Functional importance of groups I and II chitinases, CHT5 and CHT10, in turnover of chitinous cuticle during embryo hatching and post-embryonic molting in the red flour beetle, Tribolium castaneum.

Chitinases (CHT) comprise a large gene family in insects and have been classified into at least eleven subgroups. Many studies involving RNA interference (RNAi) have demonstrated that depletion of group I (CHT5s) and group II (CHT10s) CHT transcripts causes lethal molting arrest in several insect species including the red flour beetle, Tribolium castaneum, presumably due to failure of degradation of chitin in their old cuticle. In this study we investigated the functions of CHT5 and CHT10 in turnover of chitinous cuticle in T.

Nuclear receptor estrogen-related receptor modulates antimicrobial peptide expression for host innate immunity in Tribolium castaneum.

Antimicrobial peptides (AMPs) are core components of innate immunity to protect insects against microbial infections. Nuclear receptors (NRs) are ligand-dependent transcription factors that can regulate the expression of genes critical for insect development including molting and metamorphosis. However, the role of NRs in host innate immune response to microbial infection remains poorly understood in Tribolium castaneum (T.

Nuclear receptor HR3 mediates transcriptional regulation of chitin metabolic genes during molting in Tribolium castaneum.

Background: Chitin, a major component of insect cuticles, plays a critical role in insect molting and morphogenesis. Thus, coordination of chitin remodeling during insect development requires tight transcriptional control of the chitin metabolism genes involved in chitin synthesis, assembly and degradation. However, the molecular mechanism underlying transcriptional coordination of chitin metabolism genes during beetle development is not yet completely understood.

Chitin deacetylases are necessary for insect femur muscle attachment and mobility.

Muscle attachment sites (MASs, apodemes) in insects and other arthropods involve specialized epithelial cells, called tendon cells or tenocytes, that adhere to apical extracellular matrices containing chitin. Here, we have uncovered a function for chitin deacetylases (CDAs) in arthropod locomotion and muscle attachment using a double-stranded RNA-mediated gene-silencing approach targeted toward specific CDA isoforms in the red flour beetle, (). Depletion of TcCDA1 or the alternatively spliced TcCDA2 isoform, TcCDA2a, resulted in internal tendon cuticle breakage at the femur-tibia joint, muscle detachment from both internal and external tendon cells, and defective locomotion.

AA15 lytic polysaccharide monooxygenase is required for efficient chitinous cuticle turnover during insect molting.

Microbial lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of crystalline polysaccharides including chitin and cellulose. The discovery of a large assortment of LPMO-like proteins widely distributed in insect genomes suggests that they could be involved in assisting chitin degradation in the exoskeleton, tracheae and peritrophic matrix during development. However, the physiological functions of insect LPMO-like proteins are still undetermined.

Ultrastructural analysis of beetle larva cuticles during infection with the entomopathogenic fungus, Beauveria bassiana.

Background: Beauveria bassiana is one of the commercially available entomopathogenic fungi (EPF), and a number of isolates with high virulence and broad host spectrum have been used to control agricultural and forest pests. Although the functional importance of genes in EPFs' pathogenesis have been extensively studied, the precise ultrastructural mechanism of the fungal infection, particularly penetration of the host insect cuticles, is not well understood.

Results: In this study, we investigated the morphology and ultrastructure of the larval cuticle of the red flour beetle, Tribolium castaneum, after treatment with B.

Superoxide dismutase 6 is required during metamorphosis for the development of properly movable legs in Tribolium castaneum.

The body form of holometabolous insects dramatically transforms from larval to adult stages during metamorphosis that occurs in the pupal stage. The larval disorganization and then new adult tissues are built up at this time. In motoneuron, larval neuronal cells degenerate, and new adult neurons are remodeled.

Yellow-y Functions in Egg Melanization and Chorion Morphology of the Asian Tiger Mosquito, .

The Asian tiger mosquito, , is one of the most serious public health pests, which can transmit various vector-borne diseases. Eggs from this mosquito species become dark black shortly after oviposition and exhibit high desiccation resistance. Some of the Yellow proteins that act as dopachrome conversion enzymes (DCEs) are involved in the tyrosine-mediated tanning (pigmentation and sclerotization) metabolic pathway that significantly accelerates melanization reactions in insects.

Insect Cuticular Chitin Contributes to Form and Function.

Chitin contributes to the rigidity of the insect cuticle and serves as an attachment matrix for other cuticular proteins. Deficiency of chitin results in abnormal embryos, cuticular structural defects and growth arrest. When chitin is not turned over during molting, the developing insect is trapped inside the old cuticle.

Gene functions in adult cuticle pigmentation of the yellow mealworm, Tenebrio molitor.

In many arthropod species including insects, the cuticle tanning pathway for both pigmentation and sclerotization begins with tyrosine and is responsible for production of both melanin- and quinoid-type pigments, some of which are major pigments for body coloration. In this study we identified and cloned cDNAs of the yellow mealworm, Tenebrio molitor, encoding seven key enzymes involved in this pathway including tyrosine hydroxylase (TmTH), DOPA decarboxylase (TmDDC), laccase 2 (TmLac2), Yellow-y (TmY-y), arylalkylamine N-acetyltransferase (TmAANAT1), aspartate 1-decarboxylase (TmADC) and N-β-alanyldopamine synthase (Tmebony). Expression profiles of these genes during development were analyzed by real-time PCR, revealing development-specific patterns of expression.

Cuticular protein with a low complexity sequence becomes cross-linked during insect cuticle sclerotization and is required for the adult molt.

In the insect cuticle, structural proteins (CPs) and the polysaccharide chitin are the major components. It has been hypothesized that CPs are cross-linked to other CPs and possibly to chitin by quinones or quinone methides produced by the laccase2-mediated oxidation of N-acylcatechols. In this study we investigated functions of TcCP30, the third most abundant CP in protein extracts of elytra (wing covers) from Tribolium castaneum adults.

A Major Facilitator Superfamily protein encoded by TcMucK gene is not required for cuticle pigmentation, growth and development in Tribolium castaneum.

Insect cuticle pigmentation and sclerotization (tanning) are vital physiological processes for insect growth, development and survival. We have previously identified several colorless precursor molecules as well as enzymes involved in their biosynthesis and processing to yield the mature intensely colored body cuticle pigments. A recent study indicated that the Bombyx mori (silkmoth) gene, BmMucK, which encodes a protein orthologous to a Culex pipiens quiquefasciatus (Southern house mosquito) cis,cis, muconate transporter, is a member of the "Major Facilitator Superfamily" (MFS) of transporter proteins and is associated with the appearance of pigmented body segments of naturally occurring body color mutants of B.

Cloning, characterization and effect of TmPGRP-LE gene silencing on survival of Tenebrio molitor against Listeria monocytogenes infection.

Peptidoglycan recognition proteins (PGRPs) are a family of innate immune molecules that recognize bacterial peptidoglycan. PGRP-LE, a member of the PGRP family, selectively binds to diaminopimelic acid (DAP)-type peptidoglycan to activate both the immune deficiency (Imd) and proPhenoloxidase (proPO) pathways in insects. A PGRP-LE-dependent induction of autophagy to control Listeria monocytogenes has also been reported.