Evidence that exogenous urea acts as a potent cue to alleviate ammonium-inhibition of root system growth of cotton plant (Gossypium hirsutum).

Many plants grown with low-millimolar concentration of NH4 + as a sole nitrogen source develop NH4 + -toxicity symptoms. To date, crucial molecular identities and a practical approach involved in the improvement of plant NH4 + -tolerance remain largely unknown. By phenotyping of upland cotton grown on varied nitrogen forms, we came across a phenomenon that caused sub-millimolar concentrations of urea (e.g., up 50 µM) to repress the growth inhibition of roots and whole plant cultivated in a NH4 + -containing nutrient solution. A growth-recovery assay revealed that the relief in NH4 + -inhibited growth required only a short-term exposure (≧12 h) of the roots to urea, implying that urea could elicit an internal signaling and be involved in antagonizing NH4 + -sensitivity. Intriguingly, split-root experiments demonstrated that low urea occurrence in one root-half could efficaciously stimulate not only supplied root but also the root-half grown in NH4 + -solution without urea, indicating the existence of urea-triggered local and systemic long-distance signaling. In the split-root experiment we also observed high arginase activity, strong arginine reduction and remarkable upregulation of polyamine biosynthesis-related genes (ADC1/2, SPDS and SPMS). Therefore, we suggest that external urea might serve as an effective cue (signal molecule) in an arginine-/polyamine-related process for ameliorating NH4 + -suppressed root growth, providing a novel aspect for deeper exploring and understanding plant NH4 + -tolerance.

Effects of exogenous p53 transfection on the gene expression in the human brain glioma cell line U251.

The p53 gene is activated in response to several malignancy-associated stress signals by transactivation of downstream genes and by transcription-independent mechanisms. In order to identify new p53 downstream genes, we established a new system of p53 gene inducible expression, U251-pTet-p53 cell line, with the Tet-On Gene Expression System, in which exogenous p53 gene could overexpress in doxycycline (Dox) medium but not in the medium without Dox. By comparing their random primer RT-PCR products, it was proved that exogenous p53 gene expression could lead to many genes differential expression, some up-expressed and others down-expressed. All of these differential expressed genes may be p53 downstream genes. We can gain the magnitude of p53 downstream genes, which provides the basis of directly cloning of novel p53 downstream genes and further studying of p53 regulatory network.

Characterization of the human PAP1 gene and its homologue possible involvement in mouse embryonic development.

We have identified PAP1 gene, a novel member of the immunoglobulin superfamily (IGSF) from U251-pTet-p53 cell line, which carried a wild-type p53 transgene. The gene has been localised to chromosome 16p12-13. Alignment of the predicted protein sequence for Human, Pan troglodytes, Canis, Mus musculus and Gallus gallus revealed it was highly conserved. Its homologue, IGSF6, possible involves in mouse embryonic development. The presence of IGSF6 specific transcript was detected by Northern blot in the RNAs extracted from 11 to 14 day postconception. IGSF6 expression is different in mouse embryos of the different ages. In situ hybridization performed on mice embryos sections showed the differential presence of IGSF6 in developing lung and kidney. This structure and differential expression suggests a function involvement in embryonic development, perhaps involvement in cell proliferation.

[Effect of polysaccharides content of tissue culturing seedlings on Dendrobium candidium under sound wave stimulation].

OBJECTIVE: To detect the polysaccharides content of tissue culturing seedlings on Dendrobium candidium under special sound wave stimulation. METHODS: The content of polysaccharides was detected by phenol-vitriol colorimetry method. RESULTS: The polysaccharides content of the groups stimulated continuously for 24d was higher obviously than the content of the control groups. CONCLUSION: The stimulation of the special sound wave promoted markedly the synthesis of polysaccharides in D. candidium. It may affect obviously the metabolic pathway of polysaccharides in D. candidium.

[A comparative study on isoenzymes of Sarcocystis spp. from cattle and water buffaloes].

OBJECTIVE: To analyze the zymogram of peroxidase (PER) and phosphoglucose isomerase (PGI) of three species of Sarcocystis. METHODS: The collected parasites were homogenized and fragmented by ultrasonication. After centrifugation, the supernatants were analyzed by isoelectric focusing electrophoresis. RESULTS: The isolates of S. cruzi from infected water buffalo and cattle all showed identical enzyme profiles, 7 bands of PER at pH 4.44-6.98 and 6 bands of PGI at pH 4.66-6.53; and same with the isolates of S. hirsuta. 5 bands of PER at pH 4.97-7.15 and 4 bands of PGI at pH 4.70-6.51. The zymograms among S. cruzi, S. hirsuta and S. fusiformis were different considerably. CONCLUSION: The data support the hypothesis that both water buffalo and cattle are the natural intermediate hosts of S. cruzi and S. hirsuta at the gene level. S. cruzi, S. hirsuta and S. fusiformis are different species.