Production Of Melanin Pigment Research Articles

The Production of Melanin Pigments From Some Pathogenic Fungi in Response to L-Tyrosine Under Laboratory Conditions

Background: This study aims to evaluate response of plant pathogenic fungi to the amino acid L-tyrosine through the production of melanin. Methods: Potato dextrose broth (PDB) and PDB with 1% L-tyrosine were used for current evaluation. Melanin was produced, extracted and characterized from pathogenic fungi that infected rice in Iraq. Results: Results indicated that L-tyrosine was used as a source of the precursor by fungi belonging to Bipolaris. spicifera R15, Alternaria. alternata R18, Exserohilum. rostratum R19, Alternaria. alternate R20, and Alternaria. tenuissima R23, also produced higher levels of condensed black pigment. While, fungi like Nigrospora oryzae R9, Curvularia lunata R7, C lunata R21 and A tenuissima R24 were used more than one pathway for melanin production. UV transmittance increased significantly from 600 nm to 300 nm whereas absorbance decreased at 260 and 280 nm for all of the studied fungi. Analysis of FT-IR spectra and related assignment group of resolved that melanin extracted from B. spicifera R15 (3408.22), A. alternate R20 (3392.79), and A. tenuissima R24 (3387). Wavenumbers 2924 cm−1 and 2854 cm−1 were found in E. rostratum R19, A. alternative R20, and A. tenuissima R24 melanin extracts, respectively. Meanwhile, B. spicifera R15 revealed a single peak at 2929 cm−1. 3007.02 cm−1, 3072.6 cm−1, 3074.53 cm−1, 2920.3 cm−1, 2704.2 cm−1, and 1861.31 cm−1 are also assigned wavenumbers. Conclusion: Melanin-like pigments are produced via L-tyrosine-dependent and independent pathways. All colors extracted from fungal hyphae were morphologically and chemically identical to melanin. A UV scan and FT-IR analysis revealed differences in the physical appearance of building units and the structure of the melanin pigment produced by plant pathogenic fungi.

Small Peptide Derived from SFRP5 Suppresses Melanogenesis by Inhibiting Wnt Activity.

Melanocytes, located in the epidermis' basal layer, are responsible for melanin pigment production, crucial for skin coloration and protection against UV radiation-induced damage. Melanin synthesis is intricately regulated by various factors, including the Wnt signaling pathway, particularly mediated by the microphthalmia-associated transcription factor (MITF). While MITF is recognized as a key regulator of pigmentation, its regulation by the Wnt pathway remains poorly understood. This study investigates the role of Sfrp5pepD, a peptide antagonist of the Wnt signaling pathway, in modulating melanogenesis and its potential therapeutic implications for pigmentary disorders. To tackle this issue, we investigated smaller peptides frequently utilized in cosmetics or pharmaceuticals. Nevertheless, there is a significant scarcity of reports on peptides associated with melanin-related signal modulation or inhibiting melanin production. Results indicate that Sfrp5pepD effectively inhibits Wnt signaling by disrupting the interaction between Axin-1 and β-catenin, thus impeding downstream melanogenic processes. Additionally, Sfrp5pepD suppresses the interaction between MITF and β-catenin, inhibiting their nuclear translocation and downregulating melanogenic enzyme expression, ultimately reducing melanin production. These inhibitory effects are validated in cell culture models suggesting potential clinical applications for hyperpigmentation disorders. Overall, this study elucidates the intricate interplay between Wnt signaling and melanogenesis, highlighting Sfrp5pepD as a promising therapeutic agent for pigmentary disorders. Sfrp5pepD, with a molecular weight of less than 500 Da, is anticipated to penetrate the skin unlike SFRPs. This suggests a strong potential for their use as cosmetics or transdermal absorption agents. Additional investigation into its mechanisms and clinical significance is necessary to enhance its effectiveness in addressing melanin-related skin conditions.

