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    Effect of Nrg1 Repressor on NTH1 Transcription and Molecular Docking of Nrg1 on NTH1 Promoter
    (Univ Indonesia, 2019) Genc, Tulay Turgut; Dogan, Gamze
    The amount of intracellular trehalose increases in response to environmental stress in yeast (Saccharomyces cerevisiae). When that stress is terminated, the accumulated trehalose rapidly degrades into glucose rapidly. Synthesis of trehalose is fulfilled by the Trehalose Phosphate Synthase (TPS) enzyme complex, whereas the degradation of trehalose is done by the neutral trehalase enzyme. Under different stress conditions, transcription of the NTH1 gene is activated and Stress Response Elements (STRE) are required for this activation. Nrg1 protein can bind promoters including STRE and PDS elements. Because of the presence of three possible Nrg1 repressor binding sites on the NTH1 promoter, the NTH1 gene may be regulated by the Nrg1 repressor. In order to test this hypothesis,.nrg1 mutant yeast and its isogenic wildtype yeast strain were used to analyze the transcriptional activation of the NTH1 gene under nitrogen starving conditions. Nth1 transcription of the mutant yeast was seven-fold higher than that of the wild-type under growth conditions, and was not changed during nitrogen starvation. The protein-DNA docking analysis also supported the possibility of Nrg1 binding to the NTH1 promoter. These results revealed that NTH1 gene expression is constitutive in the absence of the Nrg1 repressor protein, hence the transcription of NTH1 is repressed by the Nrg1 protein.
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    Hemocytes: Central drivers of antimicrobial peptide expression and immune proteins in both cellular and humoral responses of Galleria mellonella
    (Wiley, 2025) Kaya, Serhat; Genc, Tulay Turgut; Gunay, Melih
    Insects have an effective innate immune system that includes both cellular and humoral responses for defense against pathogens. Antimicrobial peptides like gallerimycin and galiomycin, as well as immune proteins like hemolin, are the important effectors of the humoral immune response in Galleria mellonella L. (Lepidoptera:Pyralidae). Encapsulation, on the contrary, is one of the important cellular immune responses. This study investigated the tissue-specific expression of an immune effector in G. mellonella larvae after injection with Candida albicans (C.P. Robin) (Ascomycota: Debaryomycetaceae) and silica beads. The gene expression of gallerimycin, galiomycin, and hemolin was examined in total larvae, hemocytes, and fat bodies at 4 and 24 h following injection. Our findings indicate that hemocytes serve as the main site for AMP synthesis, especially after bead injection, implying a more effective immune recognition mechanism relative to pathogen injection. Furthermore, we detected higher hemolin expression in hemocytes than fat tissue, indicating its role in hemocyte-mediated immune responses. Encapsulation rates were also evaluated in bead-injected larvae. At 4 h post-injection, most beads were weakly encapsulated, whereas by 24 h, the majority were strongly encapsulated, reflecting a time-dependent maturation of the immune response. These results show that G. mellonella has a unique immune system, with hemocytes playing a key role in regulating AMP production and immune responses during infection. This study provides deeper insights into the molecular and cellular mechanisms of insect immunity, positioning G. mellonella as a valuable model for studying host-pathogen interactions.
