Norbert Martini

Modification of Plant Lipid Synthesis

Genetic engineering of new storage oils and fats has produced oil crop plants with fatty acid compositions unattainable by plant breeding alone. The combination of classical breeding methods with molecular techniques provides new ways for designing oils for food and nonfood uses. Alterations in the position and number of double bonds, variation in fatty acid chain length, and the introduction of desired functional groups have already been achieved in model systems. Short-term prospects include crops such as rapeseed or soybean engineered to have greater than 70 to 80 percent medium-chain fatty acids by content, greater than 90 percent oleic acid, and high erucic acid content, and engineered to form ricinoleic acid in seed storage tissues.

Specialized vectors for gene tagging and expression studies

A genetic approach for the functional identification of genes involves mutagenizing the genome with a known, unique DNA sequence that provides both phenotypic and molecular markers for the isolation and mapping of gene mutations, and the cloning of corresponding genes. The efficiency of a DNA tag as a mutagen is primarily determined by the frequency and randomness by which it can be introduced into the genome of a target organism, and to a lesser extent by its physical or genetic properties that may be modified by genetic engineering. In contrast to base pair exchanges and deletions induced by chemical and physical mutagens that may not result in a complete loss of gene function, insertional mutagens are believed to cause only null mutations by a structural interruption of genes. However, this view is not entirely correct, because insertions in promoters are known either to positively or negatively affect gene expression, whereas insertions in coding regions may also result in gene fusions encoding truncated, but still functional, proteins. In addition, mutations induced by insertion elements frequently cause polar effects enhancing or reducing the transcription of genes located in the vicinity of insertions. It is therefore not by chance that gene tagging by insertion elements is one of the most powerful methods in the molecular analysis of gene expression[1].

Promoter sequences of a potato pathogenesis-related gene mediate transcriptional activation selectively upon fungal infection

SummaryTranscription of at least one member of the potato prp1 gene family, prp1-1, is activated at early stages of potato infection with the late blight fungus Phytophthora infestans. In this paper we present evidence that mRNA encoded by prp1-1 does not accumulate in response to abiotic environmental cues which stimulate transcription of other defence-related genes. Regulatory elements were identified in the 5′ terminal region of prp1-1 by assaying the expression pattern of chimeric promoter/β-glucuronidase gene constructs in transgenic potato. A 273 by fragment comprising the promoter sequence between positions −402 and −130 was sufficient for rapid and strictly localized transcriptional activation at infection sites during the development of late blight disease. Like the native promoter, this truncated promoter did not mediate transcriptional activation in response to other abiotic stimuli. The use of the identified regulatory region to generate conditional mutations selectively at infection sites is discussed.

Molecular cloning of cDNAs or genes encoding proteins involved in de novo fatty acid biosynthesis in plants

Summary In the recent years most of the cDNAs and genes encoding proteins involved in de novo fatty acid biosynthesis have been cloned from various plant species. This includes acetyl-CoA carboxylases, some components of type II fatty acid synthase, acyl-[ACP] desaturases, acyl-[ACP] thioesterases. Comparison of the currently available deduced amino acid sequences reveals regions of possible functional importance. A novel cDNA sequence encoding an acyl-[ACP] thioesterase from Cuphea lanceolata is described.

Expression of Acyl-[ACP] Thioesterase in Cuphea Lanceolata and in Transgenic Rapeseed

A comparison of deduced amino acid sequences from 10 plant acyl-[Acyl Carrier Protein] thioesterases i TE) and their relationship to six Cuphea TEs is discussed. Expression studies of one TE from Cuphea lanceolata (C/TE13) in roots, flowers, leaves, maturing embryos and seeds showed a preferred expression in flowers. Heterologous expression in transgenic Brassica napus revealed 3 % capric acid in immature seeds of the T2 progeny.

Genetic Tools for the Analysis of Gene Expression in Plants

The analysis of gene expression in plants is often based on correlations between data obtained by a variety of means: biochemical, physiological, and molecular genetic studies on the one hand, and classical genetic tools on the other hand. Among the techniques applied to the study of plant genes are screening of various genomic and complementary DNA (cDNA) libraries by synthetic oligonucleotides, gene- or organ-specific cDNAs, or antibody probes, in vitro translation of hybrid-released mRNAs, two-dimensional protein gel electrophoresis, immunoblotting, and transcript mapping (7,10). However, for an in depth understanding of how certain genes are regulated, alternative approaches are needed.

Genetic Engineering of Brassica napus Seeds for Oil Quality and Yield with Toxicological and Motor-Technical Aspects of Biodiesel in Mind

In the temperate climate of Europe rapeseed (Brassica napus, figure 1A) is the most important oil crop followed by sunflower and linseed. Its storage oil is made up of triacylglycerols, consisting of a glycerol moiety esterified to three fatty acyl residues with a chain length of predominantly 18 to 22 carbon atoms.