Anti-vitiligo effect of Thespesia populnea L. bark against Tyrosinase enzyme using In-silico model

Background: Siddha medicine is one among the popular traditional systems of medicine in treating various diseases. Vitiligo is a primary autoimmune de-pigmentary disorder. Generally, melanin pigment production is diminished in vitiligo. By improving tyrosinase activity, melanogenesis can be achieved in vitiligo. Hence the phytocomponents which bind with the target Tyrosinase enzyme, act as a potential treatment for vitiligo. Objective: The objective of this study is to find the lead molecules that bind with these core bio active amino acid residues namely His 190, His54, His63, His194, His38 and His216.These bioactive residues mediates the enzymatic action of tyrosinase enzyme and tends to enhance the action of tyrosinase enzyme which improves melanogenesis. Methods: Auto dock program was used for the molecular docking studies against Tyrosinase enzyme. Results: From reported data of the herb, the phytochemicals Myricetin reveals highiest of 4 interactions with the core active amino acid residues of the target Tyrosinase enzyme.Second highiest level is reached by the compounds such as Catechin, Apigenin and Cinnamic acid with the 3 interactions with the active site . Gallic acid and Quercetin reveal 2 interactions over the target enzyme. From the results of docking study of the herb, the leads such as Catechin, Myricetin, Apigenin and Cinnamic acid possess 3-4 interactions with core target amino acids of Tyrosinase enzyme and helps in treatment and management of vitiligo. Conclusion: These phytochemicals exhibit anti-vitiligo activity by harmonising the action of tyrosinase enzyme in vitiligo treatment. Further clinical trials need to be performed for identifying the efficacy and effectiveness of Thespesia populnea in the treatment and management of vitiligo.

Bioproduction and characterization of melanin pigment produced by the fungal strain Gliocephalotrichum sp. DSGB2

Introduction and Aim: The biosynthetic method of naturally occurring pigment melanin production has become a predominant technique in recent years owing to its cost-effectiveness, low chemical usage, and reduced purification procedure. This study aimed to investigate the significant production, characterization, and biological applications of fungal melanin pigment. Materials and Methods: Melanin production in Gliocephalotrichum sp. DSGB2 strain was carried out by submerged fermentation in tyrosine broth and further purified by acidification and precipitation methods. The purified melanin was characterized by analytical methods such as ultraviolet-visible absorbance, TLC, FTIR spectroscopy, and LC-MS. The DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging analysis was performed to evaluate antioxidant properties of melanin. Results: Pigment was confirmed as melanin based on tyrosinase enzyme assay, UV-visible spectroscopy absorbance, TLC, FTIR, and LC-MS analysis. The biosynthesis of melanin was optimized by varying the culture conditions, and the highest yield was obtained under pH 6 at 30ºC. The strain produced about 3.82 gL-1 of melanin in 5 days under optimum conditions and exhibited antioxidant activity. Conclusion: The study provides new ideas into the biosynthesis of water-soluble melanin by the fungal strain Gliocephalotrichum sp. DSGB2 has broad potential applications as an efficient biomaterial in the biopolymer, pharmaceutical sectors, cosmetic, and environmental.

Production and characterization of melanin pigment from black fungus Curvularia soli AS21 ON076460 assisted gamma rays for promising medical uses

Owing to the growing need for natural materials in different fields, studying melanin production from biological sources is imperative. In the current study, the extracellular melanin pigment was produced by the fungus Curvularia soli AS21 ON076460. The factors that affect the production of melanin were optimized by the Plackett-Burman design (P-BD). The effect of gamma irradiation on melanin productivity was investigated. The maximum melanin yield (3.376 mg/L) was elicited by a stimulus of gamma irradiation at 1.0 kGy. The results evoked that, Curvularia soli AS21 ON076460 melanin exhibited excellent antimicrobial activity against all tested bacteria and fungi. Klebsiella pneumoniae ATCC 13883 and P. digitatum were mostly affected by melanin registering the inhibition zone diameters of 37.51 ± 0.012 and 44.25 ± 0.214 mm, respectively. Moreover, Curvularia soli AS21 ON076460 melanin indicated a significant antiviral efficacy (77% inhibition) of Herpes simplex virus (HSV1). The melanin pigment showed antioxidant activities with IC50 of 42 ± 0.021 and 17 ± 0.02 µg/mL against DPPH and NO, respectively. Melanin had cytotoxic action against human breast cancer and skin cancer cell lines (Mcf7and A431) as well as exerting a low percentage of cell death against normal skin cell lines (Hfb4). Melanin was effective in wound management of human skin cells by 63.04 ± 1.83% compared with control (68.67 ± 1.10%). The novelty in the study is attributed to the possibility of using gamma rays as a safe method in small economic doses to stimulate melanin production from the fungi that have been isolated. In summary, melanin produced from fungi has significant biological activities that encourage its usage as a supportive medical route.

