Lack of signal peptide in insect prophenoloxidase to avoid glycosylation to damage the zymogen activity.

Insect prophenoloxidases (PPOs) are important immunity proteins for defending against the invading pathogens and parasites. As a Type-Ⅲ copper-containing proteins, unlike Homo sapiens tyrosinases, the insect PPOs and most bacterial tyrosinases contain no signal peptides for unknown reason, however they can still be released. To this end, we fused different signal peptides to Drosophila melanogaster PPOs for in vitro and in vivo expression, respectively.

Regulation of intestinal stem cell activity by a mitotic cell cycle regulator Polo in Drosophila.

Maintaining a definite and stable pool of dividing stem cells plays an important role in organ development. This process requires an appropriate progression of mitosis for proper spindle orientation and polarity to ensure the ability of stem cells to proliferate and differentiate correctly. Polo-like kinases (Plks)/Polo are the highly conserved serine/threonine kinases involved in the initiation of mitosis as well as in the progression of the cell cycle.

Lysozyme inhibits postharvest physiological deterioration of cassava.

After harvest, cassava (Manihot esculenta Crantz) storage roots undergo rapid postharvest physiological deterioration, producing blue-brown discoloration in the vasculature due to the production of polyphenolics (mainly quinones and coumarins) by enzymes such as polyphenol oxidase (PPO). Here, we report the application of hen egg-white lysozyme (HEWL), a natural PPO inhibitor, in transgenic cassava to repress the symptoms of postharvest physiological deterioration. The HEWL-expressing transgenic plants had lower levels of the two main cassava coumarins tested, scopoletin and scopolin, compared with wild type.

Prophenoloxidase-positive tubes derived from the hindguts may be the doorkeeper to detoxify the waste metabolites collected by Malpighian tubules in Lepidoptera insects.

Prophenoloxidase (PPO), an important immunity protein in insects, is mainly produced by hemocytes and released into the hemolymph upon cell lysis. In addition, PPO can also be produced by epidermal cells in the foregut to detoxify the toxic plant secondary metabolites and in the hindgut to kill pathogens through PPO-induced melanization. Previously, we noticed a pair of tubes extended from the larval hindgut became melanized upon staining in dopamine dissolved in 30% ethanol.

Drosophila H2Av negatively regulates the activity of the IMD pathway via facilitating Relish SUMOylation.

Insects depend on the innate immune response for defense against a wide array of pathogens. Central to Drosophila immunity are antimicrobial peptides (AMPs), released into circulation when pathogens trigger either of the two widely studied signal pathways, Toll or IMD. The Toll pathway responds to infection by Gram-positive bacteria and fungi while the IMD pathway is activated by Gram-negative bacteria.

Gut microbiome modulates Drosophila aggression through octopamine signaling.

Gut microbiome profoundly affects many aspects of host physiology and behaviors. Here we report that gut microbiome modulates aggressive behaviors in Drosophila. We found that germ-free males showed substantial decrease in inter-male aggression, which could be rescued by microbial re-colonization.

Loss of control of the culturable bacteria in the hindgut of Bombyx mori after Cry1Ab ingestion.

Bt protein, produced by Bacillus thuringiensis, can bind receptors to destroy the physiological functions of the insect midgut. It is unknown whether Bt can also target the hindgut and influence its defense against fecal bacteria. Here we show that Crystal protein 1Ab (Cry1Ab), a Bt protein, was detected in the larval hindgut contents of Bombyx mori after ingestion of this toxin protein.

Peptide Hormones in the Insect Midgut.

Insects produce many peptide hormones that play important roles in regulating growth, development, immunity, homeostasis, stress, and other processes to maintain normal life. As part of the digestive system, the insect midgut is also affected by hormones secreted from the prothoracic gland, corpus allatum, and various neuronal cells; these hormones regulate the secretion and activity of insects' digestive enzymes and change their feeding behaviors. In addition, the insect midgut produces certain hormones when it recognizes various components or pathogenic bacteria in ingested foods; concurrently, the hormones regulate other tissues and organs.

A M35 family metalloprotease is required for fungal virulence against insects by inactivating host prophenoloxidases and beyond.

A diverse family of metalloproteases (MPs) is distributed in eukaryotes. However, the functions of MPs are still understudied. We report that seven MPs belonging to the M35 family are encoded in the genome of the insect pathogenic fungus .

Beauveria bassiana ribotoxin inhibits insect immunity responses to facilitate infection via host translational blockage.

Entomopathogenic fungi are promising bio-pesticides. To facilitate infection, fungi recruit multiple virulence factors and deploy different molecular strategies to evade host immunity. Fungal ribotoxins are extracellular secreted ribonucleases (RNases) with ribotoxic cytotoxicity and insecticidal activity.

Aluminum toxicity related to SOD and expression of presenilin and CREB in Bombyx mori.

