Abstract
Oxidative stress promotes pupation in some holometabolous insects. The levels of superoxide, a reactive oxygen species (ROS), are increased and superoxide dismutase 1 (BmSod1) and superoxide dismutase 2 (BmSod2) are decreased during metamorphic events in silkworm (Bombyx mori). These observations strongly suggest that pupation is initiated by oxidative stress via the down-regulation of BmSod1 and BmSod2. However, the molecular mechanisms underlying ROS production during metamorphic events in silkworm remain unknown. To investigate these molecular mechanisms, the peripheral proteins of BmSod1 and BmSod2 were identified and characterized using dry and wet approaches in this study. Based on the results, silkworm heat shock protein 60 (BmHsp60) was identified as an interacting partner of BmSod2, which belongs to the Fe/MnSOD family. Furthermore, the present study results showed that BmHsp60 mRNA expression levels were increased in response to oxidative stress caused by ultraviolet radiation and that BmHsp60 protein levels (but not mRNA levels) were decreased during metamorphic events, which are regulated by the molting hormone 20-hydroxyecdysone. These findings improve our understanding of the mechanisms by which holometabolous insects control ROS during metamorphosis.
Highlights
Reactive oxygen species (ROS) are constantly generated in all aerobic biological systems as the natural products of oxidative metabolism and are produced by tissues and cells in response to environmental stress, extreme temperatures, and chemical agents
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
We have shown that BmSod1 and BmSod2 are localized in the cytosol and mitochondria, respectively [12]
Summary
Reactive oxygen species (ROS) are constantly generated in all aerobic biological systems as the natural products of oxidative metabolism and are produced by tissues and cells in response to environmental stress, extreme temperatures, and chemical agents. ROS are toxic due to their high reactivity, causing oxidative damage to proteins, lipids, and nucleic acids. They are related to aging and lifespan [1]. Despite this toxicity, ROS are necessary for normal development in holometabolous insects. Several insect studies have revealed the relationship between ROS generation in response to environmental oxidative stress and developmental processes. The administration of isosorbide dinitrate, a NO donor, to the beetle Homoderus mellyi Parry rapidly promotes the process of pupation [3]. ROS generation in response to environmental oxidative stress seems to be closely associated with the initiation of metamorphic events in insects
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