Efficient production and characterization of melanin from Thermothelomyces hinnuleus SP1, isolated from the coal mines of Chhattisgarh, India.

In the present study, fungi were isolated and screened from barren land in south-eastern Coalfields limited (SECL) in Chhattisgarh, India. Out of 14 isolated fungi, only three fungal isolates exhibited pigmentation in screening studies. The isolated fungal strain SP1 exhibited the highest pigmentation, which was further utilized for in vivo production, purification, and characterization of melanin pigment. The physical and chemical properties of the fungal pigment showed insolubility in organic solvents and water, solubility in alkali, precipitation in acid, and decolorization with oxidizing agents. The physiochemical characterization and analytical studies of the extracted pigment using ultraviolet-visible spectroscopy and Fourier transform infrared (FTIR) confirmed it as a melanin pigment. The melanin-producing fungus SP1 was identified as Thermothelomyces hinnuleus based on 18S-rRNA sequence analysis. Furthermore, to enhance melanin production, a response surface methodology (RSM) was employed, specifically utilizing the central composite design (CCD). This approach focused on selecting efficient growth as well as progressive yield parameters such as optimal temperature (34.4°C), pH (5.0), and trace element concentration (56.24 mg). By implementing the suggested optimal conditions, the production rate of melanin increased by 62%, resulting in a yield of 28.3 mg/100 mL, which is comparatively higher than the actual yield (17.48 ± 2.19 mg/100 mL). Thus, T. hinnuleus SP1 holds great promise as a newly isolated fungal strain that could be used for the industrial production of melanin.

Case Report: Cutaneous melanocytic schwannoma with concomitant melanocytoma in a canine

Schwannoma is a nerve sheath tumour arising from differentiated Schwann cells, and melanocytic schwannoma (MS) is a rare variant where the Schwan cells produce melanin pigment. MS is typically associated with spinal nerve roots and there have been only ~20 reports of cutaneous or subcutaneous MS to-date in humans. In canines, there have only been two reports of MS, both associated with spinal root nerves. In this report, we describe a 7-year-old Weimaraner cross breed dog that presented with two pigmented lesions on the eyelids. The lesions were surgically removed and histological analysis revealed well-circumscribed, non-encapsulated, expansile, neoplasms that were displacing most of the dermis and adnexa. The first lesion was composed of spindloid cells arranged in short interlacing streams with large amounts of pale eosinophilic cytoplasm that sometimes contained fine melanin granules. In areas there were spindle cells arranged in verocay bodies which led to a diagnosis of MS. In contrast, the second lesion was composed of polygonal cells arranged in thick sheets with large amounts of pale eosinophilic cytoplasm that sometimes contained fine melanin granules. The diagnosis was melanocytoma (which is one of the macroscopic differential diagnoses for MS). Whilst melanocytoma is a commonly occurring cutaneous lesion in canines and surgical removal is considered curative, due to little being known about MS in dogs, the outcome remained guarded, as MS in humans has an unpredictable nature, and recurrence and metastasis have been reported.

Synthesis, Anti-Tyrosinase Activity, and Spectroscopic Inhibition Mechanism of Cinnamic Acid-Eugenol Esters.

