Superoxide dismutase down-regulation and the oxidative stress is required to initiate pupation in Bombyx mori

Abstract

Perhaps, oxidative stress progresses pupation in some Lepidopteran insects; however, the reasons for this remain obscure. In our previous study, we clarified Bombyx mori SOD1 (BmSOD1) and B. mori SOD2 (BmSOD2) proteins respond in common to ultraviolet irradiation (UV) oxidative stress and metamorphosis. This result strongly suggested pupation initiates by oxidative stress and might mediate by down-regulation of expression of BmSOD1 and BmSOD2 proteins. Thus, we examined about these relationships in B. mori in this study. In the microarray data reanalysis, we found the Notch signaling pathways as the common pathways in pupation and UV oxidative stress in B. mori. Also, we showed a molting hormone, 20-hydroxyecdysone, leads not only generation of superoxide but also downregulation of the expression of BmSOD proteins during pupation in B. mori. Our findings can contribute to a deeper understanding of how biological defense systems work against environmental oxidative stress.

Characterization of Heat Shock Protein 60 as an Interacting Partner of Superoxide Dismutase 2 in the Silkworm, Bombyx mori, and Its Response to the Molting Hormone, 20-Hydroxyecdysone

“…The expression levels of BmHsp60 were normalized against that of BmActin as an endogenous control. Antibody specificity has been confirmed in previous studies [ 12 , 23 ].…”

“…The antibodies or antiserum used for immunoblotting after the co-immunoprecipitation assay are shown in Supplementary Table S1 . Antibody and antiserum specificity has been confirmed in previous studies [ 12 , 23 ].…”

“…To predict genes that are co-expressed with BmSod1 or BmSod2 , a public RNA-Seq dataset obtained from five tissues derived from silkworm larvae was re-analyzed by WGCNA. Previously, we have shown that BmSod1 and BmSod2 are localized in the cytosol and mitochondria, respectively [ 12 ]. Thus, prior to WGCNA, 5077 genes encoding proteins localized in the cytosol and 1895 genes encoding proteins localized in the mitochondria were extracted from the gene model in SilkBase using Deeploc.…”

“…Increased superoxide levels and decreased BmSod expression in the fat body cells of silkworms at pre-pupal stages are required to initiate pupation [ 12 ]. To investigate whether the expression of BmHsp60 is involved in molting and pupation, BmHsp60 protein expression in the fat bodies of fourth instar larvae, fifth instar larvae, pupae, and adults were examined.…”

“…BmSod1 and BmSod2 mRNA are abundantly expressed in fat bodies, unlike the other five BmSod genes [ 11 ]. Furthermore, we have shown that BmSod1 and BmSod2 protein expressions in the fat body are downregulated during pupation [ 12 ].…”