Zhu Lihua
Swedish University of Agricultural Sciences, Alnarp, Sweden
Crambe abyssinica is a dedicated oilseed crop suitable for producing industrial feedstocks due to its following unique features: 1) no outcrossing with any existing food oilseed crop, thus eliminating the risk of gene flow from GM plants to the major food oilseed crops; 2) containing 55-60% erucic acid in its seed oil, suitable as starting material for producing very long chain fatty acids or wax esters for the chemical industry; 3) being already commercially cultivated. For these reasons, crambe has been chosen as one of the target oilseed crops in the EU-ICON project. Aiming at developing crambe into a new industrial oilseed crop, we have developed an efficient regeneration and transformation protocol for crambe. Through regulation of some key genes involved in the seed oil biosynthesis, we have obtained transgenic crambe lines showing altered oil qualities and quantities. By down-regulating the FAD2 gene, the 18:1 level was dramatically increased, while the contents of 18:2 and 18:3 were significantly reduced compared with the wild type. The average level of erucic acid in the transgenic lines expressing the LdLPAAT and BnFAE genes reached 70% compared to 60% in the control. When combining all the three genes, the average erucic acid level reached 73% with up to 79% in a single seed. In order to further increase the erucic acid level, we are now modifying some key genes involved in acyl-independent pathway of fatty acid biosynthesis. Through expressing the jojoba genes (either ScFAR + ScWS or ScFAR + ScFAE + ScWS), the content of wax esters in the seed oil could reach 32% to 50% in single seeds in different transgenes in all T4 generations. By down regulating crambe FAE1 and FAD2, we have also obtained transgenic lines with up to 89% oleic acid compared with 16% in wild type. The Southern blot and qRT-PCR analyses showed that the transgenes could be stably inherited in the subsequent generations. The transgenic lines are now under further evaluation for generating homozygous lines. Our results show that, through gene stacking, it is possible to develop crambe into an industrial oilseed crop. Our results could contribute to further elucidate mechanisms underlying oil biosynthesis, thus facilitating genetic modification of oil qualities and quantities.
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