Use of a herbicide or lysine plus threonine for non-antibiotic selection of transgenic chickpea

A desensitized aspartate kinase (AK) gene has been developed as a non-antibiotic selection marker for use in the production of transgenic chickpea ( Cicer arietinum L.). Transgenic shoots regenerated from embryo explants bombarded with the desensitized AK gene were selected on media containing two amino acids, lysine and threonine (LT). Approximately 15% of the putative transgenic shoots of vars. P-362 and P-1042 survived after 4 weeks of growth on MSB5 medium (MS mineral salts and B5 vitamins) containing 2 microM thidiazuron (TDZ) and 2 mM lysine and 2 m M threonine. These shoots were subsequently grown on MSB5 medium supplemented with 2 micro M TDZ and 5 mM lysine and 5 mM threonine, and nearly 1% continued to grow after 16 weeks of selection. A phosphinothricin (PPT) selection system for Agrobacterium-mediated chickpea transformation was also developed. Three varieties of chickpea, P-362, P-1042 and P-1043, were successfully used for Agrobacterium transformation. Following Agrobacterium infection, 3-8% of the regenerated shoots remained green and continued to grow on MSB5 medium supplemented with 2.5 mg l(-1 )PPT. Increasing the concentrations of PPT to 15 mg l(-1) reduced transgenic shoot production in P-362, P-1042 and P-1043 to 0.7%, 1.2% and 1.1%, respectively. Selected putatively transformed shoots of all three varieties were rooted and grown to maturity. Southern hybridization analysis revealed single as well as multiple integration of genes in selected transgenic lines. The level of AK activity detected in LT-selected plants was higher than that detected in the non-transformed control.

Establishment of synchronization in carrot cell suspension culture and studies on stage specific activation of glyoxalase I

The present report summarizes and compares the effects of three cell cycle inhibitors, viz. aphidicolin, hydroxyurea and mimosine, in inducing synchronization of a rapidly proliferating suspension culture of carrot. These treatments efficiently synchronized the cell cycle as the doubling time of the cell population was roughly equal to the total length of one cell cycle. Protoplasts derived from mimosine treated cell suspension culture were resolved via flow cytometry to get an idea of the temporal organization of the cell cycle events. The biochemical analysis showed a rise in stage specific activity of glyoxalase I, an auxin inducible marker enzyme activated at G2-M. This activity peak could be shifted to an early phase of interphase in response to auxin treatment.

Transformation of haploid Datura innoxia protoplasts and analysis of the plasmid integration pattern in regenerated transgenic plants

We developed a highly efficient transformation protocol for the PEG-mediated direct transfer of plasmid DNA into protoplasts of haploid Datura innoxia. Vectors harbouring a neomycin phosphotransferase II gene or a hygromycin B phosphotransferase gene under the control of different promoters were used in the transformation experiments. Various amounts of plasmid DNA were applied without any carrier DNA to show the direct influence of the plasmid DNA concentration on the transformation efficiency. Approximately 95% of the selected calli were regenerated to plants; 20% of them remained haploid. Total DNA of different transgenic plants was analysed with regard to the integration pattern of the plasmid DNA. Plants carrying only one or two copies of the vector DNA were observed as well as individuals with multi-copy integration (up to ten or more copies).

Isolation and characterisation of satellite DNA from Brassica juncea (L.) Czern

Nuclear DNA isolated from hypocotyls (H), proliferating callus (PC) and differentiating callus (DC) of Brassica juncea contains a satellite DNA which can be resolved in actinomycin-D/CsCl gradients. The satellite DNA undergoes changes, when an in vitro culture is raised from hypocotyl tissue and forms a higher percentage of the genome in PC and DC than in mature differentiated tissue (hypocotyl). All the three satellite DNAs are GC-rich compared to main band DNAs. Satellite DNA of H has higher Tm and GC content than that of the PC and DC satellites. A 200 bp basic repeat unit from hypocotyl nuclear DNA has been cloned and characterised.

Regulation of cell proliferation and morphogenesis by amino acids inBrassica tissue cultures and its correlation with threonine deaminase

The effect of amino acids has been investigated with respect to the capacity ofBrassica cultures to undergo proliferation and differentiation. Hormone medium without any amino acid resulted in 6% shoot formation. Addition of optimal concentrations of L-leucine and L-isoleucine enhanced shoot formation upto 30% and 60%, respectively. L-methionine, L-threonine and pyruvic acid supported only proliferation but no differentiation. Amino acids had a marked effect on the activity of enzyme threonine deaminase (TD), bothin vivo andin vitro. TD in proliferating callus cultures was 3-fold higher than in differentiating cultures. Amino acids which induced cell proliferation increased TD while those which supported differentiation repressed it. Amino acids which did not alter TD activity had no effect on morphogenesis. The results suggest that amino acids play a regulatory role inBrassica morphogenesis which can be correlated with the activity of threonine deaminase.

Transformation and regeneration of Brassica oleracea mediated by an oncogenic Agrobacterium tumefaciens

A chimaeric neomycin phosphotransferase II (NPT II) gene was introduced in Brassica oleracea using an oncogenic strain of Agrobacterium tumefaciens harbouring Ti plasmid which contains Nos/NPTII in its T-DNA. The transformation of B. oleracea with the oncogenic Ti plasmid, resulted in regeneration of shoots and roots without any exogenous requirement of phytohormones. The presence of NPT II gene was determined by hybridization of Tn5 encoded NPT II gene with DNA of kanamycin resistant regenerated plants. The expression of NPT II was demonstrated by kanamycin phosphorylation assay. Several regenerated plants were obtained, a few of them were found to be morphological variants and a chlorophyll deficient mutant plant was also obtained.

Induction and differentiation of callus from embryos of Cocos nucifera L. by IAA-conjugates

Calli from young embryos of Cocos nucifera L. were induced on B5 medium supplemented with IAA-conjugates (IAA-asp or IAA-ala) at a concentration of 2.0 mg/1 and callusing was increased by about 10% if both IAA-conjugates, IAA-asp and IAA-ala were added together. Differentiation of shoots and roots was achieved by transferring calli to B5 medium supplemented with either IAA-asp (2.0 mg/1)+Kn(2.0 mg/1) or NAA (2.0 mg/1). Complete plantlets were obtained on B5 medium supplemented with NAA (0.5 mg/1)+BAP (2.0 mg/1)+PVP (1.0 g/1).

Correlation of glyoxalase I activity with cell proliferation inDatura callus culture

Glyoxalase-I activity in growingDatura callus showed 184% increase with the age of the culture. Spermidine increased the enzyme activity together with DNA and protein synthesis. With the addition of mitotic inhibitors, vinblastine and methylglyoxal in the growth medium, the enzyme activity was inhibited by 92 percent and 50 percent respectively, at the most effective concentration and the callus growth was also reduced. Similar results were obtained with specific glyoxalase I inhibitors, iso-ascorbate and squaric acid.