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    Immune activation by Ziziphus jujuba in Galleria mellonella: challenge-specific and temporal dynamics of humoral immune responses
    (Cambridge Univ Press, 2026) Genc, Tulay Turgut; Kaya, Serhat; Gunay, Melih
    The immunomodulatory effects of Ziziphus jujuba Mill. fruit extracts were investigated using Galleria mellonella as an insect immune model. The expression of antimicrobial peptides, hemolin, phenoloxidase genes (PO-I and PO-II), and enzyme activity was measured in response to Candida albicans, silica beads, and Z. jujuba fruit extract. Responses were found to be stimulus- and time-dependent. Gallerimycin and galiomycin, key antimicrobial peptides, exhibited distinct expression patterns, with gallerimycin showing a more pronounced response to pathogens and beads. The Z. jujuba extract stimulated an early but balanced immune activation, likely due to its bioactive compounds. Hemolin expression varied between larvae and haemocytes depending on the type and duration of the challenge, supporting its role in immune recognition and opsonisation. Phenoloxidase activity and gene expression were also enhanced, supporting their role in promoting melanisation processes. Docking analyses suggested that hemolin contributes to phenoloxidase activation by stabilising PO-I and interacting with the phenoloxidase-activating factor-1-like protein (PAP1). The findings suggest that Z. jujuba extract effectively modulates immune responses, promoting enhanced protection while maintaining immune balance. GC-MS analysis revealed multiple bioactive compounds potentially contributing to immune modulation. This study highlights the significant immunomodulatory effects of Z. jujuba fruit extract on the immune system of G. mellonella. The findings suggest its potential as a natural immunostimulant and warrant further investigation of the underlying molecular mechanisms and bioactive components.
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    Internal transcribed spacer (ITS) sequence-based identification of yeast biota on pomegranate surface and determination of extracellular enzyme profile
    (Univ Sebelas Maret, 2020) Genc, Tulay Turgut; Gunay, Melih
    Yeasts are the most significant organisms to produce fermented products from different types of fruits such as grape, strawberry and pomegranate. The native yeasts on these fruits contribute to beverages' quality and aroma during fermentation. Pomegranate is used in fruit juice and wine production because of high antioxidant characteristic. In order to determine yeast microbiota on the pomegranate fruits collected from Gallipoli (Gelibolu), Canakkale-Turkey, ITS-5.8S rDNA gene region have been utilized. Also, phylogenetic relationships among identified yeast species were assigned by using sequences of ITS-5.8S rDNA gene region. In addition, extracellular enzyme activity of identified yeast strains was detected by using API-ZYM. Kluyveromyces lactis, Aureobasidium pullulans, Hanseniaspora uvarum, Candida zeylanoides, Kwoniella sp., and Metschnikowia pulcherrima and Metschnikowia ziziphicola yeast species were identified on pomegranate surface. Phylogenetic analysis, carried out in ITS-5.8S rDNA gene region of identified yeast strains, revealed the presence of five clades. Kwoniella sp., H. uvarum, M. pulcherrima, and Kl. lactis yeast strains revealed high leucine arylamidase activity. Also valine arylamidase activity was determined in M. pulcherrima and Kl. lactis yeast species. Acid phosphatase activity was determined in H. uvarum and K. lactis yeast species. Uncultured Kwoniella sp. and H. uvarum yeast species displayed high beta-galactosidase and beta-glucosidase activities, respectively.
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    Non-Saccharomyces yeasts diversity on grape berries and molecular characterization of Starmerella bacillaris yeasts strains having high invertase activity
    (Natl Inst Science Communication-Niscair, 2022) Genc, Tulay Turgut
    The diversity of yeast species on grape berries changes depending on various factors. Determination of indigenous yeast intensity and diversity on grape berries is important for increasing the sensory characteristics of wine as well as fermentation efficiency. The natural yeast biota of grape berries affects wine flavour and quality by producing some secondary metabolites and hydrolytic enzymes. Despite the application of different nonconventional yeasts in food and fermentation industries, many significant researches are conducted in finding and improving the new strains having industrially important enzyme activities. Invertase enzyme has a vital role in the food industry in which it increases the sweetness of food without crystallizing them. Here, we studied yeast diversity in grape berries from selected localities and also their invertase activity. We collected grape berries from Alphonse, Kmali Yapmcak, Cavus Efes Karasi, Cinsaut, Atasansi and Isabella grape varieties cultivated in Bozcaada island and Gelibolu peninsula. Twenty-one yeast species belonging to seven genera were identified. The yeast strains having high invertase activities were identified with 5.8S-ITS rDNA sequencing technique. The diversity of yeast biota on berries collected from Gelibolu was greater than that of Bozcaada. Metschnilcowia pulcherrima, Cryptococcus laurentii and Rhodotorula glutinis yeast species were dominant yeast species on grape berries. A total of 294 sucrose grown yeast strains showed growth on sucrose, and 19 of them exhibit the highest invertase activity that is not glucose repressible. These 19 yeast strains were identified as Starmerella bacillaris using 5.8S ITS rDNA region and the phylogenetic analysis was inferred with the Maximum Parsimony method.
