[Structure and species diversity of Cerasus community in Dawei Mountain of Hunan, China.] / å¤§å›´å±±æ¨±å±žæ¤ç‰©ç¾¤è½ç»“æž„åŠç‰©ç§å¤šæ ·æ€§.

To provide a scientific basis for the conservation and exploitation of wild Cerasus species in Dawei Mountain, we investigated the community characteristics and species diversity of Cerasus species. The results showed that there were four Cerasus communities, C. campanulata, C. diel-siana, C. conradinae and C. xueluoensis, in Dawei Mountain. Phaenerophyte in the life form and pantropical elements in the local flora were both dominant. The shrub layer had higher species diversity than that of the arbor layer. Species diversity of those four communities was following the order of C. dielsiana, C. conradinae, C. campanulata and C. xueluoensis. The community structure was relatively stable when young and mature individuals of Cerasus predominated. The ground dia-meter class structure indicated that the C. xueluoensis population was a growing population with a typical pyramid structure. The C. conradinae community was mono-dominated by C. conradinae, with C. dielsiana and C. campanulata as the important companion species. Those three Cerasus species would be replaced by other coniferous and broadleaved species due to the shortage of natural regeneration.

Construction of EGFP-labeling system for visualizing the infection process of Xanthomonas axonopodis pv. citri in planta.

Xanthomonas axonopodis pv. citri (Xac) is the causal agent of citrus bacterial canker, an economically important disease to world citrus industry. To monitor the infection process of Xac in different citrus plants, the enhanced green florescent protein (EGFP) visualizing system was constructed to visualize the propagation and localization in planta. First, the wild-type Xac was isolated from the diseased leaves of susceptible 'Bingtang' sweet orange, and then the isolated Xac was labeled with EGFP by triparental mating. After PCR identification, the growth kinetics and pathogenicity of the transformants were analyzed in comparison with the wild-type Xac. The EGFP-labeled bacteria were inoculated by spraying on the surface and infiltration in the mesophyll of 'Bingtang' sweet orange leaves. The bacterial cell multiplication and diffusion processes were observed directly under confocal laser scanning microscope at different intervals after inoculation. The results indicated that the EGFP-labeled Xac releasing clear green fluorescence light under fluorescent microscope showed the infection process and had the same pathogenicity as the wild type to citrus. Consequently, the labeled Xac demonstrated the ability as an efficient tool to monitor the pathogen infection.

A high-throughput dielectrophoresis-based cell electrofusion microfluidic device.

A high-throughput cell electrofusion microfluidic chip has been designed, fabricated on a silicon-on-insulator wafer and tested for in vitro cell fusion under a low applied voltage. The developed chip consists of six individual straight microchannels with a 40-µm thickness conductive highly doped Si layer as the microchannel wall. In each microchannel, there are 75 pairs of counter protruding microelectrodes, between which the cell electrofusion is performed. The entire highly doped Si layer is covered by a 2-µm thickness aluminum film to maintain a consistent electric field between different protruding microelectrode pairs. A 150-nm thickness SiO2 film is subsequently deposited on the top face of each protruding microelectrode for better biocompatibility. Owing to the short distance between two counter protruding microelectrodes, a high electric field can be generated for cell electrofusion with a low voltage imposed across the electrodes. Both mammalian cells and plant protoplasts were used to test the cell electrofusion. About 42-68% cells were aligned to form cell-cell pairs by the dielectrophoretic force. After cell alignment, cell pairs were fused to form hybrid cells under the control of cell electroporation and electrofusion signals. The averaged fusion efficiency in the paired cells is above 40% (the highest was about 60%), which is much higher than the traditional polyethylene glycol method (<5%) and traditional electrofusion methods (∼12%). An individual cell electrofusion process could be completed within 10 min, indicating a capability of high throughput.