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Melanin insect cuticle

Andreas Wuensch, Franziska Trusch, Nurul A Iberahim, Pieter van West
Oomycetes are eukaryotic pathogens infecting animals and plants. Amongst them Saprolegnia parasitica is a fish pathogenic oomycete causing devastating losses in the aquaculture industry. To secure fish supply, new drugs are in high demand and since fish experiments are time consuming, expensive and involve animal welfare issues the search for adequate model systems is essential. Galleria mellonella serves as a heterologous host model for bacterial and fungal infections. This study extends the use of G. mellonella for studying infections with oomycetes...
February 2018: Fungal Biology
Luana C Farnesi, Helena C M Vargas, Denise Valle, Gustavo L Rezende
Mosquito vectors lay their white eggs in the aquatic milieu. During early embryogenesis water passes freely through the transparent eggshell, which at this moment is composed of exochorion and endochorion. Within two hours the endochorion darkens via melanization but even so eggs shrink and perish if removed from moisture. However, during mid-embryogenesis, cells of the extraembryonic serosa secrete the serosal cuticle, localized right below the endochorion, becoming the third and innermost eggshell layer. Serosal cuticle formation greatly reduces water flow and allows egg survival outside the water...
October 2017: PLoS Neglected Tropical Diseases
Rhainer Guillermo-Ferreira, Esther Appel, Paulina Urban, Pitágoras C Bispo, Stanislav N Gorb
Some consider that the first winged insects had living tissue inside the wing membrane, resembling larval gills or developing wing pads. However, throughout the developmental process of the wing membrane of modern insects, cells and tracheoles in the lumen between dorsal and ventral cuticle disappear and both cuticles become fused. This process results in the rather thin rigid stable structure of the membrane. The herewith described remarkable case of the dragonfly Zenithoptera lanei shows that in some highly specialized wings, the membrane can still be supplemented by tracheae...
May 2017: Biology Letters
Miranda M A Whitten, Christopher J Coates
Melanins (eumelanin and pheomelanin) are synthesized in insects for several purposes including cuticle sclerotization and color patterning, clot formation, organogenesis, and innate immunity. Traditional views of insect immunity detail the storage of pro-phenoloxidases inside specialized blood cells (hemocytes) and their release upon recognition of foreign bodies. Activated phenoloxidases convert monophenols into reactive quinones in a two-step enzymatic reaction, and until recently, the mechanism of tyrosine hydroxylation remained a mystery...
July 2017: Pigment Cell & Melanoma Research
Ming-Hui Du, Zheng-Wen Yan, You-Jin Hao, Zhen-Tian Yan, Feng-Ling Si, Bin Chen, Liang Qiao
BACKGROUND: Phenol oxidases (POs) catalyze the oxidation of dopa and dopamine to melanin, which is crucial for cuticle formation and innate immune maintenance in insects. Although, Laccase 2, a member of the PO family, has been reported to be a requirement for melanin-mediated cuticle tanning in the development stages of some insects, whether it participates in cuticle construction and other physiological processes during the metamorphosis of mosquito pupae is unclear. METHODS: The association between the phenotype and the expression profile of Anopheles sinensis Laccase 2 (AsLac2) was assessed from pupation to adult eclosion...
April 4, 2017: Parasites & Vectors
Taichi Hamanaka, Keiko Nishizawa, Yuji Sakasegawa, Ayumi Oguma, Kenta Teruya, Hiroshi Kurahashi, Hideyuki Hara, Suehiro Sakaguchi, Katsumi Doh-Ura
Prion diseases are progressive fatal neurodegenerative illnesses caused by the accumulation of transmissible abnormal prion protein (PrP). To find treatments for prion diseases, we searched for substances from natural resources that inhibit abnormal PrP formation in prion-infected cells. We found that high-molecular-weight components from insect cuticle extracts reduced abnormal PrP levels. The chemical nature of these components was consistent with that of melanin. In fact, synthetic melanin produced from tyrosine or 3-hydroxy-l-tyrosine inhibited abnormal PrP formation...
March 15, 2017: Journal of Virology
Mi Young Noh, Bonwoo Koo, Karl J Kramer, Subbaratnam Muthukrishnan, Yasuyuki Arakane
In the insect cuticle tanning pathway (sclerotization and pigmentation), the enzyme arylalkylamine N-acetyltransferase (AANAT) catalyzes the acetylation of dopamine to form N-acetyldopamine (NADA), which is one of the major precursors for quinone-mediated tanning. In this study we characterized and investigated the function of TcAANAT1 in cuticle pigmentation of the red flour beetle, Tribolium castaneum. We isolated a full length TcAANAT1 cDNA that encodes a protein of 256 amino acid residues with a predicted GCN5-related acetyltransferase domain containing an acetyl-CoA binding motif...