Tyrosinase plays crucial roles in mediating the production of melanin pigment; thus, its inhibitors could be useful in preventing melanin-related diseases. To find potential tyrosinase inhibitors, a series of cinnamic acid-eugenol esters (c1~c29) was synthesized and their chemical structures were confirmed by 1H NMR, 13C NMR, HRMS, and FT-IR, respectively. The biological evaluation results showed that all compounds c1~c29 exhibited definite tyrosinase inhibitory activity; especially, compound c27 was the strongest tyrosinase inhibitor (IC50: 3.07 ± 0.26 μM), being ~4.6-fold stronger than the positive control, kojic acid (IC50: 14.15 ± 0.46 μM). Inhibition kinetic studies validated compound c27 as a reversible mixed-type inhibitor against tyrosinase. Three-dimensional fluorescence and circular dichroism (CD) spectra results indicated that compound c27 could change the conformation and secondary structure of tyrosinase. Fluorescence-quenching results showed that compound c27 quenched tyrosinase fluorescence in the static manner with one binding site. Molecular docking results also revealed the binding interactions between compound c27 and tyrosinase. Therefore, cinnamic acid-eugenol esters, especially c27, could be used as lead compounds to find potential tyrosinase inhibitors.

Ocular and Oculocutaneous Albinism: Pathogenesis, Diagnosis, and Treatment

Oculocutaneous albinism (OCA) is the common name of a group of hereditary diseases accompanied by disorders in the production of melanin pigment and affect the hair, skin, and eyes. Besides being responsible for pigmentation, melanin acts as a barrier against the harmful effects of ultraviolet (UV) light. Individuals with pigment deficiency are at risk for the development of disorders such as visual impairment and nystagmus, as well as the development of skin cancer depending on the type of disease and therefore the degree of pigmentation. The diagnosis of OCA is mainly based on dermatological and biomicroscopic examination. Although there is no specific treatment method for ocular or oculocutaneous albinism today, treatments to improve patients' quality of life and protective measures are important.

Deciphering the Effect of Light Wavelengths in Monilinia spp. DHN-Melanin Production and Their Interplay with ROS Metabolism in M. fructicola.

Pathogenic fungi are influenced by many biotic and abiotic factors. Among them, light is a source of information for fungi and also a stress factor that triggers multiple biological responses, including the activation of secondary metabolites, such as the production of melanin pigments. In this study, we analyzed the melanin-like production in in vitro conditions, as well as the expression of all biosynthetic and regulatory genes of the DHN-melanin pathway in the three main Monilinia species upon exposure to light conditions (white, black, blue, red, and far-red wavelengths). On the other hand, we analyzed, for the first time, the metabolism related to ROS in M. fructicola, through the production of hydrogen peroxide (H2O2) and the expression of stress-related genes under different light conditions. In general, the results indicated a clear importance of black light on melanin production and expression in M. laxa and M. fructicola, but not in M. fructigena. Regarding ROS-related metabolism in M. fructicola, blue light highlighted by inhibiting the expression of many antioxidant genes. Overall, it represents a global description of the effect of light on the regulation of two important secondary mechanisms, essential for the adaptation of the fungus to the environment and its survival.

Signatures of Admixture and Genetic Uniqueness in the Autochthonous Greek Black Pig Breed Deduced from Gene Polymorphisms Affecting Domestication-Derived Traits.

The Greek Black Pig (or Greek Pig) is the only recognized autochthonous pig breed raised in Greece, usually in extensive or semi-extensive production systems. According to its name, the characteristic breed coat color is solid black. In this study, with the aim to start a systematic genetic characterization of the Greek Black Pig breed, we investigated polymorphisms in major genes well known to affect exterior and production traits (MC1R, KIT, NR6A1, VRTN and IGF2) and compared these data with population genetic information available in other Mediterranean and Western Balkan pig breeds and wild boars. None of the investigated gene markers were fixed for one allele, suggesting that, in the past, this breed experienced introgression from wild boars and admixture from cosmopolitan pig breeds, enriching the breed genetic pool that should be further investigated to design appropriate conservation genetic strategies. We identified a new MC1R allele, containing two missense mutations already reported in two other independent alleles, but here present in the same haplotype. This allele might be useful to disclose biological information that can lead to better understanding the cascade transmission of signals to produce melanin pigments. This study demonstrated that autochthonous genetic resources can be an interesting reservoir of unexpected genetic variants.

