Steroid Hormone 20-hydroxyecdysone Promotes Autophagy Associated Gene 12 Expression For Insect Midgut Programmed Cell Death

Background、Scientific problem and SignificanceDuring the development of insect, the morphological will change many times, most species are through egg, larva, even through a pupa stage to become a adult. Insect development undergo molting and metamorphosis, molting was the necessary for insect growth. During metamorphosis, the internal structure of the insect will change, showing that the larval midgut undergo PCD and the adult midgut formed.20-Hydroxyecdysone (20E) can promote metamorphosis and PCD during insect development. PCD includes apoptosis and autophagy, mainly. Autophagy allows the orderly degradation and recycling of cellular components. During this process, targeted cytoplasmic constituents are isolated from the rest of the cell within a double-membraned vesicle known as an autophagosome. The autophagosome then fuses with a lysosome and the contents are degraded and recycled. Apoptosis is refers to the cells in a certain physiological or pathological conditions, under the control of the internal genetic mechanism automatically end the process of life. Apoptosis is a active process not a passive process, it involves a series of genes activation, expression and regulation; it’s not a pathological condition, a phenomenon of self-injury, but for better adapt to living environment and actively strive for a death process. During the midgut reconstruction, both autophagy and apoptosis happened. Autophagy formation depends on a series of ATG protein interaction. Two kinds of ubiquitin-like protein system play important role in the process of the formation of autophagy membrane, one is ATG12-ATG5-ATG16L1, used as E3 enzymes make LC3 lipidation and extension of auxiliary autophagy membrane; the other one is ATG8/LC3, under the function of ATG7-. ATG3 and ATG12-ATG5, combined with phosphatidyl ethanolamine and fixed on the autophagy membrane. During the process of insect development, PCD is indispensable to remove unnecessary cells, remove the number of cells limit and maintain a steady state in the body. This article mainly research on the role of ATG12 in intestinal tissue reconstruction, as well as the relationship between autophagy and apoptosis, and on the Helicoverpa armigera epidermal cell lines for further verification, to provide target genes for pests control.Results and conclusionWe use Helicoverpa armigera midgut and epidermal cell line as experimental object, mainly take a technique called RNA interference to study the function of autophagy related protein ATG12 in Helicoverpa armigera metamorphosis development. Get the following results:the ATG12-ATG5 was expressed in epidermis, midgut and fat body; expression quantity will rise significantly in metamorphosis and upregulated by 20E; After ATG12 interference, the pupation time was delay and form abnormal pupa. indicating ATG12 plays an important role in the process of midgut PCD; The results of immunohistochemical showing after interference ATG12, the midgut PCD was influenced; The results of interference on Helicoverpa armigera epidermal cell lines show that affect the formation of autophagosome and the occurrence of apoptosis.Innovative points and significance of researchDiscover that the combination of ATG12 and ATG5 is upregulated by 20E, ATG12 plays an important role in the process of midgut reconstruction; In the process of midgut PCD, if autophagy be inhibited, apoptosis may also be affected. These results have a certain reference to the study the Helicoverpa armigera midgut reconstruction process.