Plastids of nongreen tissues import carbon as a source of biosynthetic pathways and energy. Within plastids, carbon can be used in the biosynthesis of starch or as a substrate for the oxidative pentose phosphate pathway, for example. We have used maize endosperm to purify a plastidic glucose 6-phosphate/phosphate translocator (GPT). The corresponding cDNA was isolated from maize endosperm as well as from tissues of pea roots and potato tubers. Analysis of the primary sequences of the cDNAs revealed that the GPT proteins have a high degree of identity with each other but share only ‫ف‬ 38% identical amino acids with members of both the triose phosphate/phosphate translocator (TPT) and the phosphoenolpyruvate/phosphate translocator (PPT) families. Thus, the GPTs represent a third group of plastidic phosphate antiporters. All three classes of phosphate translocator genes show differential patterns of expression. Whereas the TPT gene is predominantly present in tissues that perform photosynthetic carbon metabolism and the PPT gene appears to be ubiquitously expressed, the expression of the GPT gene is mainly restricted to heterotrophic tissues. Expression of the coding region of the GPT in transformed yeast cells and subsequent transport experiments with the purified protein demonstrated that the GPT protein mediates a 1:1 exchange of glucose 6-phosphate mainly with inorganic phosphate and triose phosphates. Glucose 6-phosphate imported via the GPT can thus be used either for starch biosynthesis, during which process inorganic phosphate is released, or as a substrate for the oxidative pentose phosphate pathway, yielding triose phosphates. INTRODUCTIONDuring C 3 photosynthesis, energy from solar radiation is used for the formation of phosphorylated C3 sugar phosphates, triose phosphates (trioseP), and 3-phosphoglycerate (3-PGA); these products are exported from the chloroplasts into the cytosol via the trioseP/3-PGA/phosphate translocator (TPT). In the mature leaves of most plants, the exported photosynthates are then used in the formation of sucrose, which is allocated via the phloem to the heterotrophic plant organs, such as young leaves, roots, seeds, fruits, or tubers. In these sink tissues, sucrose serves as a source of carbon and energy and is first cleaved by the action of invertases or sucrose synthase; the products of these reactions are converted into hexose phosphates.Nongreen plastids of heterotrophic tissues are carbohydrate-importing organelles and, in the case of amyloplasts of storage tissues, the site of starch synthesis. Because these plastids are normally not able to generate hexose phosphates from C3 compounds due to the absence of fructose 1,6-bisphosphatase activity (Entwistle and ap Rees, 1988), they rely on the import of cytosolically generated hexose phosphates as the source of carbon for starch biosynthesis and, in addition, for the oxidative pentose phosphate pathway. The results of transport measurements with intact organelles or reconstituted tissues from different plants suggest that thi...

Plastids of nongreen tissues import carbon as a source of biosynthetic pathways and energy. Within plastids, carbon can be used in the biosynthesis of starch or as a substrate for the oxidative pentose phosphate pathway, for example. We have used maize endosperm to purify a plastidic glucose 6-phosphate/phosphate translocator (GPT). The corresponding cDNA was isolated from maize endosperm as well as from tissues of pea roots and potato tubers. Analysis of the primary sequences of the cDNAs revealed that the GPT proteins have a high degree of identity with each other but share only approximately 38% identical amino acids with members of both the triose phosphate/phosphate translocator (TPT) and the phosphoenolpyruvate/phosphate translocator (PPT) families. Thus, the GPTs represent a third group of plastidic phosphate antiporters. All three classes of phosphate translocator genes show differential patterns of expression. Whereas the TPT gene is predominantly present in tissues that perform photosynthetic carbon metabolism and the PPT gene appears to be ubiquitously expressed, the expression of the GPT gene is mainly restricted to heterotrophic tissues. Expression of the coding region of the GPT in transformed yeast cells and subsequent transport experiments with the purified protein demonstrated that the GPT protein mediates a 1:1 exchange of glucose 6-phosphate mainly with inorganic phosphate and triose phosphates. Glucose 6-phosphate imported via the GPT can thus be used either for starch biosynthesis, during which process inorganic phosphate is released, or as a substrate for the oxidative pentose phosphate pathway, yielding triose phosphates.

Background: Candida albicans resides on epithelial surfaces as part of the physiological microflora. However, under certain conditions it may cause life-threatening infections like Candida sepsis. Human β-defensins (hBDs) are critical components of host defense at mucosal surfaces and we have recently shown that hBD-2 and hBD-3 are upregulated in Candida esophagitis. We therefore studied the role of Candidate signalling pathways in order to understand the mechanisms involved in regulation of hBD-expression by C. albicans. We used the esophageal cell line OE21 and analysed the role of paracrine signals from polymorphonuclear leukocytes (PMN) in an in vitro model of esophageal candidiasis.