Isolation, Culture, and Transfection of Melanocytes.

Located in the basal epidermis and hair follicles, melanocytes of the integument are responsible for its coloration through production of melanin pigments. Melanin is produced in a type of lysosome-related-organelle (LRO) called the melanosome. In humans, this skin pigmentation acts as an ultraviolet radiation filter. Abnormalities in the division of melanocytes are quite common, with potentially oncogenic growth usually followed by cell senescence producing benign naevi (moles), or occasionally, melanoma. Therefore, melanocytes are a useful model for studying both cellular senescence and melanoma, as well as many other aspects of biology such as pigmentation, organelle biogenesis and transport, and the diseases affecting these mechanisms. Melanocytes for use in basic research can be obtained from a range of sources, including surplus postoperative skin or from congenic murine skin. Here we describe methods to isolate and culture melanocytes from both human and murine skin (including the preparation of mitotically inactive keratinocytes for use as feeder cells). We also describe a high-throughput transfection protocol for human melanocytes and melanoma cells. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Primary explantation of human melanocytic cells Basic Protocol 2: Preparation of keratinocyte feeder cells for use in the primary culture of mouse melanocytes Basic Protocol 3: Primary culture of melanocytes from mouse skin Basic Protocol 4: Transfection of human melanocytes and melanoma cells.

In Silico Study of Naringenin as Melanogenesis Inducer in Vitiligo

Introduction: Vitiligo is a pigmentation disorder characterized by loss of skin color (depigmentation) due to melanocyte dysfunction and loss. Melanocytes produce melanin pigment through a melanogenesis process. Melanocyte survival and melanogenesis process are influenced by Microphthalmia Associated- Transcription Factor (MITF) and several proteins, including WNT, β-catenin, tyrosinase, Tyrosinase- Related Protein-1 (TRP1), and Tyrosinase-Related Protein-2 (TRP2). The current therapy for vitiligo is still unsatisfactory. Naringenin is one of Rhizophora mucronata compound, one type of mangrove plant often found in the eastern coastal area of Surabaya City. Objective: To investigate the naringenin’s potency in melanogenesis and to predict the pharmacokinetics or toxicity of naringenin by in silico study. Methods: This is a computational study using a molecular docking method to observe the interaction of naringenin with WNT, β-catenin, MITF, tyrosinase, TRP-1, and TRP-2 proteins. Pharmacokinetic or toxicity prediction of naringenin using the pkCSM method. Psoralen was used as a control. Results: Naringenin binds to all these proteins in the same region as psoralen, indicating that naringenin can stimulate melanogenesis. Naringenin has lower binding energy than psoralen on all proteins (except β-catenin), indicating that naringenin's interaction with these proteins is stronger than psoralen. Pharmacokinetic and toxicity predictions show that naringenin has good absorption or permeation, is not mutagenic, is not hepatotoxic, and does not cause skin sensitization. Conclusion: This computational study concludes that naringenin has melanogenesis inducer potency and good pharmacokinetics.

Malignant Melanotic Nerve Sheath Tumors: A Review of Clinicopathologic and Molecular Characteristics.

Malignant melanotic nerve sheath tumor (MMNST) which was formerly known as melanocytic schwannoma, is an uncommon aggressive type of nerve sheath tumor. It originates from nerve roots with clonal Schwann cell proliferation and melanin pigment production. MMNST which was once thought to be a benign tumor is now considered a malignant disease based on the latest 2020 World Health Organization classification of soft tissue tumors. Interestingly, despite the histologic features appearing benign with a low proliferation index, the clinical course of this tumor is malignant, which was demonstrated in case series with high rate of recurrences and metastasis. This tumor can occur sporadically or in patients with an underlying familial predisposition syndrome called, Carney's complex. Affected patients will often harbor a germline mutation in the PRKAR1A gene. MMNST can be histologically difficult to distinguish from malignant melanoma, other melanocytic tumors, and Schwannoma. Having a better understanding of its clinic pathologic characteristics and associated conditions is essential in properly diagnosing and managing affected individuals. This includes the possible need for genetic testing to detect germline mutations, genetic counseling, and surveillance according to published recommendations. In this article, we summarize the clinic pathologic and molecular features of MMNST and discuss what is known about its molecular biology and its associations with predisposing conditions. The review was conducted through an extensive PubMed search using keywords then relevant publications were selected.

