Hypoxic environment protects cowpea bruchid (Callosobruchus maculatus) from electron beam irradiation damage

Abstract

Hypoxic environment enhanced radiotolerance of bruchid larvae, presumably due to limited ROS production and elevated antioxidant enzymatic activities after reoxygenation. © 2018 Society of Chemical Industry.

Critical PO2 as a diagnostic biomarker for the effects of low‐oxygen modified and controlled atmospheres on phytosanitary irradiation treatments in the cabbage looper Trichoplusia ni (Hübner)

“…For example, in Drosophila melanogaster , resting adult metabolic rate is nearly constant between 21 and 3 kPa atmospheric PO 2 , then linearly decreases by approximately 10‐fold in comparison to normoxia, when oxygen levels are reduced from 3 and 0.1 kPa atmospheric PO 2. Reduced mitochondrial activity induced by hypoxia may produce fewer reactive oxygen species (ROS), and this has been hypothesized to increase insect tolerance to radiation . Meanwhile, hypoxia also induces increased antioxidant activity that may subsequently lower ROS levels and subsequently decrease oxidative damage .…”

“… Reduced mitochondrial activity induced by hypoxia may produce fewer reactive oxygen species (ROS), and this has been hypothesized to increase insect tolerance to radiation . Meanwhile, hypoxia also induces increased antioxidant activity that may subsequently lower ROS levels and subsequently decrease oxidative damage . Hypoxia also activates multiple downstream stress response signaling pathways such as heat shock proteins that have been shown to be up‐regulated when insects were exposed to ionizing radiation .…”

“…Modified atmosphere packaging also acts as an additional pest‐proofing layer preventing pests from re‐infesting a commodity after a phytosanitary treatment. However, this combination of phytosanitary irradiation with low‐oxygen modified atmosphere packaging is of concern to regulators because severe hypoxia (<1 kPa O 2 ) is known to increase insect radioprotective responses and decrease radiation‐induced mortality in a wide range of insects . For example, survival of the cabbage looper moth Trichoplusia ni (Hübner) was increased from 0% adult emergence when last‐instar caterpillars were irradiated at 100 Gy in normoxia (the partial pressure of O 2 in ambient normal air at sea level is 20.9 kPa) to more than 80% adult emergence when caterpillars were irradiated at the same dose in extreme hypoxia <0.1 kPa O 2 …”

Modified Atmosphere Does Not Reduce the Efficacy of Phytosanitary Irradiation Doses Recommended for Tephritid Fruit Flies

“…The replacement of atmospheric oxygen by flushing with nitrogen or certified gas mixtures has been applied in PI studies with dipterans, lepidopterans, and coleopterans, including the fruit fly species R. pomonella [18,[22][23][24]27,28,30]. In the fruit fly study, third instars maintained in a nitrogen rich atmosphere under severe hypoxic conditions before, during, and after irradiation showed decreased radiation sensitivity to a dose of 30 Gy compared with insects irradiated in air.…”

“…The concerns addressed by international plant protection and regulatory organizations regarding the application of PI under modified atmosphere are reasonable, considering the mechanisms underlying radiation sensitivity in several organisms. Insects pre-conditioned and irradiated under hypoxic or anoxic conditions may be protected against radiation damage by, among others, the reduction of reactive oxygen species (ROS) formation [16][17][18] and increased enzymatic antioxidant protection [19][20][21]. Tephritids, drosophilids, lepidopterans, and coleopterans irradiated with nonlethal doses of radiation, often below recommended phytosanitary irradiation doses, under reduced oxygen levels are less radiation sensitive than those irradiated in normoxia (21 kPa O 2 ) [18,[22][23][24][25][26][27][28][29][30].…”