Enhancing the accumulation of omega-3 long chain polyunsaturated fatty acids in transgenic Arabidopsis thaliana via iterative metabolic engineering and genetic crossing.

The synthesis and accumulation of long chain polyunsaturated fatty acids such as eicosapentaenoic acid has previously been demonstrated in the seeds of transgenic plants. However, the obtained levels are relatively low, indicating the need for further studies and the better definition of the interplay between endogenous lipid synthesis and the non-native transgene-encoded activities. In this study we have systematically compared three different transgenic configurations of the biosynthetic pathway for eicosapentaenoic acid, using lipidomic profiling to identify metabolic bottlenecks. We have also used genetic crossing to stack up to ten transgenes in Arabidopsis. These studies indicate several potential approaches to optimize the accumulation of target fatty acids in transgenic plants. Our data show the unexpected channeling of heterologous C20 polyunsaturated fatty acids into minor phospholipid species, and also the apparent negative metabolic regulation of phospholipid-dependent Δ6-desaturases. Collectively, this study confirms the benefits of iterative approaches to metabolic engineering of plant lipid synthesis.

Towards the production of high levels of eicosapentaenoic acid in transgenic plants: the effects of different host species, genes and promoters.

Eicosapentaenoic acid (EPA, 20:5n-3) plays an important role in many aspects of human health. In our efforts towards producing high levels of EPA in plants, we investigated the effects of different host species, genes and promoters on EPA biosynthesis. Zero-erucic acid Brassica carinata appeared to be an outstanding host species for EPA production, with EPA levels in transgenic seed of this line reaching up to 25%. Two novel genes, an 18-carbon omega3 desaturase (CpDesX) from Claviceps purpurea and a 20-carbon omega3 desaturase (Pir-omega3) from Pythium irregulare, proved to be very effective in increasing EPA levels in high-erucic acid B. carinata. The conlinin1 promoter from flax functioned reasonably well in B. carinata, and can serve as an alternative to the napin promoter from B. napus. In summary, the judicious selection of host species and promoters, together with the inclusion of genes that enhance the basic very long chain polyunsaturated fatty acid biosynthetic pathway, can greatly influence the production of EPA in plants.

Stepwise engineering to produce high yields of very long-chain polyunsaturated fatty acids in plants.

Very long chain polyunsaturated fatty acids (VLCPUFAs) such as arachidonic acid (AA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are valuable commodities that provide important human health benefits. We report the transgenic production of significant amounts of AA and EPA in Brassica juncea seeds via a stepwise metabolic engineering strategy. Using a series of transformations with increasing numbers of transgenes, we demonstrate the incremental production of VLCPUFAs, achieving AA levels of up to 25% and EPA levels of up to 15% of total seed fatty acids. Both fatty acids were almost exclusively found in triacylglycerols, with AA located preferentially at sn-2 and sn-3 positions and EPA distributed almost equally at all three positions. Moreover, we reconstituted the DHA biosynthetic pathway in plant seeds, demonstrating the practical feasibility of large-scale production of this important omega-3 fatty acid in oilseed crops.

Two novel genes are differentially expressed during early germination of the male gametophyte of Nicotiana tabacum.

Two cDNAs were cloned from tobacco pollen by differential display of mRNAs from dry and germinated pollen. Expression analysis revealed that transcript levels of the two corresponding genes were high during pollen maturation, but differed significantly during early pollen germination. One of the cDNAs, designated Arpl1;1, codes for a new member of the auxin-repressed/dormancy-associated protein multigene family. High Arpl1;1 transcript levels correlated with pollen maturation. In germinating pollen, transcripts rapidly declined to minimal levels. The second cDNA, designated Mads1;11, codes for a novel transcription factor exhibiting a novel structure for a putative MADS box protein from plants. Transient expression of a chimeric gene encoding the N-terminal part of Mads1;11 fused to the green fluorescent protein (GFP) in onion epidermal cells revealed that the protein was localized to the nucleus, consistent with its presumed function as a transcriptional regulator. Mads1;11 mRNA abundance was high in mature pollen and, in contrast to Arpl1;1, remained high during 6 h of in vitro pollen germination. The data indicate differential regulation of mRNA concentrations during pollen germination and suggest a function of Mads1;11 protein in regulating gene expression during early pollen tube growth.

The biocompatibility of materials used in printed circuit board technologies with respect to primary neuronal and K562 cells.

Printed circuit board (PCB) technology can be used for producing lab-on-a-chip (LOAC) devices. PCBs are characterized by low production costs and large-scale development, both essential elements in the frame of disposable applications. LOAC platforms have been employed not only for diagnostic and/or analytical purposes, but also for identification and isolation of eukaryotic cells, including cancer and stem cells. Accordingly, the compatibility of the employed materials with the biological system under analysis is critical for the development of LOAC devices to be proposed for efficient and safe cell isolation. In this study, we analyzed the in-vitro compatibility of a large set of materials and surface treatments used for LOAC development and evaluation with quasi-standard PCB processes. Biocompatibility was analyzed on hippocampal primary cells (a model of attached cell cultures), in comparison with the reference K562 cell line (a model of cells growing in suspension). We demonstrate here that some of the materials under study alter survival, organization, morphology and adhesion capacity of hippocampal cells, and inhibit growth and differentiation of K562 cells. Nonetheless, a subset of the materials tested did not negatively affect these functions, thus demonstrating that PCB technology, with some limitations, is suitable for the realization of LOAC devices well compatible at least with these preparations.