Alloferon improves the growth performance and developmental time of mealworms (Tenebrio molitor)

Mealworms (Tenebrio molitor) are important food sources for reptiles, birds, and other organisms, as well as for humans. Due to their outstanding nutritional value, mealworms are in high demand as an alternative food source and are the subject of widespread curiosity. However, the slow growth and low survival rate of mealworms cause problems for mass production. Since alloferon, a synthetic peptide, showed long-term immunological effects on mealworms, we hypothesized that alloferon would function as a growth promoter to maximize mealworm production. We discovered that the overall weight of the alloferon-containing gelatin diet group was 39.5-90% heavier, and the development time of the experimental group was shortened up to 20.6-39.6% than the control group. In addition, 300 nM alloferon significantly boosted cell proliferation of Sf9 cells (insect cells) only after six days of the treatment. Also, we noticed that two proteins were induced in alloferon fed mealworm body tissue and found that one of the proteins was phenoloxidase 1, which may be responsible for increasing growth rate by regulating the production of melanin pigments. Overall, these findings have potential implications in mealworm insect farming because alloferon may foster a sustainable food supply industry.

Evaluation the efficacy of some culture media in melanin production by Cryptococcus neoformans

Abstract Cryptococcus neoformans is a capsule containing yeast pathogen, commonly found in urban environments that causes Cryptococcosis which is a worldwide fungal disease. The current study. This study was aimed to compare the ability of some culture media to detect melanin production by C. neoformans isolates. A total of 202 clinical samples obtained from patients suffering from meningitis, during the period from September 2020 through April 2021. The isolation and identification results revealed that 179 (88.61%) samples were positive for yeast growth. 29 (14.35%). Twenty-nine from 202 of samples were C. neoformans according to the morphological characteristics and the biochemical tests, and 150 (74.25%) samples for Candida spp. All C. neoformans isolates produced blue dry colonies on cryptococcus differential agar. Several differential media were used for the purpose of testing the ability of C. neoformans to produce melanin pigment, these includes: Niger seed agar medium (Staib’s Agar), and the colonies of C. neoformans appeared on this medium in a brown color after 2–5 days of incubation, Tobacco agar where those colonies gave a dark brown color after 48–72 h, and Methyldopa agar which was the best medium for the detection of melanin production because the results were faster from the other media, interestingly the colonies can produce the pigment and can growth very fast within 24hr.

In Vitro Reconstitution of the Melanin Pathway's Catalytic Activities Using Tyrosinase Nanoparticles.

The melanogenesis pathway is characterized by a series of reactions catalyzed by key enzymes, such as tyrosinase (TYR), tyrosinase-related protein 2 (TYRP2), and tyrosinase-related protein 1 (TYRP1), to produce melanin pigment. However, in vitro studies of the catalytic activity were incomplete because of a lack of commercially available enzyme substrates, such as dopachrome. Herein, human recombinant intra-melanosomal domains of key enzymes were produced in Trichoplusia ni (T. ni) larvae and then purified using a combination of chromatography techniques in catalytically active form. Using Michaelis-Menten kinetics, the diphenol oxidase activity of tyrosinase achieved the maximum production of native dopachrome at 10 min of incubation at 37 °C for TYR immobilized to magnetic beads (TYR-MB). The presence of dopachrome was confirmed spectrophotometrically at 475 nm through HPLC analysis and in the TYRP2-catalyzed reaction, yielding 5,6-dihydroxyindole-2-carboxylic acid (DHICA). In the TYRP1-driven oxidation of DHICA, the formation of 5,6-indolequinone-2-carboxylic acid (IQCA) was confirmed at ~560 nm. This is the first in vitro reconstitution of the reactions from the melanogenic pathway based on intra-melanosomal domains. In the future, this approach could be used for quantitative in vitro analysis of the melanin pathway, biochemical effects associated with inherited disease-related mutations, and drug screens.

