Effect of Cold Acclimation on Selected Metabolic Enzymes During Diapause in The European Corn Borer Ostrinia nubilalis (Hbn.)

Abstract

The European corn borer, Ostrinia nubilalis Hbn., is a pest Lepidopteran species whose larvae overwinter by entering diapause, gradually becoming cold-hardy. To investigate metabolic changes during cold hardening, activities of four metabolic enzymes-citrate synthase (CS), lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured in whole-body homogenates of pupae, non-diapausing and diapausing larvae acclimated to 5 °C, −3 °C and −16 °C. The highest CS activity was detected in non-diapausing larvae, reflecting active development, while the highest in vitro LDH activity was recorded in diapausing larvae at temperatures close to 0 °C, evidencing a metabolic switch towards anaerobic metabolism. However, in-gel LDH activity showed that production of pyruvate from lactate is triggered by sub-zero temperatures. The activities of both aminotransferases were highest in non-diapausing larvae. Our findings suggest that during diapause and cold hardening the aminotransferases catalyse production of L-alanine, an important cryoprotectant, and L-aspartate, which is closely tied to both transamination reactions and Krebs cycle. The results of this study indicate that, during diapause, the activity of metabolic enzymes is synchronized with exogenous factors, such as temperatures close to 0 °C. These findings support the notion that diapause is metabolically plastic and vibrant, rather than simply a passive, resting state.

Acclimations to Cold and Warm Conditions Differently Affect the Energy Metabolism of Diapausing Larvae of the European Corn Borer Ostrinia nubilalis (Hbn.)

“…In larval diapause of O. nubilalis exposure to low temperatures increases the production of ROS, such as hydrogen peroxide ( Kojić et al, 2009 ). Thus, the antioxidative defense system (ADS) in this species is connected with other biochemical adaptations to winter season conditions, such as the biosynthesis of polyol cryoprotectants ( Grubor-Lajšić et al, 1997 ; Jovanović-Galović et al, 2004 , 2007 ; Stanić et al, 2004 ; Popović et al, 2015 ; Uzelac et al, 2020 ). In addition, the ADS is supported by intensive pentose phosphate pathway (PPP) activity during the first months of diapause in O. nubilalis , since this pathway is a unique source of NADPH in the cell ( Stanić et al, 2004 ).…”

“…During diapause, NADPH serves as a source of reducing equivalents in antioxidant protection, representing a substrate for the regeneration of antioxidant molecules such as GSH, thioredoxin, glutaredoxin, and others. Also, NADPH is necessary for biosynthetic processes, such as the production of glycerol which participates in the protection of cells from low temperatures ( Stanić et al, 2004 ; Blagojević, 2007 ; Kojić et al, 2010 , 2018 ; Purać et al, 2015 ; Uzelac et al, 2020 ). In addition to the concentration increase of the NADP + in dca2 and dca4 larvae, a significant increase in the transcription of the thioredoxin ( trx ) gene was found in the same groups ( Popović et al, 2015 ).…”

“…This leads to the lowering of the insect’s supercooling point to below −20°C and the development of cold hardiness ( Nordin et al, 1984 ; Grubor-Lajšić et al, 1991 ; Andreadis et al, 2008 ). Despite the fact that diapause and cold hardiness in O. nubilalis have been extensively studied at physiological and biochemical levels ( Beck et al, 1969 ; Beck and Shane, 1969 ; Beck, 1989 ; Grubor-Lajšić et al, 1991 ; Stanić et al, 2004 ; Jovanović-Galović et al, 2007 ; Kojić et al, 2009 , 2018 ; Blagojević et al, 2011 ; Vukašinović et al, 2013 , 2015 , 2018 ; Purać et al, 2015 ; Uzelac et al, 2020 ), the exact molecular processes driving diapause development and increased stress-tolerance in this species remain insufficiently understood.…”

Cryoprotective Response as Part of the Adaptive Strategy of the Red Palm Weevil, Rhynchophorus ferrugineus, against Low Temperatures

“…We also found modest but significant increases in the hemolymph of cold-treated animals of other non-essential amino acids, such a serine and aspartic acid + asparagine, as well as of five essential amino acids (histidine, leucine, isoleucine, threonine and valine). An increase in serine [54], aspartic acid [55] and essential amino acids [43] in overwintering larvae or cold-treated insects has been previously reported in the literature. However, as in the case of alanine, it is not clear whether the accumulation of these amino acids is part of a cryoprotective response or the result of different metabolic pathways triggered by cold.…”

Computer tomography‐assisted visualization of the movement triggered by frost in Ostrinia nubilalis overwintering in maize stalks

“…During this essential process, the larva accumulates long‐chain carbohydrates (trehalose, ribulose, etc.) and glycerol in its body (Nordin et al ., 1984; Beck, 1989; Uzelac et al ., 2020).…”