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    Phylogenetic Analysis and Extracellular Enzyme Profiles of Yeast Strains Isolated from Raspberry Fruits
    (Çanakkale Onsekiz Mart Üniversitesi, 2021) Genc, Tulay Turgut; Günay, Melih
    Raspberry fruit contains phenolic compounds, flavones, flavonoids, vitamins, and antioxidant substances that are important properties for health and pharmacological sciences. Edible berries provide also a suitable habitat for the growth of various microorganisms. In this study, yeast biota associated with raspberry fruits was determined by molecular identification techniques. Raspberry fruits were collected from Çanakkale, Gelibolu (Gallipoli). Yeast strains were isolated and then identified by using the analysis of ITS1-5.8S-ITS2 rDNA gene sequences. The phylo-genetic analysis of all yeast strains was carried out by using the MEGA–X phylogenetic analysis tool. The extracel-lular enzyme profiles of identified yeast species were determined by the API-ZYM kit system. The distribution of yeast species on the raspberry fruits was determined as Hanseniaspora uvarum, Metschnikowia viticola, Aureo-basidium pullulans, and Metschnikowia pulcherrima. It was observed that yeast strains belong to Metschnikowia genus were dominant on raspberry fruits. All yeast strains in Metschnikowia genus showed different enzyme pro-files against seven extracellular enzymes. These enzymes may be the discriminatory enzymes for the yeast strains in the Metschnikowia genus. When the phylogenetic relationships among all yeast strains were investigated, all strains were divided into two main clades. While the first clade consists of only Metschnikowia genus, second clade includes H. uvarum and A. pullulans yeast species. Our results indicated that restriction patterns and also extracel-lular enzyme profiles could be utilized for differentiation of yeast strains within the genus. M. pulcherrima, H. uvarum, and A. pullulans can be used for industrial applications for future researches.
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    Reserve Carbohydrate Metabolism in Crabtree-Negative and - Positive Yeasts at Different Carbon Sources
    (Centre Excellence Molecular Biology-Cemb, 2020) Genc, Tulay Turgut
    Background: The fermentation of sugars into ethanol even in the presence of oxygen is referred to as the Crabtree effect. The yeast cells displaying Crabtree effect are indicated as Crabtree-positive yeast. Saccharomyces cerevisiae is Crabtree positive and Debatyomyces occidentalis is Crabtree-negative yeast which does not have Crabtree effect. The reserve carbohydrate metabolism is different in Crabtree-positive and Crabtree-negative yeast cells. The present study aimed to determine the trehalose and glycogen accumulation patterns both in Crabtree-positive and Crabtree-negative yeast species. Methods: In this research, trehalose and glycogen contents of S. cerevisiae and D. occidentalis yeast species were examined in a time course manner in three different carbon sources: glucose, galactose and glycerol. Firstly, yeast cells were grown in rich media supplemented with glucose then all washed and switched to fresh cultures including glucose, galactose and glycerol. Results: In S. cerevisiae yeast cells the overnight accumulated trehalose degraded very rapidly after nonfermentable carbon source replenishment, but this took place in a long time, nearly two days, in D. occidentalis yeast cells. However, whenever D. occidentalis yeast cells shifted to glycerol, all the accumulated trehalose degraded within the twelve hours. Glycogen accumulation in D. occidentalis yeast cells is lower than S. cerevisiae yeast cells both in fermentable and non-fermentable carbon sources. Conclusion: Results indicated that glycogen and trehalose accumulation patterns are completely different in D. occidentalis than S. cerevisiae. Crabtree-negative yeast cells generally, prefer to accumulate glycogen instead of trehalose as reserve carbohydrate. But in our research we proved that Crabtree-negative yeast D. occidentalis, accumulates more trehalose than S. cerevisiae yeast cells in non-fermentable carbon sources.