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    Abiotic stress tolerance and growth responses of transgenic potato (Solanum tuberosum L. cv. Kennebec) plants expressing rice Osmyb4 gene
    (ELSEVIER SCIENCE BV, 2012) Aydin, Gulsum; Yucel, Meral; Oktem, Huseyin Avni
    [Abstract not Available]
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    Cold-induced comparative transcriptome analysis of Potato (Solanum tuberosum L. cv. Kennebec) that heterologously expresses the rice Osmyb4 gene
    (ELSEVIER SCIENCE BV, 2016) Aydin, Gulsum; Oz, Mehmet Tufan; Yucel, Meral; Oktem, Huseyin Avni
    [Abstract not Available]
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    Effect of Light Intensity, Wavelength and Illumination Protocol on Hydrogen Production in Photobioreactors
    (Bentham Science Publ, 2012) Uyar, Basar; Yucel, Meral; Gunduz, Ufuk; Eroglu, Inci
    Photofermentative hydrogen production is a bioprocess in which photosynthetic purple nonsulfur bacteria grow heterotrophically on organic acids like acetic acid, lactic acid and butyric acid and produce hydrogen using light energy under anaerobic conditions. Two enzymes are specifically involved in hydrogen production, namely nitrogenase and hydrogenase. While nitrogenases produce hydrogen under nitrogen-limited conditions acting as ATP-dependent hydrogenase, hydrogenases have the ability for both production and consumption of molecular hydrogen depending on the type of hydrogenase and physiological conditions. Photofermentation process can be achieved in a wide variety of conditions such as in batch or continuous mode, upon artificial or solar illumination, utilizing various carbon and nitrogen sources including food industry wastewater and dark fermentation effluents. Panel and tubular photobioreactors are the most applicable bioreactor types since they ensure simple design, reasonable material and production costs and high light energy utilization. Physiological parameters such as pH, temperature, medium composition and light intensity control the yield and hydrogen productivity of the bacteria. Hydrogen productivity and yield can also be increased by using genetically modified bacterial strains or immobilization of bacteria. Genetic studies focus on development of mutant strains by disrupting the uptake hydrogenase genes, altering pigmentation and blocking alternative by-product biosynthesis. Techno-economic evaluations show that photofermentative hydrogen production process is very near to the commercialization stage, however demo scale experience is necessary to solve some problems such as low rate of hydrogen production and the cost associated with photobioreactor scale-up. Furthermore, recent studies are trying to integrate photofermentation to dark fermentation to have an enhanced hydrogen production yield. Finally, the whole process could end up with a fuel cell application where the produced hydrogen is stored for future uses.
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    Evaluation of abiotic stress tolerance and physiological characteristics of potato (Solanum tuberosum L. cv. Kennebec) that heterologously expresses the rice Osmyb4 gene
    (SPRINGER, 2014) Aydin, Gulsum; Yucel, Meral; Chan, Ming-Tsair; Oktem, Huseyin Avni
    MYB transcription factors are involved in diverse biochemical and physiological processes, including hormone signaling, defense, and stress responses. In the present study, we developed a transgenic potato (Solanum tuberosum L. cv. Kennebec) expressing the rice Osmyb4 gene, which encodes the transcription factor MYB4. The transgene was under the control of either the constitutive CaMV35S promoter or the stress-induced Arabidopsis COR15a promoter. The potential involvement of MYB4 in certain physiological processes and the abiotic stress response in the potato was evaluated. The transgenic plants did not exhibit growth retardation, and they showed no significant difference (P < 0.05) in tuber yield from that of non-transgenic wild-type plants. Although the chlorophyll a and b as well as the anthocyanin contents of the six transgenic lines were similar to those of the wild type, the transgenic line S2 presented a significantly higher carotenoid content. The total sugar contents of the lines S2 and M48 were significantly higher than that of the wild-type plants. S2 and M48 were significantly more tolerant of salinity than the wild type, according to measured growth parameters. Transgenic plants grown under a high concentration of boric acid (3 mM) exhibited greater survival rates than non-transgenic control plants. On the other hand, the transgenic plants did not show an improvement in freezing tolerance. Overall, our results indicated that MYB4 may affect diverse processes such as carotenoid biosynthesis, sugar metabolism, and salinity tolerance in potato, and that it may be an upstream regulatory element of these processes.
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    Evaluation of hydrogen production by Rhodobacter sphaeroides OU001 and its hupSL deficient mutant using acetate and malate as carbon sources
    (PERGAMON-ELSEVIER SCIENCE LTD, 2009) Kars, Goekhan; Gunduz, Ufuk; Yucel, Meral; Rakhely, Gabor; Kovacs, Kornel L.; Eroglu, Inci
    Rhodobacter sphaeroides O.U.001 is one of the candidates for photobiological hydrogen production among purple non-sulfur bacteria. Hydrogen is produced by Mo-nitrogenase from organic acids such as malate or lactate. A hupSL in frame deletion mutant strain was constructed without using any antibiotic resistance gene. The hydrogen production potential of the R. sphaeroides O.U.001 and its newly constructed hupSL deleted mutant strain in acetate media was evaluated and compared with malate containing media. The hupSL(-) R. sphaeroides produced 2.42 l H-2/l culture and 0.25 l H-2/l culture in 15 mM malate and 30 mM acetate containing media, respectively, as compared to the wild type cells which evolved 1.97 l H-2/l culture and 0.21 l H-2/l culture in malate and acetate containing media, correspondingly. According to the results, hupSL- R. sphaeroides is a better hydrogen producer but acetate alone does not seem to be an efficient carbon source for photo-heterotrophic H-2 production by R. sphaeroides. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.