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See detailIncreasing seed oil content in oil-seed rape (Brassica napus L.) by over-expression of a yeast glycerol-3-phosphate dehydrogenase under the control of a seed-specific promoter.
Vigeolas, Hélène ULg; Waldeck, Peter; Zank, Thorsten et al

in Plant Biotechnology Journal (2007), 5(3), 431-41

Previous attempts to manipulate oil synthesis in plants have mainly concentrated on the genes involved in the biosynthesis and use of fatty acids, neglecting the possible role of glycerol-3-phosphate ... [more ▼]

Previous attempts to manipulate oil synthesis in plants have mainly concentrated on the genes involved in the biosynthesis and use of fatty acids, neglecting the possible role of glycerol-3-phosphate supply on the rate of triacylglycerol synthesis. In this study, a yeast gene coding for cytosolic glycerol-3-phosphate dehydrogenase (gpd1) was expressed in transgenic oil-seed rape under the control of the seed-specific napin promoter. It was found that a twofold increase in glycerol-3-phosphate dehydrogenase activity led to a three- to fourfold increase in the level of glycerol-3-phosphate in developing seeds, resulting in a 40% increase in the final lipid content of the seed, with the protein content remaining substantially unchanged. This was accompanied by a decrease in the glycolytic intermediate dihydroxyacetone phosphate, the direct precursor of glycerol-3-phosphate dehydrogenase. The levels of sucrose and various metabolites in the pathway from sucrose to fatty acids remained unaltered. The results show that glycerol-3-phosphate supply co-limits oil accumulation in developing seeds. This has important implications for strategies that aim to increase the overall level of oil in commercial oil-seed crops for use as a renewable alternative to petrol. [less ▲]

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See detailMutan produced in potato amyloplasts adheres to starch granules
Jacon, Géraldine ULg

in Plant Biotechnology Journal (2005), 3

Production of water-insoluble mutan polymers in Kardal potato tubers was investigated after expression of a full-length (Gtf I) and a truncated mutansucrase gene referred to as GtfICAT (Gtf I without ... [more ▼]

Production of water-insoluble mutan polymers in Kardal potato tubers was investigated after expression of a full-length (Gtf I) and a truncated mutansucrase gene referred to as GtfICAT (Gtf I without glucan-binding domain) from Streptococcus downei. Subsequent effects on starch biosynthesis at the molecular and biochemical levels were studied. Expression of the GtfICAT gene resulted in the adhesion of mutan material on starch granules, which stained red with erythrosine, and which was hydrolysed by exo-mutanase. In addition, GtfICAT-expressing plants exhibited a severely altered tuber phenotype and starch granule morphology in comparison to those expressing the full-length Gtf I gene. In spite of that, no structural changes at the starch level were observed. Expression levels of the sucrose- regulated, AGPase and GBSSI genes were down-regulated in only the GTFICAT transformants, showing that GtfICAT expression interfered with the starch biosynthetic pathway. In accordance with the down-regulated AGPase gene, a lower starch content was observed in the GTFICAT transformants. Finally, the rheological properties of the GTFICAT starches were modified; they showed a higher retrogradation during cooling of the starch paste. [less ▲]

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See detailA physiological overview of the genetics of flowering time control.
Bernier, Georges ULg; Périlleux, Claire ULg

in Plant Biotechnology Journal (2005), 3(1), 3-16

Physiological studies on flowering time control have shown that plants integrate several environmental signals. Predictable factors, such as day length and vernalization, are regarded as 'primary', but ... [more ▼]

Physiological studies on flowering time control have shown that plants integrate several environmental signals. Predictable factors, such as day length and vernalization, are regarded as 'primary', but clearly interfere with, or can even be substituted by, less predictable factors. All plant parts participate in the sensing of these interacting factors. In the case of floral induction by photoperiod, long-distance signalling is known to occur between the leaves and the shoot apical meristem (SAM) via the phloem. In the long-day plant, Sinapis alba, this long-distance signalling has also been shown to involve the root system and to include sucrose, nitrate, glutamine and cytokinins, but not gibberellins. In Arabidopsis thaliana, a number of genetic pathways controlling flowering time have been identified. Models now extend beyond 'primary' controlling factors and show an ever-increasing number of cross-talks between pathways triggered or influenced by various environmental factors and hormones (mainly gibberellins). Most of the genes involved are preferentially expressed in meristems (the SAM and the root tip), but, surprisingly, only a few are expressed preferentially or exclusively in leaves. However, long-distance signalling from leaves to SAM has been shown to occur in Arabidopsis during the induction of flowering by long days. In this review, we propose a model integrating physiological data and genes activated by the photoperiodic pathway controlling flowering time in early-flowering accessions of Arabidopsis. This model involves metabolites, hormones and gene products interacting as long- or short-distance signalling molecules. [less ▲]

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