Identification, functional characterization and developmental regulation of sesquiterpene synthases from sunflower capitate glandular trichomes

Background

Besides being essential for plant structure and metabolism, soluble carbohydrates play important roles in stress responses. Sucrose has been shown to confer to Arabidopsis seedlings a high level of tolerance to the herbicide atrazine, which causes reactive oxygen species (ROS) production and oxidative stress. The effects of atrazine and of exogenous sucrose on ROS patterns and ROS-scavenging systems were studied. Simultaneous analysis of ROS contents, expression of ROS-related genes and activities of ROS-scavenging enzymes gave an integrative view of physiological state and detoxifying potential under conditions of sensitivity or tolerance.

Results

Toxicity of atrazine could be related to inefficient activation of singlet oxygen (¹O₂) quenching pathways leading to ¹O₂ accumulation. Atrazine treatment also increased hydrogen peroxide (H₂O₂) content, while reducing gene expressions and enzymatic activities related to two major H₂O₂-detoxification pathways. Conversely, sucrose-protected plantlets in the presence of atrazine exhibited efficient ¹O₂ quenching, low ¹O₂ accumulation and active H₂O₂-detoxifying systems.

Conclusion

In conclusion, sucrose protection was in part due to activation of specific ROS scavenging systems with consequent reduction of oxidative damages. Importance of ROS combination and potential interferences of sucrose, xenobiotic and ROS signalling pathways are discussed.