Abstracts now available online - Euro Fed Lipid

Accumulation of medium-chain fatty acids in oilseed rape
(Brassica napus L.) due to heterologous gene expression
Christof Stoll* 1 , Wilfried Lühs 1 , M. Karim Zarhloul 1 , Monika Brummel 2 , Friedrich
Spener 3 , Ludger Hausmann 4 , Reinhard Töpfer 4 and Wolfgang Friedt 1
1
Institute of Crop Science and Plant Breeding I, Justus-Liebig-University,
Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
2
Institut für Biochemie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 2, D-
48149 Münster, Germany
3
Department of Molecular Biosiences, University of Graz, Schubertstrasse 1, A-8010 Graz, Austria
4 Federal Centre for Breeding Research on Cultivated Plants, IRZ Geilweilerhof,
D-76833 Siebeldingen, Germany
The fatty acid composition is an important objective of molecular genetics and plant
breeding to make different seed oils more competitive in various segments of the
vegetable oil market. With the purpose to improve the industrial usefulness of oilseed
rape we aim at developing genetically engineered Brassica napus that accumulates
medium-chain fatty acids (MCFA) in its seed oil (Stoll et al., Eur. J. Lipid Sci. Technol.,
107, 2005, 244-248). Therefore relevant genes from the genus Cuphea encoding the
synthesis of MCFA have been selected for Agrobacterium-mediated transformation.
Gene constructs harbouring the β-ketoacyl-acyl carrier protein synthase III gene (wildand
mutant type) either from C. lanceolata (ClKASIII) or C. wrightii (CwKASIII) were
used alone or in combination with different Cuphea thioesterase genes (ChFatB2,
ClFatB3). Compared to the KASIII wild type the mutated enzyme (KASIIIbmut) is not
sensitive for regulatory acyl-ACPs (decanoyl-ACP), and therefore the latter was
predestined to be used in double constructs with thioesterases relevant for the
biosynthesis of caprylic (C8:0) and capric acid (C10:0). The best transformants were
analysed further by half-seed analyses and the number of integrated transgene copies
were determined by Southern blotting. Both single ClKASIII constructs (wild- and mutant
type) showed no effect on the production of MCFA. Concerning the double constructs
an increase of MCFA could be shown in the T2 seeds of which the best phenotypes
were selected to produce individual T2 plants. The resulting T3 seeds were analysed as
pooled seed samples and revealed stable fatty acid contents for both double constructs:
3.9% C10:0 and 12.6% C16:0 for ClKASIIIbmut/ClFatB3 and 2.0% C8:0 and 8.8%
C10:0 for ClKASIIIbmut/ChFatB2, respectively. In order to derive increased levels of
MCFA and to get information about the stability of the gene expression, further
progenies of selected plants showing the best phenotype in the T3 seeds are
developed.