December 2016: Insect Biochemistry and Molecular Biology
Mi Young Noh, Subbaratnam Muthukrishnan, Karl J Kramer, Yasuyuki Arakane
Adult beetles (Coleoptera) are covered primarily by a hard exoskeleton or cuticle. For example, the beetle elytron is a cuticle-rich highly modified forewing structure that shields the underlying hindwing and dorsal body surface from a variety of harmful environmental factors by acting as an armor plate. The elytron comes in a variety of colors and shapes depending on the coleopteran species. As in many other insect species, the cuticular tanning pathway begins with tyrosine and is responsible for production of a variety of melanin-like and other types of pigments...
October 2016: Current Opinion in Insect Science
Liang Qiao, Minghui Du, Xin Liang, Youjin Hao, Xiu He, Fengling Si, Ting Mei, Bin Chen
Tyrosine hydroxylase (TH), the initial enzyme in the melanin pathway, catalyzes tyrosine conversion into Dopa. Although expression and regulation of TH have been shown to affect cuticle pigmentation in insects, no direct functional studies to date have focused on the specific physiological processes involving the enzyme during mosquito development. In the current study, silencing of AsTH during the time period of continuous high expression in Anopheles sinensis pupae led to significant impairment of cuticle tanning and thickness, imposing a severe obstacle to eclosion in adults...
2016: Scientific Reports
Keith J King, Brent J Sinclair
Montane insects are at a higher risk of desiccation than their lowland counterparts and are expected to have evolved reduced water loss. Hemideina spp. (tree weta; Orthoptera: Anostostomatidae) have both lowland (Hemideina femorata, Hemideina crassidens and Hemideina thoracica) and montane (Hemideina maori and Hemideina ricta) species. H. maori has both melanic and yellow morphs. We use these weta to test two hypotheses: that montane insects lose water more slowly than lowland species, and that cuticular water loss rates are lower in darker insects than lighter morphs, because of incorporation of melanin in the cuticle...
July 2015: Journal of Experimental Biology
Haichen Yin, Muhammad Shakeel, Jing Kuang, Jianhong Li
Melanism is a common polymorphism in many insect species that also influences immune function. According to the thermal melanin hypothesis, ectothermic individuals from cooler environments have darker cuticles and higher polyphenol oxidase (PO) levels, which represent a better immunocompetence. In this study, the links among environmental temperature, melanism, and PO activity of Saccharosydne procerus (Matsumura) were examined. Most S. procerus have a black spot on their forewings at high temperatures in the field and in the laboratory...
2015: PloS One
Mi Young Noh, Karl J Kramer, Subbaratnam Muthukrishnan, Richard W Beeman, Michael R Kanost, Yasuyuki Arakane
Yellow protein (dopachrome conversion enzyme, DCE) is involved in the melanin biosynthetic pathway that significantly accelerates pigmentation reactions in insects. Recent studies have suggested that the insect yellow genes represent a rapidly evolving gene family generating functionally diverse paralogs, but the exact physiological functions of several yellow genes are still not understood. To study the function(s) of one of the yellow genes, yellow-e (TcY-e), in the red flour beetle, Tribolium castaneum, we performed real-time PCR to analyze its developmental and tissue-specific expression, and utilized immunohistochemistry to identify the localization of the TcY-e protein in adult cuticle...
March 15, 2015: Developmental Biology
Ian C Kutch, Hasan Sevgili, Tyler Wittman, Kenneth M Fedorka
As temperatures change, insects alter the amount of melanin in their cuticle to improve thermoregulation. However, melanin is also central to insect immunity, suggesting that thermoregulatory strategy may indirectly impact immune defense by altering the abundance of melanin pathway components (a hypothesis we refer to as thermoregulatory-dependent immune investment). This may be the case in the cricket Allonemobius socius, where warm environments (both seasonal and geographical) produced crickets with lighter cuticles and increased pathogen susceptibility...
