Synthesis of carbon nanotubes by swirled floating catalyst chemical vapour deposition method.

A series of developments have been made in synthesizing Carbon Nanotubes (CNTs) by Catalytic Vapour Deposition (CVD) methods since its discovery as a possible route to the large scale and high quality production of CNTs. In this study, CNTs were synthesized continuously in a swirled floating catalytic chemical vapour deposition reactor using acetylene as carbon source, ferrocene as catalyst, with argon and hydrogen as carrier gases within the temperature range of 900-1050 degrees C. The effects of pyrolysis temperature, acetylene flow rate, hydrogen flow rate, and ratio of flow of acetylene to hydrogen on the rate of production of CNTs were investigated. The CNTs produced were purified with dilute nitric acid and the nature and quality of the CNTs were analysed by TEM, Raman spectrometer, EDX, and TGA. Results obtained revealed that a mixture of single and multi wall carbon nanotubes were produced continuously with a maximum yield rate of 0.31 g/min at 1000 degrees C and a flow ratio of acetylene to hydrogen of one to five.

Transgene behaviour in populations of rice plants transformed using a new dual binary vector system: pGreen/pSoup.

Transgene integration, expression level and stability have been studied, across two generations, in a population of rice plants transformed using a new dual binary vector system: pGreen/pSoup. pGreen is a small Ti binary vector unable to replicate in Agrobacterium without the presence of another binary plasmid, pSoup, in the same strain. We engineered both pGreen and pSoup to contain each a different T-DNA. Transformation experiments were conducted using a pGreen vector containing the bar and gusA expression units (no transgene in pSoup) or with a pSoup vector containing an aphIV and gfp expression units (no transgene in pGreen). High plant transformation frequencies (up to 40%) were obtained using herbicide resistance ( bar) or antibiotic resistance ( aphIV) genes. Around 80% of the independently transformed plants expressed unselected reporter genes ( gusA or gfp) present in the vectors. Backbone sequences transfer was frequent (45% of lines) and occurred often in multicopy lines. Around 15-20% of the rice plant lines contained a single T-DNA integration without backbone. Integration of additional transgene copies did not improve expression levels in either T(0) plants or T(1) progenies. Nearly all multicopy lines contained transgenes integrated at several loci in the plant genome, showing that T-DNAs from either pGreen or pSoup frequently integrated at unlinked loci. Precise determination of loci number required the analysis of transgene presence in progeny. Segregation of transgene phenotype was generally misleading and tended to underestimate the real number of transgenic loci. The contribution of this new dual-binary vector system to the development of high-throughput rice transformation systems and to the production of marker-free transgenic rice plants is discussed.

A large-scale study of rice plants transformed with different T-DNAs provides new insights into locus composition and T-DNA linkage configurations.

Transgenic locus composition and T-DNA linkage configuration were assessed in a population of rice plants transformed using the dual-binary vector system pGreen (T-DNA containing the bar and gus genes)/pSoup (T-DNA containing the aphIV and gfp genes). Transgene structure, expression and inheritance were analysed in 62 independently transformed plant lines and in around 4,000 progeny plants. The plant lines exhibited a wide variety of transgenic locus number and composition. The most frequent form of integration was where both T-DNAs integrated at the same locus (56% of loci). When single-type T-DNA integration occurred (44% of loci), pGreen T-DNA was preferentially integrated. In around half of the plant lines (52%), the T-DNAs integrated at two independent loci or more. In these plants, both mixed and single-type T-DNA integration often occurred concurrently at different loci during the transformation process. Non-intact T-DNAs were present in 70-78% of the plant lines causing 14-21% of the loci to contain only the mid to right border part of a T-DNA. In 53-66% of the loci, T-DNA integrated with vector backbone sequences. Comparison of transgene presence and expression in progeny plants showed that segregation of the transgene phenotype was not a reliable indicator of either transgene inheritance or T-DNA linkage, as only 60-80% of the transgenic loci were detected by the expression study. Co-expression (28% of lines) and backbone transfer (53-66% of loci) were generally a greater limitation to the production of marker-free T(1) plants expressing the gene of interest than co-transformation (71% of lines) and unlinked integration (44% of loci).