Inhibition of mitochondrial respiration under hypoxia and increased antioxidant activity after reoxygenation of <i>Tribolium castaneum</i>

<div><p>Regulating the air in low-oxygen environments protects hermetically stored grains from storage pests damage. However, pests that can tolerate hypoxic stress pose a huge challenge in terms of grain storage. We used various biological approaches to determine the fundamental mechanisms of <i>Tribolium castaneum</i> to cope with hypoxia. Our results indicated that limiting the available oxygen to <i>T</i>. <i>castaneum</i> increased glycolysis and inhibited the Krebs cycle, and that accumulated pyruvic acid was preferentially converted to lactic acid via anaerobic metabolism. Mitochondrial aerobic respiration was markedly suppressed for beetles under hypoxia, which also might have led to mitochondrial autophagy. The enzymatic activity of citrate synthase decreased in insects under hypoxia but recovered within 12 h, which suggested that the beetles recovered from the hypoxia. Moreover, hypoxia-reperfusion resulted in severe oxidative damage to insects, and antioxidant levels increased to defend against the high level of reactive oxygen species. In conclusion, our findings show that mitochondria were the main target in <i>T</i>. <i>castaneum</i> in response to low oxygen. The beetles under hypoxia inhibited mitochondrial respiration and increased antioxidant activity after reoxygenation. Our research advances the field of pest control and makes it possible to develop more efficient strategies for hermetic storage.</p></div

The activity of (A) SOD, (B) CAT, (C) GST and (D) MDA concentration of <i>T</i>. <i>castaneum</i> under normoxia and hypoxia-reperfusion.

<p>The bars represent means ± SE of three replicates. One-way ANOVA followed by Tukey’s range test was used for pairwise comparison of the difference between groups for mean separation (<i>P</i> < 0.05).</p

GO enrichment analysis of genes involves in the hypoxia resistance.

<p>The GO terms are sorted by —Log 10 of the enrichment <i>P</i>-value, which represent the enrichment significance of GO terms. The enrichment of GO terms are shown by comparing DEG with the whole genome.</p

Variation in citrate synthase activity of <i>T</i>. <i>castaneum</i> under normoxia and hypoxia-reperfusion.

<p>The citrate synthase activity of different groups was analyzed by one-way ANOVA. Results are shown as mean ± SE. Tukey’s multiple test was used for pairwise comparison of the difference between treatment for mean separation (<i>P</i> < 0.05).</p

Some hypoxia-response DEGs in the RNA-seq.

<p>Some hypoxia-response DEGs in the RNA-seq.</p

qRT-PCR analysis of selected transcripts to confirm expression profiles identified by RNA-seq.

<p><i>Tc</i>ELOVL, elongation of very long chain fatty acids protein 7; <i>Tc</i>MRP, ATP-binding cassette subfamily C (CFTR/MRP) member 4; <i>Tc</i>HSP70, heat shock 70kDa protein; <i>Tc</i>MAPK, MAP kinase; <i>Tc</i>DUSP, Dual specificity MAP kinase phosphatase; <i>Tc</i>SD, superoxide dismutase, Cu-Zn family; <i>Tc</i>AG, alpha-glucosidase; <i>Tc</i>DACHS, DACHS, Hippo signling pathway; <i>Tc</i>FJBP Four-jointed box protein 1 (FJBP). Value represents mean ± SE of three independent PCR amplifications and quantifications.</p