October 15, 2014: Journal of Experimental Biology
Iryna Shakhmantsir, Nicole L Massad, Jennifer A Kennell
BACKGROUND: Insect pigmentation is a phenotypically plastic trait that plays a role in thermoregulation, desiccation tolerance, mimicry, and sexual selection. The extent and pattern of pigmentation of the abdomen and thorax in Drosophila melanogaster is affected by environmental factors such a growth temperature and access to the substrates necessary for melanin biosynthesis. This study aimed to determine the effect of nutritional status during development on adult pigmentation and test whether nutrient sensing through the Insulin/IGF and target of rapamycin (TOR) pathways regulates the melanization of adult cuticle in Drosophila...
March 2014: Developmental Dynamics: An Official Publication of the American Association of Anatomists
Christopher John Vavricka, Qian Han, Prajwalini Mehere, Haizhen Ding, Bruce M Christensen, Jianyong Li
Differences in the metabolism of tyrosine between insects and mammals present an interesting example of molecular evolution. Both insects and mammals possess fine-tuned systems of enzymes to meet their specific demands for tyrosine metabolites; however, more homologous enzymes involved in tyrosine metabolism have emerged in many insect species. Without knowledge of modern genomics, one might suppose that mammals, which are generally more complex than insects and require tyrosine as a precursor for important catecholamine neurotransmitters and for melanin, should possess more enzymes to control tyrosine metabolism...
February 2014: Insect Science
Kenneth M Fedorka, Emily K Copeland, Wade E Winterhalter
To improve thermoregulation in colder environments, insects are expected to darken their cuticles with melanin via the phenoloxidase cascade, a phenomenon predicted by the thermal melanin hypothesis. However, the phenoloxidase cascade also plays a significant role in insect immunity, leading to the additional hypothesis that the thermal environment indirectly shapes immune function via direct selection on cuticle color. Support for the latter hypothesis comes from the cricket Allonemobius socius, where cuticle darkness and immune-related phenoloxidase activity increase with latitude...
November 1, 2013: Journal of Experimental Biology
D A Roff, D J Fairbairn
Melanism is an important component of insect cuticle and serves numerous functions that enhance fitness. Despite its importance, there is little information on its genetic basis or its phenotypic and genetic correlation with fitness-related traits. Here, we examine the heritability of melanism in the wing dimorphic sand cricket and determine its phenotypic and genetic correlation with wing morphology, gonad mass and size of the dorso-longitudinal muscles (the principle flight muscles). Previously demonstrated trade-offs among these traits are significant factors in the evolution of life history variation...
July 2013: Journal of Evolutionary Biology
Panchanathan Manivasagan, Jayachandran Venkatesan, Kannan Sivakumar, Se-Kwon Kim
Melanins are enigmatic pigments that are produced by a wide variety of microorganisms including several species of bacteria and fungi. Melanins are biological macromolecules with multiple important functions, yet their structures are not well understood. Melanins are frequently used in medicine, pharmacology, and cosmetics preparations. Melanins also have great application potential in agriculture industry. They have several biological functions including photoprotection, thermoregulation, action as free radical sinks, cation chelators, and antibiotics...
October 2013: World Journal of Microbiology & Biotechnology
Najealicka Armstrong, Malaisamy Ramamoorthy, Delina Lyon, Kimberly Jones, Atanu Duttaroy
Silver nanoparticles (AgNPs), like almost all nanoparticles, are potentially toxic beyond a certain concentration because the survival of the organism is compromised due to scores of pathophysiological abnormalities past that concentration. However, the mechanism of AgNP toxicity remains undetermined. Instead of applying a toxic dose, we attempted to monitor the effects of AgNPs at a nonlethal concentration on wild type Drosophila melanogaster by exposing them throughout their development. All adult flies raised in AgNP doped food showed that up to 50 mg/L concentration AgNP has no negative influence on median survival; however, these flies appeared uniformly lighter in body color due to the loss of melanin pigments in their cuticle...
2013: PloS One
Liang Qiao, Yuanhao Li, Gao Xiong, Xiaofan Liu, Songzhen He, Xiaoling Tong, Songyuan Wu, Hai Hu, Rixin Wang, Hongwei Hu, Lushi Chen, Li Zhang, Jie Wu, Fangyin Dai, Cheng Lu, Zhonghuai Xiang
Catecholamine metabolism plays an important role in the determination of insect body color and cuticle sclerotization. To date, limited research has focused on these processes in silkworm. In the current study, we analyzed the interactions between catecholamines and melanin genes and their effects on the pigmentation patterns and physical properties of sclerotized regions in silkworm, using the melanic mutant melanism (mln) silkworm strain as a model. Injection of β-alanine into mln mutant silkworm induced a change in catecholamine metabolism and turned its body color yellow...
2012: PloS One
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