Lei Wang1,2,3, Weining Cheng4, Jia Meng2,3,5, Mickey Speakmon6, Jiangping Qiu1, Suresh Pillai6, Keyan Zhu-Salzman2,3. 1. School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, People's Republic of China. 2. Department of Entomology, Texas A&M University, College Station, TX, USA. 3. Institute for Plant Genomics & Biotechnology, Texas A&M University, College Station, TX, USA. 4. Key Laboratory of Integrated Pest Management on Crops in Northwestern Loess Plateau, Ministry of Agriculture, Northwest A&F University, Yangling, People's Republic of China. 5. College of Plant Protection, Fujian Agricultural and Forest University, Fuzhou, People's Republic of China. 6. National Center for Electron Beam Research, Texas A&M University, College Station, TX, USA.
Abstract
BACKGROUND: Electron beam (eBeam) irradiation and hermetic storage are safe and effective technologies to protect stored products. Although hypoxic environment improves performance of some irradiated insects, whether hypoxia affects irradiation of storage insects and impacts pest control efficacy remains to be investigated. RESULTS: Using cowpea bruchid (Callosobruchus maculatus) larvae, we showed that, relative to eBeam irradiation under normoxia, the adult emergence rate increased substantially if they were exposed to hypoxia prior to and during eBeam treatment. Conversely, exposure to hypoxia only after eBeam irradiation did not have this protective effect. eBeam irradiation caused an increase in reactive oxygen species (ROS) in normoxic larvae but not in hypoxic larvae. The activity of citrate synthase, a pace-making enzyme in the citric acid cycle, was suppressed under hypoxia but resumed normal function within hours of reoxygenation, suggesting that reduced mitochondrial activity, and thus less ROS production under hypoxia increased insect tolerance to irradiation. Furthermore, reoxygenation accelerated eBeam-induced glutathione-S-transferase activation and potentiated eBeam-enhanced catalase activities. Faster and stronger detoxification capacity in eBeam-irradiated, hypoxic larvae may have protected them from oxidative damage. CONCLUSION: Hypoxic environment enhanced radiotolerance of bruchid larvae, presumably due to limited ROS production and elevated antioxidant enzymatic activities after reoxygenation.
BACKGROUND: Electron beam (eBeam) irradiation and hermetic storage are safe and effective technologies to protect stored products. Although hypoxic environment improves performance of some irradiated insects, whether hypoxia affects irradiation of storage insects and impacts pest control efficacy remains to be investigated. RESULTS: Using cowpea bruchid (Callosobruchus maculatus) larvae, we showed that, relative to eBeam irradiation under normoxia, the adult emergence rate increased substantially if they were exposed to hypoxia prior to and during eBeam treatment. Conversely, exposure to hypoxia only after eBeam irradiation did not have this protective effect. eBeam irradiation caused an increase in reactive oxygen species (ROS) in normoxic larvae but not in hypoxic larvae. The activity of citrate synthase, a pace-making enzyme in the citric acid cycle, was suppressed under hypoxia but resumed normal function within hours of reoxygenation, suggesting that reduced mitochondrial activity, and thus less ROS production under hypoxia increased insect tolerance to irradiation. Furthermore, reoxygenation accelerated eBeam-induced glutathione-S-transferase activation and potentiated eBeam-enhanced catalase activities. Faster and stronger detoxification capacity in eBeam-irradiated, hypoxic larvae may have protected them from oxidative damage. CONCLUSION: Hypoxic environment enhanced radiotolerance of bruchid larvae, presumably due to limited ROS production and elevated antioxidant enzymatic activities after reoxygenation.
Authors: Vanessa S Dias; Guy J Hallman; Olga Y Martínez-Barrera; Nick V Hurtado; Amanda A S Cardoso; Andrew G Parker; Luis A Caravantes; Camilo Rivera; Alexandre S Araújo; Florence Maxwell; Carlos E Cáceres-Barrios; Marc J B Vreysen; Scott W Myers Journal: Insects Date: 2020-06-15 Impact factor: 2.769