Rapid expression and validation of seed-specific constructs in transgenic LEC2 induced somatic embryos of Brassica napus

Seed-specific modification of crop plants is a common goal in plant metabolic engineering. Ability for early assessment and validation of seed-specific constructs for metabolic engineering in crop plants is desirable. We describe a method in which the Arabidopsis thaliana LEAFY COTYLEDON2 (LEC2) transcription factor is constitutively expressed to generate somatic embryos that can generate a seed-like fatty acid profile from cotyledonary petiole of Brassica napus. We also demonstrate that the super-transformation of 35S-LEC2 construct in B. napus lines that are already stably-transformed with seed-specific constructs producing arachidonic acid (ARA) or ricinoleic acid (RA) in mature seed results in the generation of somatic embryos that actively expressed these seed-specific transgenes and produced ARA and RA similar to transgenic T-2 seeds. Stable transformation of seed-specific construct and analysis of T-1 seed in B. napus requires around 7-8 months. We have used this method to functionally assess single (RA) or multi-gene (ARA) seed specific construct in somatic embryos within 6-7 weeks of transformation and have found the results to be reasonably indicative of mature (T-2) seed fatty acid profiles. A similar strategy can also be extended to induce somatic embryogenesis in oil seed crops for the testing and validation seed specific traits quickly before stable transformation.