A Molecular View of Autophagy in Lepidoptera

Abstract

Metamorphosis represents a critical phase in the development of holometabolous insects, during which the larval body is completely reorganized: in fact, most of the larval organs undergo remodeling or completely degenerate before the final structure of the adult insect is rebuilt. In the past, increasing evidence emerged concerning the intervention of autophagy and apoptosis in the cell death processes that occur in larval organs of Lepidoptera during metamorphosis, but a molecular characterization of these pathways was undertaken only in recent years. In addition to developmentally programmed autophagy, there is growing interest in starvation-induced autophagy. Therefore we are now entering a new era of research on autophagy that foreshadows clarification of the role and regulatory mechanisms underlying this self-digesting process in Lepidoptera. Given that some of the most important lepidopteran species of high economic importance, such as the silkworm, Bombyx mori, belong to this insect order, we expect that this information on autophagy will be fully exploited not only in basic research but also for practical applications.

The role of autophagy in the midgut epithelium of Parachela (Tardigrada)

“…However, three types are best known: apoptosis, necrosis and autophagy. They are common processes that occur in the digestive epithelia of invertebrates (Malagoli et al 2010; Franzetti et al 2012; Romanelli et al 2014, 2016; Wilczek et al 2014; Lipovšek and Novak 2015; Rost-Roszkowska et al 2015, 2016; Sonakowska et al 2016). When the cytoplasm is rich in autophagic structures, apoptosis and/or necrosis is activated (Levine and Yuan 2005; Giusti et al 2007; Tettamanti et al 2007; Rost-Roszkowska et al 2013b).…”

“…Mitophagy is a type of selected autophagy in which mainly damaged or non-active mitochondria are neutralized and discharged from the cytoplasm (Włodarczyk et al 2017). Selective autophagy, in contrast to a non-selective process, forces the specific structures or organelles into the autophagosomes to cause them to be eventually digested (Mijaljica et al 2012; Shaid et al 2013; Romanelli et al 2014, 2016). Depending on the organelles that are enclosed inside autophagosomes, we can distinguish mitophagy, reticulophagy, lipophagy, nucleophagy, etc.…”

“…The reserve material is commonly accumulated in the cytoplasm of the digestive cells in insects (Lipovšek et al 2011; Amiri and Bandani 2013; Lipovšek and Novak 2015), myriapods (Chajec et al 2012, 2014; Sosinka et al 2014), crustaceans (Sousa and Petriella 2000; Sonakowska et al 2016) and tardigrades (Rost-Roszkowska et al 2011; Hyra et al 2016). It can be exploited due to digestion that involves autophagy during the natural periods of starvation such as the hibernation (Lipovšek et al 2011; Kamińska et al 2016), molting (Franzetti et al 2012; Romanelli et al 2014, 2016) or during starvation that is caused by a lack of food in the environment in which the animal lives (Zaffagnini and Martens 2016). Therefore, it is starvation-induced autophagy, in contrast to a starvation-independent process (Zaffagnini and Martens 2016).…”

Sequential steps of macroautophagy and chaperone-mediated autophagy are involved in the irreversible process of posterior silk gland histolysis during metamorphosis ofBombyx mori

“…It has been shown that macroautophagy plays a central role in remodeling organs in Diptera (mosquito and fruit fly; Coppens, 2011;Tracy and Baehrecke, 2013), Lepidoptera (silkworm; Goncu and Parlak, 2008;Franzetti et al, 2012;Romanelli et al, 2014) and Hymenoptera (honey bee; Silva-Zacarin et al, 2008;Santos et al, 2015). However, it is not clear whether CMA is also involved in the remodeling process.…”

Roles and regulation of autophagy and apoptosis in the remodelling of the lepidopteran midgut epithelium during metamorphosis

“…This evidence has prompted the hypothesis of a causative role of autophagy in the demise of these tissues, although the existence of autophagic cell death in these insects has never been clearly and definitively demonstrated2128.…”