Aluminum (Al) is an important environmental metal factor that can be potentially associated with pathological changes leading to neurotoxicity. The silkworm, Bombyx mori, is an important economic insect and has also been used as a model organism in various research areas. However, the toxicity of Al on silkworm physiology has not been reported.

Effect of the insect phenoloxidase on the metabolism of l-DOPA.

Insect prophenoloxidase (PPO) induces melanization around pathogens. Before melanization, PPO is cleaved into phenoloxidase (PO) by serine proteases. Insect PPO can also be activated by exogenous proteases secreted by pathogens as well as by other compounds, such as ethanol and cetylpyridinium chloride (CPC).

Analysis of the functions of the signal peptidase complex in the midgut of Tribolium castaneum.

Signal peptidase complexes (SPCs) are conserved from bacteria to human beings, and are typically composed of four to five subunits. There are four genes encoding SPC proteins in the red flour beetle, Tribolium castaneum. To understand their importance to insect development, double-stranded RNA for each SPC gene was injected into red flour beetles at the early larval and adult stages.

Prophenoloxidase-Mediated Immunity to Delay Fungal Infection after Insect Ecdysis.

Skin immunity protects animals from airborne pathogen infection. Unlike mammals, arthropods, including insects, undergo periodic ecdysis to grow and develop. Newly molted insects emerge with unsclerotized thin cuticles but successfully escape pathogenic infections during the post-molt period.

Differentiation of lepidoptera scale cells from epidermal stem cells followed by ecdysone-regulated DNA duplication and scale secreting.

Integuments are the first line to protect insects from physical damage and pathogenic infection. In lepidopteran insects, they undergo distinct morphology changes such as scale formation during metamorphosis. However, we know little about integument development and scale formation during this stage.

Analysis of gene expression in the midgut of Bombyx mori during the larval molting stage.

Background: Insects can be models for understanding human intestinal infection and pathology. Molting, a special period during which the old insect cuticle is shed and a new one is produced, is crucial for insect development. Holometabolous insects may experience several larva-to-larva moltings to become larger, a pupal molt and adult eclosion to become adults.

Gut immunity in Lepidopteran insects.

Lepidopteran insects constitute one of the largest fractions of animals on earth, but are considered pests in their relationship with man. Key to the success of this order of insects is its ability to digest food and absorb nutrition, which takes place in the midgut. Because environmental microorganisms can easily enter Lepidopteran guts during feeding, the innate immune response guards against pathogenic bacteria, virus and microsporidia that can be devoured with food.

DNA duplication is essential for the repair of gastrointestinal perforation in the insect midgut.

Invertebrate animals have the capacity of repairing wounds in the skin and gut via different mechanisms. Gastrointestinal perforation, a hole in the human gastrointestinal system, is a serious condition, and surgery is necessary to repair the perforation to prevent an abdominal abscess or sepsis. Here we report the repair of gastrointestinal perforation made by a needle-puncture wound in the silkworm larval midgut.

Plant phenolics are detoxified by prophenoloxidase in the insect gut.

Plant phenolics are a group of important secondary metabolites that are toxic to many animals and insects if ingested at high concentrations. Because most insects consume plant phenolics daily, they have likely evolved the capacity to detoxify these compounds. Here, we used Drosophila melanogaster, Bombyx mori and Helicoverpa armigera as models to study the metabolism of plant phenolics by prophenoloxidases.

Gr33a modulates Drosophila male courtship preference.

In any gamogenetic species, attraction between individuals of the opposite sex promotes reproductive success that guarantees their thriving. Consequently, mate determination between two sexes is effortless for an animal. However, choosing a spouse from numerous attractive partners of the opposite sex needs deliberation.

Functional analysis of insect molting fluid proteins on the protection and regulation of ecdysis.

Molting fluid accumulates between the old and new cuticles during periodical ecdysis in Ecdysozoa. Natural defects in insect ecdysis are frequently associated with melanization (an immunity response) occurring primarily in molting fluids, suggesting that molting fluid may impact immunity as well as affect ecdysis. To address this hypothesis, proteomic analysis of molting fluids from Bombyx mori during three different types of ecdysis was performed.

Insect prophenoloxidase: the view beyond immunity.

Insect prophenoloxidase (PPO) is an important innate immunity protein due to its involvement in cellular and humoral defense. It belongs to a group of type-3 copper-containing proteins that occurs in almost all organisms. Insect PPO has been studied for over a century, and the PPO activation cascade is becoming clearer.

Thermolysin damages animal life through degradation of plasma proteins enhanced by rapid cleavage of serpins and activation of proteases.

Thermolysin, a metallopeptidase secreted by pathogenic microbes, is concluded as an important virulence factor due to cleaving purified host proteins in vitro. Using the silkworm Bombyx mori as a model system, we found that thermolysin injection into larvae induces the destruction of the coagulation response and the activation of hemolymph melanization, which results in larval death. Thermolysin triggers the rapid degradation of insect and mammalian plasma proteins at a level that is considerably greater than expected in vitro and/or in vivo.