Antioxidant activities from melanin pigment produced by marine actinobacterium of Streptomyces species.

Melanin is macromolecules which have been developed while oxidative polymerization of phenolic compounds. It has been found that the majority of marine organisms produce melanin pigment. To obtain the melanin from marine actinobacteria and their biological properties are studied. Isolation and identification of marine actinobacteria were carried out using the media of ISP-1, ISP-7. Spore chain morphology, chemotaxonomic characteristics were also analyzed by the International Streptomyces Project. The antioxidant activities of DPPH, lipid peroxide using actinobacterial melanin were determined. The Streptomyces species have the capacity to produce melanin pigments and it shows potential antioxidant properties. When DPPH concentrations were compared with the ascorbic acid standard, the melanin of 150 μg/ml showed 93.47% of scavenging. The present study was concluded that melanin pigment obtained from marine actinobacterium of Streptomyces species has potential antioxidant activities and these components might be useful to pharmaceutical industries.

Melanin pigments from sediment-associated Nocardiopsis sp. marine actinobacterium and antibacterial potential.

To extract the melanin pigment from marine microbes and their biological potential, the present study was done. Isolation and identification of the melanin-producing Nocardiopsis sp. were obtained from the sediment samples. Zone of inhibition and minimal inhibitory concentration test was performed using melanin. Melanin was extracted from sediment-associated marine Nocardiopsis sp. In the present study, marine actinobacterium was identified by the conventional method, and the isolate was identified as Nocardiopsis sp. Melanin was extracted, and antibacterial activities were performed against different pathogens and the highest zone of inhibition is more in the E. coli while related to another two species. From previous observation done by Fu et al., they have said that marine actinobacteria have the ability of antimicrobial activity, which is very much helpful in producing the potential antimicrobial drugs this was similar to our study that marine actinobacteria have the capability to produce melanin pigment, and at the same time, it helps as to show the antibacterial activity. We concluded that melanin is produced by the Nocardiopsis sp. We also found that melanin extracted from the Nocardiopsis sp. of marine actinobacterium also has an antibacterial effect.

Abnormal overexpression of SoxD enhances melanin synthesis in the Ursa mutant of Bombyx mori

The pigment and structural color of insects play crucial roles in body protection, ecological adaptation, and signal communication. Epidermal melanization is a common and main coloring pattern, which results in broad phenotypic diversity. Melanin is one of the compounds contributing to dark brown-black pigmentation, which is synthesized from dopamine and tyrosine by the melanin metabolism pathway. The Ursa mutant of the silkworm Bombyx mori is a body-color mutant characterized by excessive melanin pigmentation in the larval epidermis. However, the exact gene responsible for this phenotype remains unclear. Here, we performed positional cloning of the gene responsible for Ursa, which was mapped to an 83-kb region on chromosome 14. The genomic region contains a protein-coding gene encoding a transcription factor, which was designated BmSoxD. The mutation site was determined by analysis of nucleotide sequences of the genomic region corresponding to BmSoxD, which identified a 449-bp transposable sequence similar to that of the B. mori transposon Helitron inserted into the sixth intron. BmSoxD was dramatically overexpressed in the epidermis of Ursa at the end of the molting stage compared with that of wild-type B. mori. Overexpression of BmSoxD led to upregulation of genes involved in the melanin metabolism pathway, whereas knocking down BmSoxD via small interfering RNAs blocked melanin pigment production in the larval epidermis. These data indicate that the mutation in BmSoxD is responsible for the Ursa mutant phenotype. We propose that the transposable sequence insertion causes abnormal overexpression of BmSoxD at the molting stage in the Ursa mutant, resulting in excessive melanin synthesis and its accumulation in epidermal cells.