Cold hardiness in Ostrinia nubilalis (Lepidoptera: Pyralidae): Glycerol content, hexose monophosphate shunt activity, and antioxidative defense system

Abstract

Abstract. Many insects in temperate regions overwinter in diapause, during which they are cold hardy. In these insects, one of the metabolic adaptations to the unfavorable environmental conditions is the synthesis of cryoprotectants/anhydroprotectants. The aim of this study was to investigate the connection between the antioxidative system and synthesis of cryoprotectants (mainly glycerol) in diapausing larvae of the European corn borer, Ostrinia nubilalis (Lepidoptera: Pyralidae). At two periods during diapause (November and February), in three groups of insects (kept under field conditions; -12°C for two weeks; 8°C for two weeks), the activity of key enzymes of the antioxidative system and oxidative part of the hexose monophosphate shunt were measured: superoxide dismutase, catalase, non selenium glutathione peroxidase, glutathione S-transferase, glutathione reductase, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, as well that of the antioxidative components: total glutathione and ascorbate, and dehydroascorbate reductase. There was a higher activity of antioxidative enzymes at the beginning of the diapause period (November) compared to late diapause (February), while glutathione and ascorbate were higher in February. Similarly, there was a lower activity of the hexose monophosphate shunt enzymes in February. Exposure of larvae to -12°C resulted in an elevation of hexose monophosphate shunt enzyme activity, especially in November. This was accompanied by a significant increase in glycerol content in February. Changes in ascorbate levels and dehydroascorbate reductase activity in both experimental groups (-12°C and 8°C) suggest a connection between the antioxidative system, metabolism during diapause and cold hardiness. Our results support the notion that antioxidative defense in larvae of Ostrinia nubilalis is closely connected with metabolic changes characteristic of diapause, mechanisms of cold hardiness involved in diapause and the maintenance of a stable redox state.

Variations in antioxidant defense during the development of the solitary bee Osmia bicornis

“…In larvae, antioxidant levels are crucial Antioxidant system of Osmia bees for subsequent developmental stages (JovanovicGalovic et al 2004). It has been suggested that antioxidant enzymes have overlapping functions to promote stable development and homeostasis during diapause and metamorphosis (Stanic et al 2004). The above observations explain the activity of antioxidant enzymes and non-enzymatic antioxidants in all examined stages of O. bicornis ontogenesis (Figs.…”

The antioxidant system in diapausing and active red mason bee Osmia bicornis

“…No statistically significant changes in total antioxidant status, GSH, superoxide dismutase or nonspecific peroxidase values are noted in overwintering males or females. The absence of changes in superoxide dismutase level is unexpected because this enzyme protects other insects against oxidative stress induced by low temperatures (Grubor‐Lajsic et al ., ; Stanic et al ., ; Sim & Denlinger, ). Other studies demonstrate that superoxide dismutase, catalase and peroxidase have protective functions in diapausing Culex pipens and Grapholita molesta (Sim & Denlinger, ; He et al ., ).…”

“…The differences between the different species could be attributed to variations in diapause behaviour of the analyzed insects (Koštál, ). The discrepant results reported by various studies could also indicate the specificity of antioxidant systems in different insects (Joanisse & Storey, ; Stanic et al ., ; He et al ., ). In diapausing C. pipiens , catalase protects the resting ovaries against oxidative damage (Sim & Denlinger, ).…”

Potential role of hydrogen peroxide and melanin in the cold hardiness of Ostrinia nubilalis (Lepidoptera: Pyralidae)

“…Our previous studies (Stanic et al, 2004) show that the biosynthesis of glycerol as a cryoprotectant is closely associated with antioxidant enzymes in larvae of the European corn borer, Ostrinia nubilalis. The elevated activity of enzymes in the pentose phosphate pathway in Ostrinia larvae exposed to cold accord with data on the glycerol synthesis pathway (Nordin et al, 1984).…”