The bactericidal activity of the novel beta-defensin hBD-3 against 28 species and 55 strains of gram-positive cocci and gram-negative fermentative and nonfermentative rods was tested. All strains proved to be highly or intermediately susceptible to hBD-3 (minimal bactericidal concentration [MBC], <50 g/ml), except for Burkholderia cepacia, for all 23 tested strains of which MBCs were >100 g/ml.

SummaryThe inducible crassulacean acid metabolism (CAM) plant Mesembryanthemum crystallinum accumulates malic acid during the night and converts it to starch during the day via a pathway that, because it is located in different subcellular compartments, depends on speci®c metabolite transport across membranes. The chloroplast glucose transporter (pGlcT) and three members of the phosphate translocator (PT) family were isolated. After induction of CAM, transcript amounts of the phosphoenolpyruvate (PEP) phosphate translocator (PPT) and the glucose-6-phosphate (Glc6P) phosphate translocator (GPT) genes were increased drastically, while triose phosphate (TP) phosphate translocator (TPT) and the pGlcT transcripts remained unchanged. PPT-and GPT-speci®c transcripts and transporter activities exhibited a pronounced diurnal variation, displaying the highest amplitude in the light. pGlcT transcripts were elevated towards the end of the light period and at the beginning of the dark period. These ®ndings, combined with diurnal variations of enzyme activities and metabolite contents, helped to elucidate the roles of the PPT, GPT, TPT and pGlcT in CAM. The main function of the PPT is the daytime export from the stroma of PEP generated by pyruvate orthophosphate:dikinase (PPDK). The increased transport activity of GPT in the light suggests a higher requirement for Glc6P import for starch synthesis rather than starch mobilization. Most likely, Glc6P rather than 3-phosphoglycerate or triose phosphates is the main substrate for daytime starch biosynthesis in M. crystallinum plants in which CAM has been induced (CAM-induced), similar to non-green plastids. In the dark, starch is mobilized both phosphorylytically and amylolytically and the products are exported by the GPT, TPT and pGlcT. The transport activities of all three phosphate translocators and the transcript amounts of the pGlcT adapt to changing transport requirements in order to maintain high metabolic uxes during the diurnal CAM cycle.

Searching the database for mouse homologs of the antimicrobial peptide human beta-defensin-3 (hBD-3) revealed highest identity (69%) to mouse beta-defensin-14 (mBD-14). Recombinant mBD-14 exhibited broad-spectrum, nanomolar microbicidal activity. Treatment of keratinocytes with gamma interferon or transforming growth factor alpha increased mBD-14 gene expression. These data suggest that mBD-14 is the functional ortholog of hBD-3.

Antimicrobial resistance in genital mycoplasmas is increasing and shows global variation. We determined the susceptibilities of 469 mycoplamas, comprising 290 Mycoplasma hominis and 179 ureaplasma isolates collected during 1983 and 1989-2004, to eleven antibacterials by agar dilution. Additionally, we analyzed the results of routine E-testing during 2005-2008. Doxycycline was the most active tetracycline with (MIC₉₀ of 1 and 8 mg/L for ureaplasmas and M. hominis, respectively. Significantly more M. hominis isolates (approximately 10-13%) than ureaplasmas (approximately 1-3%) were resistant to tetracyclines. Ofloxacin was effective against both species (>95% susceptibility). Ciprofloxacin was moderately active against M. hominis and less active against ureaplasmas (70.3% and 35.2% susceptibility, respectively). Clarithromycin and josamycin were the most potent macrolides (MIC₉₀ of 0.5 mg/L) against ureaplasmas. Erythromycin had the lowest activity (MIC₉₀ of 8 mg/L) against ureaplasmas like clindamycin which was the most potent agent against M. hominis. Cross-resistance was found between tetracyclines (53-93%), macrolides and erythromycin (70-100%), and between erythromycin and ciprofloxacin (43-55%). M. hominis became more resistant to tetracyclines and fluoroquinolones between 1989 and 2004, although there was little change during 2005-2008. Ureaplasmas became more resistant to cipfloxacin during 1997 – 2004 and showed high resistance rates to erythromycin during 1989-2008. Doxycycline is still the drug of first-choice for the treatment of ureaplasmal infections and may be used for co-infection with M. hominis.

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