https://www.cell.com/trends/plant-science/pdf/S1360-1385(02)02251-3.pdf

GATEWAY vectors for Agrobacterium-mediated plant transformation.

It is concluded from a review of the literature that plant cell culture itself generates genetic variability (somaclonal variation). Extensive examples are discussed of such variation in culture subclones and in regenerated plants (somaclones). A number of possible mechanisms for the origin of this phenomenon are considered. It is argued that this variation already is proving to be of significance for plant improvement. In particular the phenomenon may be employed to enhance the exchange required in sexual hybrids for the introgression of desirable alien genes into a crop species. It may also be used to generate variants of a commercial cultivar in high frequency without hybridizing to other genotypes.

Somaclonal variation — a novel source of variability from cell cultures for plant improvement

During the past decade the pesticidal bacterium Bacillus thuringiensis has been the subject of intensive research. These efforts have yielded considerable data about the complex relationships between the structure, mechanism of action, and genetics of the organism’s pesticidal crystal proteins, and a coherent picture of these relationships is beginning to emerge. Other studies have focused on the ecological role of the B. thuringiensis crystal proteins, their performance in agricultural and other natural settings, and the evolution of resistance mechanisms in target pests. Armed with this knowledge base and with the tools of modern biotechnology, researchers are now reporting promising results in engineering more-useful toxins and formulations, in creating transgenic plants that express pesticidal activity, and in constructing integrated management strategies to insure that these products are utilized with maximum efficiency and benefit.

Bacillus thuringiensis and Its Pesticidal Crystal Proteins

The complete nucleotide sequence (155 844 bp) of tobacco (Nicotiana tabacum var. Bright Yellow 4) chloroplast DNA has been determined. It contains two copies of an identical 25 339 bp inverted repeat, which are separated by a 86 684 bp and a 18 482 bp single-copy region. The genes for 4 different rRNAs, 30 different tRNAs, 39 different proteins and 11 other predicted protein coding genes have been located. Among them, 15 genes contain introns. Blot hybridization revealed that all rRNA and tRNA genes and 27 protein genes so far analysed are transcribed in the chloroplast and that primary transcripts of the split genes hitherto examined are spliced. Five sequences coding for proteins homologous to components of the respiratory-chain NADH dehydrogenase from human mitochondria have been found. The 30 tRNAs predicted from their genes are sufficient to read all codons if the ;two out of three' and ;U:N wobble' mechanisms operate in the chloroplast. Two sequences which autonomously replicate in yeast have also been mapped. The sequence and expression analyses indicate both prokaryotic and eukaryotic features of the chloroplast genes.

The complete nucleotide sequence of the tobacco chloroplast genome: its gene organization and expression.

Rice (Oryza sativa), a major staple food, is usually milled to remove the oil-rich aleurone layer that turns rancid upon storage, especially in tropical areas. The remaining edible part of rice grains, the endosperm, lacks several essential nutrients, such as provitamin A. Thus, predominant rice consumption promotes vitamin A deficiency, a serious public health problem in at least 26 countries, including highly populated areas of Asia, Africa, and Latin America. Recombinant DNA technology was used to improve its nutritional value in this respect. A combination of transgenes enabled biosynthesis of provitamin A in the endosperm.

https://science.sciencemag.org/content/sci/287/5451/303.full.pdf

Engineering the Provitamin A (β-Carotene) Biosynthetic Pathway into (Carotenoid-Free) Rice Endosperm

Selectable marker gene and methods of use thereof in transplastomic plants

Compositions and methods for manipulating the plastid genome of higher plants are provided.

Removal of plastid sequences by transiently expressed site-specific recombinases

Initial developments in the field of plant-based vaccines have been limited by low level of immunogen expression from nuclear genes. An alternative method is to express vaccine antigens from the chloroplast genome. Recently, we developed a production system for expression of recombinant proteins in tobacco chloroplasts including vectors, expression cassettes, and a system for marker gene elimination. This development is reviewed here. For general reviews on plastid transformation see (Bock, 2001; Maliga, 2002; Staub, 2002).

Pal Maliga

Papers

Selectable marker gene and methods of use thereof in transplastomic plants

Removal of plastid sequences by transiently expressed site-specific recombinases

Tobacco Chloroplasts as a Platform for Vaccine Production

Intercellular Transfer of Organelles in Plants for Horizontal Transfer of DNA Expressing Proteins of Interest

Multiple Mechanisms Regulate Transcription in Plastids of Higher Plants