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1.
Heat stress reduces maize yield and several lines of evidence suggest that the heat lability of maize endosperm ADP-glucose pyrophosphorylase (AGPase) contributes to this yield loss. AGPase catalyzes a rate-limiting step in starch synthesis. Herein, we present a novel maize endosperm AGPase small subunit variant, termed BT2-TI that harbors a single amino acid change of residue 462 from threonine to isoleucine. The mutant was isolated by random mutagenesis and heterologous expression in a bacterial system. BT2-TI exhibits enhanced heat stability compared to wildtype maize endosperm AGPase.The TI mutation was placed into another heat-stable small subunit variant, MP. MP is composed of sequences from the maize endosperm and the potato tuber small subunit. The MP-TI small subunit variant exhibited greater heat stability than did MP. Characterization of heat stability as well as kinetic and allosteric properties suggests that MP-TI may lead to increased starch yield when expressed in monocot endosperms. 相似文献
2.
Lyndsey R. Buckner Angela M. Amedee Hannah L. Albritton Pamela A. Kozlowski Nedra Lacour Chris L. McGowin Danny J. Schust Alison J. Quayle 《PloS one》2016,11(1)
Chlamydia trachomatis causes a predominantly asymptomatic, but generally inflammatory, genital infection that is associated with an increased risk for HIV acquisition. Endocervical epithelial cells provide the major niche for this obligate intracellular bacterium in women, and the endocervix is also a tissue in which HIV transmission can occur. The mechanism by which CT infection enhances HIV susceptibility at this site, however, is not well understood. Utilizing the A2EN immortalized endocervical epithelial cell line grown on cell culture inserts, we evaluated the direct role that CT-infected epithelial cells play in facilitating HIV transmission events. We determined that CT infection significantly enhanced the apical-to-basolateral migration of cell-associated, but not cell-free, HIVBaL, a CCR5-tropic strain of virus, across the endocervical epithelial barrier. We also established that basolateral supernatants from CT-infected A2EN cells significantly enhanced HIV replication in peripheral mononuclear cells and a CCR5+ T cell line. These results suggest that CT infection of endocervical epithelial cells could facilitate both HIV crossing the mucosal barrier and subsequent infection or replication in underlying target cells. Our studies provide a mechanism by which this common STI could potentially promote the establishment of founder virus populations and the maintenance of local HIV reservoirs in the endocervix. Development of an HIV/STI co-infection model also provides a tool to further explore the role of other sexually transmitted infections in enhancing HIV acquisition. 相似文献
3.
Bhuwan Joshi Ayan Chakrabarty Christopher Bruot Hannah Ainsworth Gail Fraizer et al. 《Plant Growth Regulation》1989,8(3):286-286
Book Review
Techniques in molecular biologyJ.M. Walker and W. Gaastra (Eds.), vol. 2. London: Croom Helm, 1987. iv + 332 pages. £14.95. ISBN 0-7099-3673-7 相似文献4.
5.
Characterization of the DNA-binding properties of the receptor for 2,3,7,8-tetrachlorodibenzo-p-dioxin 总被引:1,自引:0,他引:1
R R Hannah J Lund L Poellinger M Gillner J A Gustafsson 《European journal of biochemistry》1986,156(2):237-242
The DNA-binding properties of the receptor for 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) were investigated using chromatography on DNA-cellulose columns. A maximal binding of about 40% of the total receptor complex to DNA-cellulose was observed. In order to interact with DNA, the receptor must first bind TCDD. A heat-activation step followed by gel permeation chromatography using Sephadex G-25 increased the binding of the cytosolic receptor to DNA. The DNA-binding ability of the receptor was almost lost following mild proteolysis using trypsin or alpha-chymotrypsin, although these treatments did not reduce its ligand binding capacity and had no apparent effect on its size. Furthermore, pre-treatment of the DNA-cellulose column with an intercalating drug, ethidium bromide, resulted in inhibition of the binding of the TCDD-receptor complex to DNA, indicating that not only electrostatic interactions but also the configuration of DNA are of importance in receptor-DNA interactions. 相似文献
6.
To characterize the movement of sugars during kernel development in maize, a newly devised in vitro kernel development scheme was utilized. Viable seeds of wild type maize (Zea mays L.) as well as the mutant shrunken-2 (sh2) were found to mature when grown in culture with reducing sugars or sucrose as the carbon source. However, wild type and sh2 kernels had greater germination, starch content, and seed weight when sucrose, rather than reducing sugars, was the carbon source. By the use of labeled sucrose it was shown that sucrose can move into endosperm tissue without intervening degradation and resynthesis. These results show that when grown in vitro the maize seed can utilize reducing sugars for development, but it prefers sucrose. 相似文献
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Eukaryotic cells normally replicate their DNA only once between mitoses. Unlike G1 nuclei, intact G2 nuclei do not replicate during incubation inXenopusegg extract. However, artificial permeabilization of the nuclear membrane of G2 nuclei allows induction of new initiations byXenopusegg extract. This is consistent with the action of a replication licensing factor which is believed to enter the nucleus when the nuclear membrane breaks down at mitosis. Here, we show that G2 nuclei will initiate a new round of replication in the absence of nuclear membrane permeabilization, if they are preexposed to protein kinase inhibitorsin vivo.Competence to rereplicate is generated within 30 min of drug treatment, well before the scheduled onset of mitosis. This demonstrates that a protein kinase-dependent mechanism is continually active in G2 phase to actively prevent regeneration of replication capacity in mammalian cells. Kinase inhibition in G2 cells causes nuclear accumulation of replication protein A. Rereplication of kinase-inhibited G2 nuclei also depends on factors supplied byXenopusegg extract, which are distinct from those required for replication licensing. 相似文献
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