Abstract

Volatile organic compounds (VOCs) have a role in communication of plants with other organisms. The effect of VOCs from French marigold (Tagetes patula L.) essential oil (EO) on potato (Solanum tuberosum L.) plants was studied to examine the interaction between this ornamental plant species and potato as an important agricultural crop. According to comprehensive microarray analysis, EO affected the expression of numerous potato genes after 8 h of exposure. From 124 identified transcripts annotated to glutathione metabolism pathway in potato (sot00480), 43 were with significantly altered expression (35%), and 42 of them were up-regulated. Glutathione (GSH) is an essential low-molecular metabolite, which participates in the removal of reactive oxygen species (ROS), stress-generated signal molecules involved in immune responses. Transitions between glutathione reduced (GSH) and oxidized forms (GSSG) are finely controlled by complex enzymatic machinery. Thus, in order to examine in more details the role of glutathione in potato ROS balance after perception of VOCs, the expression of 10 selected genes involved in glutathione metabolism was further analysed by the qRT-PCR method. For this purpose potato plants were exposed to EO for 8 h during one or three consecutive days. Samples were collected immediately after EO removal, or after 5 and 10 days. Results showed that gene coding for γ-glutamylcysteine synthetase (γ-GCS), first in the line of GSH synthesis, had the highest level of expression after the first 8 h of exposure, indicating a fast response to VOCs perception. In other experimental groups synthesis of GSH, in which were involved GSH synthase (GSS) and glutamyltranspeptidase (GGT), was decreased. A similar pattern was observed for genes coding for enzymes involved in redox glutathione transduction (glutathione reductase - GR, isocitrate dehydrogenase - IDH, and dehydroascorbate reductase-like protein - DHAR). However, the highest alternation in expression between exposed potato and corresponding controls was observed for glutathione S-transferase (GST) genes, indicating that the glutathione-based response mechanism is an important component of ROS scavenging mechanisms in VOCs-induced responses of the potato. In addition, the potential of glutathione to sequester and detoxify exogenous VOCs by glutathione S-transferases, opens new research avenues.